Diagnosis and Repair of Your Imperials's Oil Pump


Imperial Homepage -> Repair ->Engine -> Oil Pump

Question from Jason:

Is there a slick way to prime a new oil pump short of pulling the distributor and using a drill and a rod to spin the pump drive?

On the AMC V-8's I've worked on where the pump housing is integral to the front cover, I packed the cavity full of Vasoline to prime it, stuck the gears in, bolted it back together and was on my way. The Vasoline keeps the air out while the pump spools up, oil comes in, the small amount of Vasoline melts and mixes with the rest of the oil, and you don't have to mess around dialing the timing back in. Of course, I don't see this working on a sealed external pump without splitting it open, which I'd rather not to a brand new unit.

For me the issue isn't so much pulling the distributor, which in itself isn't a big deal, it's getting my hands on a priming rod for a big Mopar locally and
not having to wait for a mail order.

Any ideas?


From Bill:

I've always used the Vaseline method on big block Mopars, works like a charm... just pack it and install it. Do this just before you fire it up, don't rotate the motor till you're ready to start it.

From Steve:

Packing the oil pump with petroleum jelly works well for me but as you mentioned, you'll have to open up the oil pump case to do so. If you decide to prime the engine thru the distributor hole, you'll also have to remove the oil pump drive gear. I run the engine up on TDC before I remove the gear. I made a tool out of a stiff welding rod to reach underneath the gear and lift it up and out of the block. When you spin the gear back down into the engine, remember you have to take in account that it spirals down into place. A large straight screwdriver works pretty good for doing this. I also fill the oil filter with as much oil as I can.

Question from Kenyon (440):

I was driving my '73 today. It has 109,000 miles on it. Has been running well lately. The check gauges idiot light came on, and I watched my oil pressure indicator drop to zero.

The car burns oil. I didn't know this until it burned off some oil during our initial drives together. When the oil gets low, there is a knocking sound that comes from the valve train as it starves. This goes away when the oil is replentished. I think that I hear the same noise, but also imagine that it is maybe slightly worse. It appears that the oil is down a quart, but not seriously low. I'll be topping it off just to be optomistic....coasted the car 1/2 mile home with the engine on but not stressed.

I am assuming that the oil pump has failed.


The wire to the oil pressure sensor is bad.

I seem to recall that there are 2 leads that go into the block and that there is a redundant oil pressure sensor system? There was no LOW OIL lamp lit on the dash.

How do I diagnose this?
What fails on oil pumps?
Can the oil pump be swapped out in the car by just dropping the pan and unbolting the darned thing - putting in a new one?

Anything I missed?


From William:

Good news is the pump is external on a 440. They are reasonable priced. The pump is ...right there where ya screw on your oil filter.

From Demetrios:

It may be a good idea to check the oil more frequently before the oil starvation and subsequent engine damage occurs. Even if the engine does not seize, little by little internal damage is taking place. Also, when the oil pump sucks air, that could help to its demise. If you lose oil pressure, I would suggest to put the transmission in neutral, turn off the engine, and let the car coast down. Your power brakes still work, but you only have one shot at them, so if you apply the brakes, do not release till you are completely stopped.

In most cases, a low oil pressure indication is most likely due to a bad sending unit, but don't risk it. If the warning is real, you will hear the lifters.

Question from Jason (440):

I took my '68 Crown on my first short road trip this weekend, and after probably two hours of smooth cruising at 80 on the highway, I glanced down
and noticed my oil pressure gauge had dropped from the middle to the left-most end of the 'acceptable' bar. After getting off the highway, and driving in city traffic, the gauge continued to stay in the same spot, and not hearing any clatter I figured the sending unit was probably shot. Unfortunately though, when I started the car this morning it seemed to clatter for a few seconds, and then the gauge returned to the same spot at the left end of the line. The car sounded fine, and I drove it back home, but I went to restart it this evening after letting it cool down, the gauge didn't even make it to the bottom bar and the valve clatter was awful, so I shut her off. The oil level is fine, and it doesn't smell like gas. [I doubt I would have gotten fifteen to the gallon on the trip back if it was running rich enough to cause a problem with oil thinning.]

The car has 52k on the original motor, but hasn't been driven all that much in the last ten years. It's probably been about 300 miles now since I changed the oil before I left [with straight 30 weight castrol.] The man I bought it from had changed the oil with 10w30 right after I bought it, but it turned black
within 250 miles and I changed it to something that wasn't as thin.

I'm still rather new to the fine points of the mopar big block, so I'm not really sure where the weak points in the oiling system are. How hard is it to
kill an oil pump on a 440, say by giving the car a good workout after it sat unused for a while? Also, on the off chance something is clogging the pickup,
how much of a nightmare is it to get the oil pan off with the engine still in the car?


From Roger:

Pull your oil filter and dump it it a clean glass jar. Let all of the crap come out of the filter. Then filter the crap through cheese cloth and see what is in it. Metal bad sign, black lumps is the type of oil you changed too. Differnt manufactures use differnt additivies. If the oil fill cap is clean this should not happen (black gunk on the oil cap shows lack of oil change). I bought a '62 Mercury Comet with a engine 35,000 miles on it. A guy at the neiborhood gas station told me to switch to Delo Diesel oil so I didn't have to change as often. I lost oil pressure, smoked and rattled in 45 miles. I was later told that a engine must have Parifin build up in it to seal the rings, bearings ect. The Delo cleaned that out and it ruined the engine. Rule of thumb always use the same oil in the engine that was used before. Brand name I mean. Weights of oil dont make much differnce. Watch out for synthetics and oil additives too. I hope your OK with your eninge. I was lucky on my 55. It has all of the oil filter service stickers from the dealer and gas station. They use chevron in the car from the day it was new and I still do. No problems to date and I drive it a lot.

From Dick:

It is quite possible that your pressure relief valve in the oil pump has stuck in the open position, probably due to a burr on the valve or a piece of crud in the valve. Before you take things apart, just take the oil pump off the engine and inspect the parts, and make sure the pressure relief valve is free to do its job. I had this exact same symptom on my '69 LeBaron when it was nearly new - scared the wits out of me, but that was all the problem was (a burr on the valve) and once cleaned off, the problem never recurred all the years I owned the car.

Question from Paul (440):

Is there an easy way for me to tell if my oil pump is working?


From Kerry:

Two ways: 1) Purchase a 15 buck oil pressure gauge and hook it in where the sending unit is. This is probably the easiest. 2) Another is to pull the valve cover and see if oil is making it to the rocker arms. You will have to replace the gasket however.

From Phil:

Yes, just unhook the coil wire, then unscrew and remove the oil sending unit. Should be down by the fuel pump on the passenger side of the motor. Crank the motor over and see what happens. While you can see oil come from there, I usually keep a cheapy mechanical oil pressure gauge I can hook up temporarily to see what the actual pressure is. If you have no pressure there, then that motor needs looking into.

From Leo:

This is what I do if I suspect mechanical failure. Take out the oil filter and cut it open with a pair of tin snips, then shine a bright light in between all of the pleats and look for shiny bits of metal. If you don't see any there, drain the oil through a cheese cloth and check for metal there. If it comes out clean, you might get away by replacing the oil pump or drive. If you have metal in either place, it's engine tear down time.

From Robert:

Just happens that I changed an oil pump today. It is easy. It will be necessary to unbolt the engine mounts and jack the engine up an inch or two. Then just remove the four bolts and the old pump will come out with ease. Be sure to prime the new pump before installing it. That is all there is to it.

From Mr. Dave:

Put a pressure gauge in place of the oil censor on the engine. If you read about 15 pounds when engine idols, your pump is OK.

Question from Bob (440):

I have found my oil leak. It is not the rear seal it is the little round sending unit on the back of the motor. The problem is I can't figure out how to get it off. None of my sockets will fit on it and I can't get a wrench on it either. Any help on this would be great. My Imperial is a '68.


From Kerry:

Try a basin wrench from your plumbing supply. I've also reached them from below and by lying on the motor and doing it by braille.

From Larry:

There is a special socket for these sending units. It is available from Sears or most tool suppliers.

From Mikey:

Most of the replacement oil sending units for gauge equipped cars have a square shaped part at the top of the threaded stem or nipple that threads into the block, you cant see it well because of the bell shaped portion of the sender is above this part. As I recall they are about 1/2 inch square. On a 383/400/413/440 if you get the air cleaner out of the way and situate yourself just so you can see how they are built. A shortie wrench will usually do the trick.

From Kenyon:

There is a special socket for oil sending units that most mechanics will know about. I left a C-note as collateral with the guy in the grease pit down the street and borrowed his. I think that I saw one in a parts shop by Lisle in the red and white packaging on a cardboard card hung on the wall.

It came right off when I used the right tool.

Question from Roy (440):

I have been looking at the oil pump section of the FSM and I would like to get some clarification about what is not written in the FSM. The oil pump comes after the engine removal section of the FSM, but I can't see any reason why it can't be removed from the engine in the car, am I correct? Next from the picture, the shaft is pinned to the distributor gear and is slipped in from the distributor side, so it can't accidentally slip out when the oil pump is removed, correct? I just don't want any surprises!


From Peter:

The oil pump *can* be removed from the engine while the engine is in the car (at least on a 70 Imp). Access to the mounting bolts isn't terribly easy, though, and you'll probably have to remove the motor mount bolts and jack up the motor a bit. Also, the oil pump input shaft housing protrudes into the block about 2 or 3" (going on memory here) and is o-ringed. You'll need that clearance below the pump to lower it enough to get the input shaft housing out of the block. I recall rotating the pump housing (after removing the filter) to find a position where I could remove the pump. Regarding the pump drive shaft... The gear is pressed onto the end of the shaft, not pinned. The result is the same, though. The shaft rides in a bushing pressed into the block and will not drop out when you remove the pump. The distributor must be removed to remove the pump drive shaft. If you intend to remove the shaft (which isn't necessary to replace the oil pump), follow FSM procedures for positioning the crankshaft. Otherwise the distributor rotor will probably be out of whack following reassembly and your carburetor will turn into a flamethrower!

From Mark:

Yep, the pump can be removed with the engine in the car without too much difficulty. ESPECIALLY in an Imperial. The external oil pump is one of the more elegant design aspects of the big-block MoPars. (And is shared with all the MoPar in-line sixes and eights.) And, like Peter wrote, that shaft is not going to come out, unless you remove the distributor and pull it out from the top.

Question from Roger (440):

Where is the oil pump located on the engine ? Is it possible to get an electric oil pump for the 440 so you can lubricate the engine before starting?


From Mark:

On big-block MoPars, the oil pump is mounted outside of the crankcase, on the left (driver's) side, low and just behind the timing cover. It's where the oil filter spins onto. (And, I believe, helps contribute to quick filter re-filling when replaced. This helps extend engine life.) Most other engines made in the world have the oil pump mounted on a main bearing, inside the crankcase. The benefits of an outside oil pump include ease of service or replacement. There're rarely any clearance issues should one decide to install a high volume unit. In fact, MoPar used to supply a kit to modify the existing pumps, and many guys I know would install the kit without even removing the pump from the block! Try THAT on a Chevy! 

I've never heard of an electric oil pump, though it wouldn't surprise me to learn of one. I've seen a couple of pre-oiler systems, mostly at the autocross course for those cars that pull so much g-forces through the quick turns that all the oil has sloshed out of the pan or has been pumped up into the upper block faster than it can flow back into the oil pan. Basically, it's a cylinder that's capped on one end with a spring-loaded piston on the other. Oil comes through a valve into the sealed end, pressing the piston against the spring. At a determined drop in oil pressure, the valve opens up, and allows the piston to push the oil back out of the cylinder into the oil system. I've seen a couple of these systems set up so that the driver can trip the valve from the dash before starting the engine, thus allowing it to start with oil pressure already present.

From Steve:

The oil pump on B(361,383 and 400) and RB (RB=413,426 and 440) is located in front of the drivers-side motor mount and is kind of square looking. The oil filter actually screws onto the oil pump. The pressure relief spring is located under a large nut that is at the rear of the pump and faces the motor mount. A far as I know....there is no electric one available and it's value would be negligible as far as I am concerned. It has also been mentioned that the oil pumps are the "weakness" with these engines. I would have to say that it isn't so even though the oil pump relief spring stuck on my '73(three) Imp on it's trip home on the day that I bought the car and needed to be towed home. It came unstuck as I was driving the car into the garage to replace the pump but I replaced the pump anyway. It is much easier to change than the Chevy or Ford pumps since it is externally mounted.

Question from Bob (440):

I have 67 Imperial convertible. The oil pressure gauge reads about a quarter ways inside the left side of the safe operating level. I suppose this is an acceptable reading but it flirts with the edge of the low line after long runs.  What kind of readings are some of you other members getting? I was considering a motor flush for a possible restricted oil screen.


From Steve:

I would first suspect the gauge is not correct or replace the sending unit before suspecting that you have engine problems. If you are guessing the oil pump pickup tube screen is clogged, most likely the most thorough way to solve this problem is to drop the oil pan and clean out the screen and the pan. <--my .02cents Motor flushes might dislodge more varnish and sludge and clog the screen even more. You did not mention if you are getting a "low" reading when hot and at idle. An oil pump story: When I first bought my '73(which has been dead for some time now) the oil pressure dropped to "zero" on it's first ride to my house. The lifters started ticking and I started to hear "low end" knocks, so I shut it off and had it towed home...knowing full well that the gauge was NOT lying. I bought an oil pump which is easy to install since it is "external". I briefly started the car up just to get it in the garage and all of the sudden it had lots of oil pressure. I replaced the pump anyway and disassembled the old one only to find worn rotors/shafts and semi-stuck pressure sleeve and spring. The problem never surfaced again with the new pump. (end story, food 4 thought) Also, I neatly installed a small, quality (Auto Meter), mechanical oil pressure gauge neatly under my recent '75 Imps dash along with other gauges(H20 temp, volts, vacuum, and trans-oil temp.) The gauge reads about 65+psi when on high idle when cold...and about 25 when hot and idling in gear. '75's unfortunately don't have a factory oil pressure gauge..only a light. (thumbs down goes here) I use Castrol 10W-40.

Follow-up from Bob:

I kind of played with the wire connection on the top of the sending unit and it was kind of loose. Don't know if that could be a factor, but the readout is a little higher now. First day start idle is almost in the center of the the readout, hot idle dips down to about 25% of the readout towards the low end. Still in the acceptable range but it just seems like it should be higher. I stared running red line 20-50 a few weeks ago. Could have something to do with it also. I'll switch oil again before I do anything mechanical. On the 75 imp with the dummy light, how low does the oil pressure have to go before the light comes on? Also does anyone know the difference between a high volume oil pump a high pressure oil pump, and the standard unit? It seems self explanatory but I wasn't sure.

I was told by a parts store guy that you must raise the engine block up slightly to install and I imagine remove the oil pump. Is this correct, and thanks for the clarification on the oil pump types. As I said before I'm going to change my oil from red line 20-50 to something more nominal and see what happens before I make any mechanical moves. I know the redline is super thick at start up and runs a little different.

Reply from Steve:

Your oil pump is located on the left (driver's) side of the engine directly in front of the motor mount. If you don't have 3 or 4 inches of space between the pump and the frame...then you will have to disconnect the motor mount on that side and jack up the engine to have enough clearance to slide the pump out. If you decide to do this, be careful to watch the cooling fan as it will come close to the shroud. When I did it on my '73 many years ago, I also disconnected the throttle and kickdown linkage so that it wouldn't get bent. No big deal. As far as changing the relief spring in the pump...the cap/nut faces rearward towards the motor mount. You'll need about 2 inches of space to change the spring. How many miles are on your Imp anyway. Did you change the sending unit?

From Mikey:

And for standard, hi pressure and hi volume pumps: the difference between standard and hi pressure is the relief spring, the factory used a 55 PSI spring for standard. A high volume pump moves more oil by volume than a standard one, but not necessarily at a higher pressure. The general rule of 10 PSI per 1000 rpm is usable for most engines, so standard pressures should be fine. as a final note on the pumps, the pump will move a set amount of oil per revolution of the pump, its the clearances between the shafts and bearings in the engine and the viscosity of the oil that determine the pressure. If an engine is well within its limits of bearing clearances ( main, rod, rod side and cam ) then your oil pressures should be adequate. Usually changing from a 10-30 to a 10-40 ( for example ) won't make a huge difference.

From Peter:

The oil pump cover on my 70 LeBaron had a hairline crack and, therefore, an annoying drip. I replaced the pump with a new standard pump and *did* have to raise the engine. The pump has a cylindrical protrusion that is about 1" in diameter and 2 or 3" long to house and support the pump rotor shaft. You have to drop the pump down far enough to get the protrusion out of the block.

Question from Mike (440):

My 1970 Imp needs to have the engine pulled because of a blocked oil  passages..... ( at least that's what he says ) ... The problem is , there is VERY little oil pressure... He pulled the pan and cleaned up the oil screen and drop tube... ( which was plugged up too ) and still low oil pressure... His guess was the oil passage around the cam area..  Does that sound right ?  


From  Pete:

Here's a little info that you may find useful. I've rebuilt several engines and always make a tool for "pre-oiling" the engine prior to the first startup. For Chrysler engines I obtained a spare 440 distributor and oil pump drive shaft. The oil pump drive shaft has a hex drive at one end (it fits into the oil pump) and a big gear at the other end (it meshes with a gear cut into the front end of the camshaft). I took a bench grinder and ground all the teeth off the oil pump drive shaft. Then I stripped the distributor down to the housing and shaft (advance weights, points plate, & points cam all removed). These modified parts are then installed in the engine temporarily and I hook up a 1/2" drill to the top of the "distributor." Presto! I can run the drill to pressurize the entire oil system without running the engine. I usually do this before I install the intake manifold to verify that all the lifters are getting oil, but you don't have to. If you pull the valve covers you can also verify that the rocker shaft tubes are getting oil. On an engine with some sort of oiling problem, this setup allows you to add engine cleaner or kerosene or whatever solvent you want to the crankcase and loosen up/flush out the system without worrying about piston scuffing or bearing wipeout. You just drain the solvent and change the filter, then add fresh oil and a new filter and run the pump again for a bit to make sure that everything gets a good shot of oil before you reinstall a good oil pump drive shaft and distributor. You can also hook up a real oil pressure gauge and know what pressure will exist before you ever turn the key.

From PEN:

Before you pull out your engine, consider that a low oil pressure reading can come from one or more of the following: a faulty oil pressure sending unit, a wrong dipstick, diluted oil, the oil pump pressure relief valve stuck open, a cracked, loose, or bent oil pump suction tube, a clogged oil filter, or least likely worn engine bearings. Your mechanic said that the oil pump screen and suction tube were clogged, but with what? And if that were true, how could that "what" have made it up, through the filter, into the cam passages? If you really have very low oil pressure, then your engine will produce a great deal of noise just running. The lifters would produce such a racket that you would shut it down after a matter of seconds. On the other hand, and some may dispute me on this, if your engine runs and you get no lifter noise, then you are getting at least enough oil pressure to protect and run the engine. There is something, in my opinion, that just doesn't add up in what your mechanic has told you.

Follow-up from Mike (Car also has noisy lifters):

Well the lifters do make noise... So I do have legitimate low pressure to the top end... What worries me is it seems to be on both sides... Don't know that for sure... The rest of the motor is getting oil.... Even have oil up to the rocker covers. (?) I'm looking into other possibilities... 

Reply from Kne:

Some other possible reasons for noisy hydraulic lifters: Oil too low. Oil too high. Oil too thin....I hope you are not using the same water-thin oils that are being used in new cars. Oil too old. ("prolonged use of oil") Oil pump relief valve stuck. Air entering oil pump. (Oil screen/pick-up too high, leak in suction tube, loose oil pump cover.) Water or gas in oil. (especially anti-freeze) I would suggest an oil change before doing anything, and see how it sounds with fresh oil. If you just have an oil light or electric gauge, it may not be giving a true picture of what your oil pressure is actually doing. If so hook up a temporary gauge.

From Steve:

I'd sure try a high volume oil pump first. Unless the engine was terribly neglected, I doubt the passages are just plugged. I've seen some bad machining that caused low pressure (I'll share the details with those interested) but if the engine made it to 105K miles, she should continue to run for a long time. Big Mopars don't need a lot of pressure to be happy, just a good supply of oil. 10 PSI at idle is a little scary to see, but enough for the 440. I drove a 383 for years with real low oil pressure, and the crank in my 451 had an oil passage drilled right out into space... the 440 lived a long life before that! A good rule of thumb is 10 PSI per 1000 RPM. If the rockers aren't clacking at idle, keep a fresh supply of oil in the crankcase and enjoy driving the old girl!

From Norm:

Try the oil pump.  They are notorious for failing.

From Rolland:

It has to be extremely rare to have the oil passages plug up and not have any oil pressure. I have never heard of this. I would replace the oil pump, the sending unit, and check the rod and main bearings before pulling the engine. Were the rod and main bearings looked at when the pan was off?

Follow-up from Mike:

The rod and mains look good and are getting oil... He says there is a passage to the top end that's plugged... I guess it sounds ok, but I'm thinking their must be some way to clean that out short of a rebuild...

Question from Ben (413):

I am thinking about replacing the stock oil pump on my 64' Imperial (413 c.i.d.) with a new Mopar Performance hi-volume model. The engine has about 83,000 miles on it and runs great though the oil pressure is a little slow on the rise after being started. My question being, will it cause my engine any harm to use a hi-volume pump in place of a stock unit?  I'm looking to better protect the engine and have been told not to use the hi-volume model for fear of bearing damage. It this correct or a load of B.S. ???? 


From Mark:

I think a high volume oil pump is a GREAT idea on most all engines. I can't think of one drawback. (Other than the extra expense and the trouble it takes to install.) I've had one on a '66 Plymouth with a 383 since the rebuild about 13-years ago now, and that engine now has over 115,000 miles, and doesn't use a drop of oil. I installed it specifically to have as much oil pressure as soon after a cold start as possible. As most anyone who's been around the mechanical side of gasoline engines knows, study after study shows that something like 75% of all engine wear occurs in the first minute of initial, cold start up. And I've installed high volume pumps on a whole bunch of other engines, most non-MoPar, foreign and domestic, to no ill effect what-so-ever. What CAN cause trouble are high PRESSURE oil pumps, and I think this is where people who advise against high volume oil pumps get confused. A high pressure pump can pump oil in such a way as to damage the low end and cam bearings. Unless an engine has been designed for one, do NOT get a high pressure pump. In my opinion and experience, Ben, a high volume oil pump would most certainly solve your slow-to-rise oil pressure problem. (Though, also know that the oil pressure gauges on these cars aren't the most responsive....)

From Pete:

Maximum engine oil pressure is limited by the pressure relief valve in the pump. If engine bearing clearances are correct, installing a high volume pump (with the same rating pressure relief valve as the original pump) will simply cause more oil to dump directly back into the oil pan (or pump inlet) instead of flowing through oil passages. Pressure won't be affected. No bearing damage will occur. If engine bearing clearances are excessive, a high volume oil pump will force oil into the oil passages faster than it leaks out of the bearings. So, a high volume oil pump can be used as a Band Aid for a worn engine. Unfortunately, there's a down side. Oil leaking from worn connecting rod and main bearings will be thrown onto the cylinder walls faster than the oil control rings can wipe it away. High oil consumption will result. Bearing material is relatively soft and CAN be damaged by prolonged, excessive pressure. So much oil flows through the bearing/crank interface that it carries away bearing material. This can be caused by someone shimming the stock pressure relief spring or replacing it with a stiffer one. I once put a 400 engine in a Firebird for someone (he supplied the engine). Unbeknownst to me, he had installed a few flat washers behind the pump pressure relief valve spring to boost oil pressure. Boost it, it did! When I fired the engine for the first time the oil pressure gauge spun all the way around. Then, when I revved the engine, the oil filter literally exploded. What a mess! I wouldn't worry too much about a slow-to-rise oil pressure gauge. After all, on any Chrysler big block, the sender/switch is about as far away from the pump as you can get. Oil reaches the crank and cam long before it gets to the sender/switch.

From Leo:

Mopar Performance has a high pressure relief spring part #P4286571, which delivers up to 70 PSI with your existing pump. You can order it from your Mopar dealer.

From Mikey:

In all my engines I use hi volume pumps. Its the clearance in the bearings versus the amount (volume) of oil that the pump can push that gives you the pressure anyway. I believe the stock relief valve rating is about 55 PSI, Mopar Performance has a higher rated one also. One thing I have noticed, I have very little variation between cold and hot oil PSI as a result of this, and the pressure always comes up quickly on initial startup.

Question from Rob:

My oil pressure gage is slow to come up to its normal position.  Prior to having my oil changed last week, the needle would immediately and steadily move from the left to near extreme right when I start the engine. This has been so for the 2 yrs I have driven the car. Now the needle 'sluggishly' comes to lower side of half way and the slowly moves to the position I have observed as normal when I start the car. The performance is similar to extreme cold engine starts (-30C).  The first thing that comes to mind is defective filter. The place I  had my oil changed recently changed brand names (to Fram, I think), has anyone had or heard of a defective filter? The second thing is too heavy an oil for the temp, but this seems unlikely as the temp is still just above freezing ... hardly enough to 'thicken' oil ... and the oil is supplied from a 500 gal drum stored inside. The sending unit? Weak oil pump?


From Dick:

I am not personally familiar with 66's, but if it has an electrical gauge, the indicator should move up the dial in slow, pulsating surges, perhaps 1/4 of the way to its steady state position with each surge, which should occur about once per second. This is the gauge regulator doing its job, and is normal. If it used to fly up scale immediately, it is either not an electrical gauge and you had very thin oil, or there was something wrong. A slow reaction is pretty normal, even for the other type of gauge, which I call "mechanical", even though it is more properly called hydraulic, I guess. In any case, see if your gauge sender has a wire on it. If so it is electrical. If it has a tiny tubing on it, it is mechanical. Others on the list with a 66 will probably jump in here with the answer to this. Not knowing what part of the country you are in, I cannot comment on the oil you are using, but consult your owner's manual, don't trust the guys in the Quickee-Lube places. If the oil pressure is actually in the normal range when the car is thoroughly warmed up, there is nothing wrong with your oil pump, or anything else mechanically. I cannot fathom why a Fram or other name brand filter would be causing this problem, but I suppose if it is draining dry between starts, it could cause a slow rise of oil pressure. It would be wise to change the filter again, just to eliminate it as a cause. They only cost a few bucks, and you might save yourself a lot of unnecessary wear on startup if you got the one in a million that has a bad check valve.

From Bob:

A defective filter is a possibility. Somewhere I've got tests of oil filters, which included disassembly to check construction and there were surprising differences between them. I recall Fram was not on the top of the list.

From Norm:

This is the way all of the ones I have owned (10) have operated . If there is a problem, the filter could be involved as could be a dirty and/or erratically operating filter bypass spring in the oil pump. This sometimes responds to a " technical tap".

Question from Mark:

I had my car up on a rack, and while the guy was doing the transmission work, I think I found a leak.  It appears to be leaking from a bolt that holds the oil pump onto the block - at least it is back there near where the pump connects to the block. (There's the filter, then a curved pipe looking thing with a plate on it with about 4 or 5 bolts.)  OKAY, the question is: is there a gasket there?  Could it be as simple a matter as tightening that bolt???  Is there any way I can avoid replacing the whole dang pump?  Anybody have experience with leaks here?


From Richard:

Pull the pump and replace the gasket yourself. Three bolts hold the pump to the motor and replacing this gasket is only marginally tougher than replacing a fuel pump gasket. 

The first rule of chasing oil leaks is start from the top-front of the motor and work down and back. The second rule is start w/ a clean motor. I like Gunk brand engine cleaner and degreaser products. With enough cans, patience, rags, and a garden hose, you can get your motor and surrounding areas very clean and dry. A pressure washer helps. Repeated applications are generally required. If you've had nasty leaks for long periods of time you'll also have a ton of road dirt stuck to the oil. In this case, scrapping some of the thicker spots w/ a putty knife is helpful. Once you get the old stuff off, it's a lot easier to see where the leaks are actually coming from. This is especially true w/ the front of the motor as the fan and pulleys tends to blow things around. It wouldn't surprise me if you're oil pump leak was actually a valve cover leak running down the front of the block. One last thought: oil and rubber don't mix. While degreasing, inspect your radiator hoses, power steering hoses and motor mounts. If they've been soaked in oil for any period of time, replace them.

From Bob:

Yes there are two different gaskets in there. The first gasket is between the block and the pump assembly and the second is between the two pump rotor housing halves. If the leak is the pump to block gasket you have to take the pump off anyway and if it is the housing halves gasket you have to take the pump apart anyway. If you buy a replacement pump you will get the gaskets with the pump and have a new pump to boot. 35 to 45 dollars for a new pump. Up to you but if you have to pull the pump anyhow.....

Question from Mike:

What's a "windage tray"? And why is it called that?

Reply from Joe:

A windage tray is used in engines that are used for hard acceleration like in racing. Windage trays are positioned between the oil pan and the block, they help keep the oil in the pan so the mains, throws and the oil pump pick-up have oil to pump. When high RPM, hard launching cars leave the line the oil is sloshed backwards and whipped up into the block by the crankshaft, so the oil is not available for the oil pump to pick it up.....not a good thing at 6,000 RPM.

Question from Zan (413):

 My engine is making some bad noises and I have low oil pressure.  Any ideas what the problem is?


From Brad:

Low or unsteady oil pressure unaccompanied by overheating and nasty noises, is most probably due to an electrical fault. Check the pressure directly with a gauge. If you don't have one try replacing the sending unit. My '66's gauge would inadvertently drop to zero and then back up to "normal". I checked the wiring and then the sending unit. The sending unit turned out to be my problem. Try turning the body of the sending unit by hand. If it turns, it's bad and will at some points ground the circuit. A $12 replacement will prove if it's at fault.

From Denis:

This happened to my LeBaron, and I ended up replacing the oil pump which is easy accessible, and not to difficult to install. Good oil pressure now.

Question from Cory (413):

When I got my 65 LeBaron it had 10 year old oil in it so I bought some engine flush, flushed the engine and then added 10w30 Mobil 1 full synthetic(6 quarts right?) After doing all that I've notice that my oil pressure is lower than I'd like so I have decided to install a new oil pump since they are so easy to get at (no pulling the pan). Should I go with a stock pump, a High Volume pump, or a High Pressure pump? 


From Bill:

If you feel you must replace the pump, then just go with a stock one, unless you're spending weekends at the drag strip.

From Joe:

I have a high volume, not high pressure. It also acts as a coolant to run a lot of oil through her. I also run an oil cooler because of living in Palm Desert. I run 2 trans coolers. On the Imperial gage, I have the needle about 7/8 pressure from left to right. It was about half before. You only need about 10 pounds oil pressure for every 1 thousand RPM's anyway. I started using Mobil 1 13 years ago because till I learned how to lower the pumps of my engines here in the desert, I needed to stop my engines from cooking the oils that are called the conventional oils. They would fry around the heads and deposit a filmy black burnt substance there. Now, my engines are as clean as when they were new even after 125,000 miles. I change it every 5 thousand on the 5, 10, 15 20 thousand scale.  I use it also in my 525 Horsepower 69 Daytona. This 69 engine now has 83,000 miles as of last week. I asked the engine shop if we should pull and freshen it up, as I have driven it up to 180 MPH and they asked if the oil consumption has changed and it has not since new. The smog device sucks out some of the oil at high rpm, but no smoke or smell exists. They said leave it alone for now.

Question from Steve (1981):

My '81 Imperial oil pressure light came but the oil is up to level. I hear tappet noise and my car sat for about three weeks. Help!!


From Dick:

This (no oil pressure coupled with valve lifters suddenly ticking) is a very serious situation. Either your oil pump is not pumping or you have a spun bearing. Either way, you have to drop the pan and take a look at things. Do not run the engine at all until you do this. If you're very lucky, you'll find the oil pickup float has fallen off or the screen is blocked. More likely, there is a spun bearing - since you don't hear any rod knock, it is most likely a main bearing. While you may be able to patch this up and get a few more miles out of the engine, the right way to do this is to plan on a complete engine rebuild. Sorry, this is bad news (unless, like me, you enjoy rebuilding engines!)

From Joe:

Dick is right about dropping the pan, but I would like to add another reason for no pressure. Your Imperial uses the 318 - the distributor gear in this and other Chrysler V-8's are driven off the camshaft - the distributor's shaft fits in a slot on the top, and a hex shaft going to the oil pump on the bottom. Although rare in a relatively low-stress application such as this, the hex shaft has been known to strip, or more commonly, break off at the pump. My guess is some form of debris might have found its way between the inner & outer rotors of the pump(not much clearance in there) and when you started up the engine, this particle jammed the rotors and the shaft twisted off. Freak thing, but possible.

In addition to checking the things Dick told you, pull the distributor(mark it's position first!) then, noting it's position as well, pull out the distributor gear. If there's no hex on the end, that's your problem. If you don't check that gear, AND your oil pump, you won't cure your problem. My suggestion, while you have the oilpan off anyway, which is necessary to get to the pump-located on rear main bearing cap-take the oil pump off, DISASSEMBLE it and CHECK it for debris, wear, burrs on the rotors, and clearances between inner & outer rotors. Checking these things will ensure everything working right upon re-assembly.

From Jeff:

Many times the shaft shears off at the very bottom tip area. The camshaft still turns the rest of the shaft, including the top half which turns the distributor.

I have seen it happen several times on 318s, curiously the ones I have seen have all been early '80's units. I have found that a large piece of debris gets into the pump and locks it up. The shaft then shears.

So, even if that is the problem: sheared oil pump drive shaft, the oil pump & pickup will need to be replaced. If the debris somehow dislodged after the shaft sheared, you could get lucky, but I would expect the oil flow to pull it back in.

From William:

The oil pump shaft on my '81 LeBaron sheared off a few years ago. It ran for about 15 seconds after the light came on (70mph on the freeway) as the broken oil pump shaft does not interfere with the engine running. After removing the pump, it was in fact seized, it appeared to be from many years of small debris packing into a thin film in the corners of the rotor (valve seals probably). I replaced the pump and shaft, thinking I was pretty clever. I checked the main and rod bearings, they seemed ok, so I fired it up. Still no oil pressure. After a frustrating weekend of trouble shooting, I traced it to a spun cam bearing, blocking oil flow. I just junked the motor and dropped in a hot 360. Anyway, might be food for thought.

Question from Jack (318):

The basic facts:

'81 Imperial 

85K+ miles 

New Timing chain 

New 4bbl Carter 

non original exhaust, no cat, no resonator 

I just had a bunch of work done on the car; and am driving around the city for the first time since I got it. It came with an aftermarket mechanical oil pressure and temp gauge. Now after I picked it up, and fed it a can of CD-2 to quell the nasty lifter noise, I have a chugga chugga sound when I accelerate. As if one cylinder isn't firing, or valves aren't closing??? It idles quietly, but the chugging sound is quite un-Imperial-esque.  Check exhaust manifolds for loose bolts? It still does feel like it's missing sometimes (I'm installing new plug wires, and doing a compression check this weekend) 

Oil Pressure> almost 0 on the gauge when warmed up , in gear, foot on brake. It goes up over 50 when just started, and seems to run at least 10psi per 1000rpm when at speed, but scary low at idle when warm . (I spend as little time as possible there!) The options seem to be: install new gauge to be sure of readings.. (like the mechanical/flex hose thing suggested in the archive) new oil/ filter, (was just changed, but with the CD-2 (detergent/clogged filter?) and put in synthetic? new oil/filter, and put in straight 30 wt ? 50 wt? Drop the pan, and make sure all of the ex timing gear nylon isn't blocking the screen? new oil pump? Drop in a new 440 crate engine? (ok, just a thought....) There don't seem to be any audible signs of engine distress, (loud valves, bearing knocks, etc...) so far.. The temp gauge reads a consistent 260 degrees, but it reads 190 when dead cold, so I figure that's just old funky gauge stuff. Any thoughts much appreciated. Could I have caused any damage, driving the 100 some miles when the timing chain slipped?


From Matt:

The low oil pressure is probably due to excessive wear. Although in my experience the cam bearings are not a Mopar weak spot.( Maybe a GM problem with their notorious butter camshafts). On a 360 in a 79 New Yorker I had, the problem was worn connecting rod and main bearings. The chugga problem and the suspected miss at idle seem to me to be lo compression symptoms. Possibly a burnt exhaust valve. The compression test is definitely recommended. The temp gauge irregularities may be due to the sender. Does the after market gauge hook up to the factory sender? If it does ,this could be the problem. The Imperial used a different sender than other cars due to the digital dash I believe. I've heard of this being a problem with engine swaps in these cars. 

From Kerry:

Some thoughts. First, regarding the Chugga... Does it sound off when you put it in gear, stand on the brake, and give it some gas, or only when driving? If you can get the noise to repeat when not moving, have someone help you and stand beside the car with the hood up and pinpoint where the noise is coming from. Exhaust leaks have many different sounds. The 4' piece of hose trick that Dick B mentioned works quite well. Second, regarding the oil pressure. My friend, I think your engine is about worn out. Of course, pick up another oil gauge and check to be sure but what I expect you will find is what you already saw. What this means is that some bearings (1 or more, probably more) have excess clearance. Or perhaps a weak oil pump. Blockage will normally show low pressure all the time. Solutions, several and none that good. I frequently run straight NON detergent 50 Vavoline Racing oil in my low oil pressure or oil burning cars. Makes them hard to start but the increased viscosity seems to increase oil pressure. I'd probably try 30 or 40 weight first. There are also some "molasses" like oil additives which increase oil viscosity but I would trust Vavoline more. Final solution is a bottom end rebuild. 

 Tips from Dick:

The oil sending port is the same on virtually all engines. Next to your distributor you will see an oil pressure sender screwed into the block. Verify this to be sure, but I am pretty sure it will have 1/8 pipe (AKA NPT 18) thread. Most commercially available direct reading gauges (the hydro-mechanical type) have this same thread, so if you are agile enough to read it there, you can just thread it into the same hole. It makes it a little difficult to read that way, but that is all you really need. If you want to go more deluxe, go to the rack where they sell replacement and accessory fittings for grease guns and buy an extension hose - they will usually have one at least a foot long in stock. Verify that it is the same thread, and you might have to buy an adapter to get the sex and/or the thread right (some did use 1/4 pipe also), but it should thread right into the block, and perhaps via a female to female adapter, into the gauge.

I wouldn't look for this stuff at Sears, but rather at NAPA or another store where they cater to real mechanics. They will also have an oil pressure indicator in stock; you will probably have to buy a kit which includes a hook up line and a mounting bracket for the dash, all of which you will promptly discard, but they are pretty cheap even with all the doo-dads. They will also have any adapters you will need. Be careful in buying adapters, as many threads look similar. Make sure you are getting the right size and type - there are pipe threads (used here), Flare and double flare threads, fuel line threads, screw threads, and many others, and they can be very confusing to tell apart. Read the labels, and insist on seeing the bin they get the adapters out of to verify they are correct. Everything should screw together easily with very little friction, and the male part should have a slight taper to it - as it tightens itself as you screw it in further. One last thing: In pipe threads, the nominal dimension is the ID of the connected fitting - thus 1/8 pipe is actually nearly 1/2 from flat to flat on the fitting hex, probably 7/16 on most Weatherhead adapters (which is what the name on the orange cabinet the guy gets the adapters out of will say.)

All these devices use pipe thread, so you do not need to tighten anything, just finger tight is adequate for testing purposes - it might seep a little bit, but that won't affect what you are trying to read.

Others may be better informed, but I'd guess a healthy 318 would produce around 40 PSI cold idle, and I'd like to see at least 15 PSI hot idle. Your idiot light should have a threshold of 7 PSI or so, so if it was flickering with SAE 30W oil in it, your clearances are getting a little loose. At 1500 RPM or so, I'd expect maybe 50 PSI cold, or even a little higher, and perhaps 30 PSI hot, with 30W oil (which you should be using, and I don't mean 10W30 or 5W30).

This page last updated June 27, 2004.  Send us your feedback, and come join the Imperial Mailing List - Online Car Club