Cleaning and Flushing Your Imperial's Engine Block


Imperial Homepage -> Repair -> Engine -> Flushing

Tip from Ross:

There are no guarantees on trying to resurrect an improperly stored engine; the following is what worked for me:

Yes, you can use tranny fluid. You'd be best off, though, by pulling and cleaning the oil pan and oil pump pickup and screen, checking rod and main bearings for clearance and condition (not expensive to replace at this point, but if engine is otherwise no good, then money's gone).

NOTE: You're gonna have acid etching in the bores and on the bearings, and rust and varnish in the engine. It can't be avoided if it was just parked and not run . . the only question is how well the engine runs afterwards.  Compression will be off overall - even badly in one cylinder or another - the
valve-springs are gonna be weakened, stem seals are probably goners if original, etc. This doesn't mean it won't run, it probably will, but it'll take some work. And if you know the cars history of oil changes, then all the better.

If you don't, pull the intake manifold and examine the lifter valley for sludge. Pull the valve covers and examine for same; also to check for loosened pushrods.

Disconnect the battery and the coil, then pull the distributor (be sure you mark the direction of the rotor for reinstallation), look inside engine block to see if the shaft bushing hasn't pulled loose (they do, and timing is thereafter erratic and/or the distributor shaft can break if bushing not set; make a scratch mark on the rotor and bushing to realign later). Pull the spark plugs, squirt some WD-40 at the highest piston edge - let it set awhile - then squirt some machine oil or motor oil same way, get an oil pump drive tool you can s-l-o-w-l-y (75-150 rpm at first), using an electric drill, turn the pump with after you have filled crankcase and filter (about half full, you're gonna spill some reinstalling it) with your favorite concoction. I also connect an oil pressure gauge at the sender for the idiot light (or whatever your car has) to monitor pressure rise.

I like tranny fluid because it ain't too strong (compared to a butyl cellosolve flush), has very high detergency, and mixes pretty well with dirt-cheap 10w or 30w. After bringing pressure up to normal, continue for several minutes. Then, set car back up for running, drain that crap out, add more cheap oil with another filter (check behind filter spin-on for crud), install new plugs, new fuel filter (and you might go thru 3 or 4 of these if tank not pulled and boiled) (plus it won't hurt to overhaul that carburetor, it'll need it), check wiring, check ALL fluid levels, install new battery and see if she'll fire. If not determine the nature of the problem and correct.

Once running, idle her at 1200-1500 for about 20 minutes or longer, until it is fully warmed up. Drain out the garbage (I usually let her sit overnight or at least an hour with the drain-plug out); refill, add new filter and drive about 250 miles in a day or two; repeat long drain and refill with synthetic
using a synthetic media filter (Mobil One for both); drive it a few hundred or a few thousand miles checking oil color very regularly, and, when fully darkened, change yet again. I use STP Motor Flush on any car having gone through the above about every 18-24 months until oil no longer significantly darkens between changes (6,000 miles or 4-6 months). On a car rarely driven (1000-2000 annually), just change it at least annually. Have resurrected several long-undriven cars this way.

Question from Dave:

Here is a curiosity I haven't before encountered. In the overflow bottle of my 1973 Imperial, there is a large amount of sludge clinging to the overflow tube and the sides of the bucket. The sludge has a light brown, crumbly appearance, is slippery to the touch like wet clay, and has no grit. What could it be? I suspect this substance may be a symptom or cause of my Imperial's running a little hot lately (no boil over or burst hoses, however). Any suggestions for radiator/cooling system flush products? Of course, I will remove my AutoTemp II servo before flushing.


From Bob:

I've cleaned out several overflow bottles in the last few years and found "glop" in all of them. Who knows what it is? Who cares? It cleaned up OK. When I flushed out my Imp's system 2 years ago, I used a Prestone flush product. Put it in, run the car a while, drain the water. Repeat. Repeat! The system was draining fairly clean. I filled it with the new formula coolant, Havoline Dex-Cool. It's supposed to be more corrosion resistant and "long-life". The car has been running cool ever since, knock on wood...

From Chris:

I have found this gray sludge every time I've either re-cored a radiator or flushed the cooling system of an older or long-dormant car. I suspect that it is the accumulation of the deposits from throughout the cooling system, especially the engine block, that suddenly come into the overflow bottle when clean new coolant is introduced and the system runs a little freer. I find that a thorough engine and cooling system flush, sometimes again after another 500 miles, removes most of the sludge. 

Question from David:

I removed my valve covers today, to replace a leaking valve cover gasket, and found the entire inside of the valve covers (and rocker arms, valve springs, push rods, top surface of heads...) covered in a thick crusty black gunk. I just bought the car, and am still in the process of registration, and titling, so the only times I've actually driven her were: a short test drive before I bought her, and off the trailer into my driveway, when the guy delivered her. The engine ran smooth and strong both times. Common sense would tell me that it's 35 years worth of oil splattered around in there then caked, and charred with the heat of the engine. The problem is I've never seen anything like this (at least not this extreme), when pulling valve covers off any of my other cars. I'm in the process of cleaning the covers, and plan to clean the top end of my heads, before replacing the covers. I'm worried though, that this same buildup could be throughout the motor's oil passages, and can only imagine the damage this could cause down the road. I'm curious if anyone knows what might cause it to be this extreme( 1/8"-1/4" thick coating every surface under the valve covers), whether or not I should be concerned about the inner workings of the engine, an if there's any way to remove this buildup from the inner oil passages short of pulling the engine apart, and rebuilding it. Are there any oil additives, or other means by which to flush out any crud that might be clogging my engines arteries?


From Kne:

This used to be more common with non-detergent oils, but it is usually a result of infrequent oil changes and a hot running engine, or an engine that has overheated periodically with in- frequent (or none) oil changes. Again, non detergent oil aggravates the situation. I would also say that the crud, unfortunately, is probably throughout most of the rest of the engine. I hope someone else can add more to this, but here are my thoughts. Pull the rocker arms and clean them and the shafts and the valve covers for sure, and of course you know you are in for frequent oil changes now if you use engine "as is". I have had more than a few daily-drivers, picked up for cheap, in this condition, so I just drove them "as is", and didn't have any problems. The crud, of course, does not effect the performance of the engine. The old wives tale, when this was more common, was not to switch to detergent oil, as that would break the crud loose and cause problems. Makes sense, but I never tried it. What I personally would do, because I pull engines often and I'm set up to do that, if it's a good running engine and does not need rebuilding, I'd pull it, put it on the engine stand, strip it down to the short-block, and then just start scraping and cleaning with rags, gas, screw-drivers and scrapers. If you leave it as-is, I guess the big fear is that a chunk breaks loose and plugs an oil passage. I don't think chunks falling into the pan are a big problem, as there is a screen on the pick up, so that actual chunks are not going to go through the pump. When you have the rocker arm shafts off, take a good bright pen-light and look down the passage that feeds oil to the shaft. That should give you an idea as to whether the passages are anything like the inside surfaces of the engine. My gut-feeling is that the passages may be o.k., and most of the crud is on the inside surfaces where the oil was not moving so fast, and had time to bake on. (no PCV also aggravates this problem) If the passage looks o.k., I would leave the engine alone for a while, change oil and filter often. It would be really good to find out what kind of oil was being used in it before you got it. It might still be on non-detergent, if so, you might want to stick with that if the "old-wives" tales are true. I'd be surprised though, most people are not aware of detergent/non-detergent oils, and just have the mini-lube put in their 10-40. So it's probably running on detergent oil now anyhow. If you feel real brave, give the engine a couple of treatments with oil-flush, change oil every 500 miles for a time and see what happens. Again, if the oil passages are not actually plugged, I don't think you will be in danger of losing oil pressure, the problem will be a large amount of abrasive material going through the oil pump, some passing through the filter. Get the best filters you can, change oil as often as it get black looking, even if it's only a couple of hundred miles. Oil pump is not hard to change on the big block, so I would not worry too much about trashing it. Be sure to use a straight grade oil of reasonable weight, 30wt, while all this is going on. My Mopars all like Castrol 30wt. (actually I'm using Mobil 1 a lot, but I don't think you want to do a Mobil 1 oil change every couple of hundred miles!!!) ($$$$)

From Uncle Pete:

I have run into that situation on a V6 GM (wife's Olds Ciera). When we bought the car (used w/86K), it ran good. After a couple years, I replaced the valve cover gaskets. When I removed them, the crud was SO thick I literally could NOT see the valve springs. I mean, there was OVER 1" of crud everywhere. I simply could not believe it was still running. We nicknamed it "Sludgy the Whale". Soon after that, it developed a rod knock, so I replaced the engine. When I disassembled the old engine, the lifter galley was literally bridged with to bank.. I don't think the oil was EVER replaced for the original 86K. I have used Mobil One since. Now with another 80K, the heads still look new. You might want to try one of those engine flush treatments (Rislone), but it may take several treatments to dissolve just some of that sludge. Of course, scrape and remove as much of it as you can from the heads before you continue.

From Dick:

I would not try any kind of detergent booster or "motor flush" stuff because you are likely to let loose more crud than your oil filter can handle. The crud that is stuck on tight is not on parts that have to run in contact with other parts, and it will not do any more damage than has already occurred unless it breaks loose and begins to circulate with the oil. My advice is to clean up what you can get at easily, and leave the rest alone until you decide to rebuild the engine, then have it hot tanked or better yet take the bare block to a metal "laundry" place and have it stripped all the way down to the casting. The engine will possibly continue to run just fine the way it is. The cause would most likely be a failure of the PCV system, possibly compounded by the way the car was driven (many short trips) and/or by using very cheap oil and long to never change intervals.

Question from David:

I plan to remove the radiator and heater core and send them to the shop.   Then I plan to remove the plugs like you said and clean the cooling system by hand.  At that point what do I do, run water through the system with a water hose?  

Reply from Dick:

Basically, you'll find an incredible accumulation of slop, glop, mud and crud in there, and you have to use anything you can get in there to scoop it all out, or as much as you can get out. 

When you are all done, and thoroughly dirty yourself, flush with water, and, if you have it, an air hose, to blow the stuff out that you couldn't reach. I find a hacksaw blade and an ice pick to be good tools for this. 

I've forgotten what year your car is, but if it has a 440 or a 413, you'll find 3 core plugs on each side of the block. You can get at the passenger side rear plug fairly easily, so pop that one out first. If everything looks quite clean in there, with no more than 1/4 inch of mud on the bottom of the water jacket, I wouldn't bother with the rest of them. The rear plug is always the worst. If there is a significant build up of mud in there, you'd best pop all 6 of them out. 

To get to the rear one on the driver's side, you have to remover the starter. To get the front ones on each side, you'll have to be a contortionist to get at them, because you have to work in very narrow clearance because of the motor mounts. You can make it easy by putting a large block of wood to a jack under the pan to support the engine while you remove the motor mounts, or you can work through the small clearance behind them. I do the latter, out of laziness, but you decide. 

When you begin the process, you'll find two drain plugs in the block, just to the rear of the center core plug. These may be brass, so use a very good fitting 6 point socket on them, to avoid ruining them. You'll probably find nothing comes out when you pull the plug, because the mud is blocking the hole. Push a small screwdriver in the hole and then jump back, because you are going to get a bath in sludge!  

This page last updated October 15, 2001.  Send us your feedback, and come join the Imperial Mailing List - Online Car Club