Conventional Heater Repair Information for Your Imperial

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Question from Rex (1959):

Here's a question regarding the heater in my '59. Having replaced the core this summer I was expected to be toasty all winter in my Crown, but now the following is happening: When I first start out in the morning, the heater works great, but when I hit the freeway, it grows colder and colder until I stop again, then it warms up. If I stop completely for a few minutes, it sometimes works fine the rest of the day, then again it works until I hit a high speed.

Is the heater valve the culprit? That's all I can think of--sluggish flow or something? Are these obtainable without difficulty if that's the prob? I'll appreciate any opinions as I have never had anything like this happen before.


From Mike:

Could you possibly have some trapped air in the system? Try removing one of the heater hoses and listen for a gurgle. Then also unloosen your radiator cap to the first detent, without removing it. It should be loose enough for air to escape but not be able to be pulled off. Next start your motor and let it warm uip. Keep an eye on temp guage and as temperature increases, rev engine a couple of times every 5 minutes or so , but just rev to about 1000 rpm for a couple of seconds at a time, to ensure that thermostat is opening up. Let engine idle for 15 to 20 minutes, then shut off. Wait about 10 minutes to see if any coolant rises up and out of radiator or whether you can hear any gurgling. Repeat the above a second time. Do all of the above with your heater valve wide open to extreme heat. Hopefully this may solve your problem.

From Steve:

Could be the vacuum going to the heater valve. Try to run direct vacuum to the valve and see if that helps.

From Julian:

You may have a bad waterpump. Check it and see; also check the belts to see if they are loose.

Question from Bill (1959):

While out test driving my Imperial today I noticed smoke coming in the car from under the dash board, and up through the vent onto the windshield, and also out of the outside vents by the wipers. I have seen this happen before, after the car had not been driven for a while, and figured it's just stuff burning off the block and exhaust and coming through the firewall. Today however it was prolonged, and even started to cloud up the windshield. I pulled over and looked under the dash, and then in the engine compartment, but could find nothing. It must be in the area of the outside vent between the firewall. Any ideas what this might be? The only thing that I could figure is maybe the heater unit.


From Phil:

Uh oh, it sounds like your heater core has given up the ghost. Coolant won't evaporate from the windshield like regular water vapor and can be a real pain when driving. You may want to check for a coolant-antifreeze smell. Keep an eye on your coolant level in the radiator and for wet floors under your heater unit! And if anyone has a good source for heater cores, now would probably be a good time to speak up!

From Bill:

If it's a white vapor and coming out of the defrost openings, it is probably a bad heater core. If it is a burning smell you better check your wiring.

From Dick:

You have a bad heater core, the vapor is coming out the defroster vents and condensing on the cold glass. Disconnect and block off the hoses to your heater system until you get a chance to have the heater recored.

Any radiator shop can put a new core in your heater, but he needs the old core to swap the end tanks and fittings. Just block off the hoses, take out the old core, and take it to a radiator shop. It will cost under $100.

From Neal:

I had my heater core removed by a local readiator shop in summer 2001. They sent it out for a rebuild by Old Air Products in Fort Worth. Their web site is; 4615 Martin St., Fort Worth, TX 76119;
817/531-2665. It took about 2 or 3 weeks, I think, and the price was fairly reasonable, though I don't remember how much. The heater core was dribbling on the floorboard, so I had it done before it got worse. It's been fine since.

From Bob:

You may want to check the passenger side floor just under the dash. My experience on leaking heater cores always swamped the carpet and if left in that condition too long, well you know what happens. Look up the part number for the core , it may be a common one for Chryslers if your lucky. Then when you take the old one out, you can put the new one back in and be done with the problem.

Question from John (1963):

I need some help figuring out how the heater is supposed to be plumbed in the 63. Evidently the control valve failed and the heater is now directly connected, making for very uncomfortable summer driving. I am going to get the control valve rebuilt/replaced, but there is another vacuum actuated valve mounted on the passenger fender that I don't see in the FSM. Is this supposed to be there? It looks like the hose may have connected through this valve before it went to the control valve on the fire wall.

Reply from John:

The hose should go from the water pump to the control valve & out the other side of the control valve to the heater. That other item sounds like an add on.

Question from Bobby (1964):

While pulling the evaporator off of my "new" 1964 Crown, a leak was discovered in the heater core. Which is the better fix; find a new core or send this one to a radiator shop to be fixed for about $30.00?

Reply from Steve:

New core or recore. Old core will just leak again later.

Question from Chris (1965):

I was thinking of bypassing the heater core in my 1965 Crown during these HOT summer months. When I'm driving around it feels like the heater is on all the time (but of course it isn't). The heat just seems to radiate from under the dash (but no air is blowing in). I would just like to reduce the temperature in the passenger compartment to tolerable levels.


Does bypassing the heater core cause any long term damage? I definitely want the heater to work during the COLD winter months...


From Joe:

I have an inline cut off valve in both my 81 IMP and 76 NYB.

From Steve:

In the HELP section of most parts stores you will find some little plastic caps for this purpose. Remove the heater hoses and insert the caps then clamp them down. Works like a charm and should not cause you any mechanical problems at all.

Question from Chris (1965):

I managed to successfully bypass the heater core on my 65 Crown (for the HOT California summer). It made an immediate difference in the cabin temperature.

Also, I noticed that when I engage the "AIR" button (this is not an A/C car) on the control panel I get (surprise) cool, outside air. Before the bypass I would also receive HOT air through the defrost vents; this air is now cool as well. I like this VERY much.

My question is this:

Do I run the risk of damaging my now-bypassed heater core by running the AIR (vent) system? I definitely want my heater to still work when I reconnect it this winter...

Reply From Johan:

I bypassed my core this summer and plugged everything up with a good rubber seal (plugs) to keep the air out and coolant in the core, to detour corrosion.

I'm also replacing the valve because it leaks slightly while I do this. It shouldn't be detrimental as long as eventually (this winter perhaps) the flow of coolant returns.

Question from Dave (1965):

I have a problem with my heater system. I discovered coolant leaking onto the passenger floor. I pulled the heater core out and bench tested it. Low and behold the heater core doesn't leak. My next guess is the heater control valve. Do I have to take the dash apart to replace it??? Or can I hook-up the heater core without the control valve??? Will the A/C work( when I get it fixed) ok with just the heater core hooked up??


From Chris:

Sounds like your heater control valve is leaking. To remove it you only have to unscrew the valve from under the hood, remove the copper thermostatic wire assembly from the heater core box (it is attached the control valve also). Inside the car, remove the glove box liner, reach in and pull the valve and thermostat towards you. Detach the control cable. And don't lose the cable retaining clip - it is not always included with replacement valves!

Until you find a heater control valve you could either disconnect the heater core (looping the heater hose back to the water pump) or install an inline spigot that you turn on & off manually. Either way your A/C will work fine without having to overcome a warm heater core. (Note: incoming air is cooled first, then passes over the heater core and is reheated, so any hot coolant seeping into the core will defeat your A/C.)

But take action soon. Hot coolant can permanently discolor your carpet.

From John:

That is the control valve leaking, a very common problem. To replace, you need to remove the glove box, everything else should be accessible. You can bypass the valve, the only problem is that you have full heat going through the core & even with the fan off, will make it warmer in the car & if you have a/c, it won't get very cold. To bypass, make sure to release pressure at the radiator first & retighten the radiator cap. By keeping the radiator cap on, it should help reduce the amount of coolant coming out when you disconnect the hoses. Remove the short hose from the heater that is running from the control valve & replace with the long hose that is connected at the heater valve. Run the engine with the radiator cap off for a few minutes to allow trapped air to escape & top off coolant it needed. 

Follow-up question from Dave:

I got out the heater valve after removing the glove box, only about 15 minutes. As predicated, the heat valve is the culprit. It is leaking where the little rubber piston moves in and out of the pipe. So off I went to NAPA, hoping that someone still makes it. So much for luck !!! It is Ranco type H16. The guy at NAPA said I could used a cable operated valve as this valve is also cable operated too. So my question is does any one have a used one or even NOS one??? Who should I call to find one ???

Reply from John:

J. C. Auto sells these.  This is the same person that does the Electroluminescent dash repairs & the heater valves are his other specialty.

Reply from Bill:

You can send yours to be rebuilt and the guy does a good job. Cost is around $75 and well worth it, as I know friends who tried to adapt other control valves and they wound up with a Mickey mouse set up. Contact: A. Petrik Phone 425-255-4852

Reply from Neal:

I had the identical problem with my non-air conditioned '59. The radiator shop sent the control valve to Old Air Products in Fort Worth.  They claim a 4 day turn-around to rebuild.

Question from Ken (1966):

On my ' 66 Imperial my I am leaking antifreeze in my passenger floorboard. I changed what appears to be the front heater core. Are there two heater cores? One for the front air and one for the rear air set up?


From John:


Check the temperature control valve for leaks.

From Jay:


Don't rule out the Heater Control Valve (HCV) as the culprit. I pulled the heater core and had it pressure tested to 30 psi and no leaks. Only then I knew that the leak was the HCV. If the '66 uses the same as the '62.   It's a Ranco H-16, and there are several sources that rebuild them.


From Dave:


If the '66 has the same rear heat setup as a '67, yes you have a heater core, blower and ductwork in the trunk beside the spare tire and it ducts in between where the back seat bottom and floor meet. It is fed by heater hoses coming from the heater control valve that controls fluid flow for the front heater.

Question from Matt (1966):

Awoke the '66 from the garage today as the wife's van has to have a new windshield tomorrow and I will have to drive the '66. I turned the heater on after the engine warmed and noticed on low speed a slight clicking noise. Can these be oiled or is something showing signs of wearing out?


From Kerry:

If the clicking changes speeds with the fan speed, you probably have a leaf or something tickling the squirrel cage fan. If that's it, you can pull the fan out or just live with it. Sometimes they go away after a few hours/days/weeks/months...

From Dick:

Most likely, you have a leaf or some other foreign object in your squirrel cage. Just take the blower motor out and inspect it.

These are getting hard to find new, but there are close enough equivalents you can use, with a little rewiring. If you conclude that it is the motor itself, (which I doubt), take it to your NAPA store and use their buyer's guide to find the closest equivalent. I seem to recall one from a Peterbilt truck is almost identical, but you have to rewire the harness to it.

Question from Jerry (1970):

I have a 1970 Imperial with Automatic Climate Control. Here is the problem. The heater motor does not respond properly. If I activate the defrost, it appears to work. When I switch to auto heat / cold the heater motor will run at high speed. The AC works for several minutes and then quits. If I go back to defrost, wait for the motor to start again, I can than go back to AC for a short time. If I jumper the motor, all functions appear to be working. A test light indicates that the motor in not getting any power. The manual states the resister block might be bad. I cannot find this part. Any ideas? If I find it, how do I test it.


From John:

I'm pretty certain that the resistor is the same on the '70 as the '69. Is up a ways under the dash at about center, If it is bad, the coils will probably be burned & melted. Another possible culprit is a vacuum leak.

From Pete:

Having had a '70 LeBaron (for 20 years this month!) I can safely say that I know the source of at least SOME of your cars problem.

The vacuum check valves located on the underside of the heater core/evaporator case have failed. When the valves won't hold vacuum,
the blower turn-on vacuum switch isn't activated.

These are plastic bodies valves with 4 ports each, p/n 2820 880. They are used on quite a few cars from the mid-60s up into the late 70s and
they all have the same problem -- an internal chamber cracks. This is because a plastic cap is pressed into the chamber and long term stress
causes the chamber to split. Here's a pic:

(Click on the image for a larger size.)

I've used Parts Voice and other locating services to search for these and they are out there.... At $20 -$40 each. The problem is that I
believe ALL these valves will have the same problem regardless of whether they're NOS valves sitting on a shelf or "used" parts in a
junkyard car. I couldn't get any sellers to check the valves (simple test with a short length of hose and a vacuum pump) so I didn't buy any.
$40 for a very likely broken, not returnable chunk of plastic was too much of a gamble for me.

I've been searching for an alternative for the valves and even finding a way to repair them using my lathe but that hasn't happened yet.

Question from Kevin (1971):

I noticed antifreeze coming out the bottom of my heater, and its all on the floor mat. In the mornings my window does not defrost, it fogs up really bad with the defrosters on. Is my heater core going out?  if it is is it hard to fix?


From Dave:

I have never worked on your model before but the heater core is shot and needs to be replaced. If you don't have a shop manual for your car check the local library, they normally carry MOTOR or Chilton's repair books and you can just check it out instead of buying one.

From Wayne:

You definitely need a new heater core (been there, done that). It is not hard to replace, and a good radiator shop will be able to make up a new one for you.

From Bill:

It may also be the heater control valve. Check that as well. You can bypass it if you need to for now, if you don't have the money to fix it. I have done that on each of my cars until I was able to get a rebuilt one from Jeff Carter here in Seattle.

From Bill W:

Heater cores can be removed from the car and taken to a radiator shop to be re-cored. You will need to check a shop manual or a manual from Chilton's or Motor for instructions on how to do it. I have never removed a heater core on an A/C equipped C body before - did a 1972 Polara Custom in 1986, though. (If you are working on an A-body or 1960's Studebaker, I could write up the directions from memory, done it so often.)

By the way, if you want to know what color your antifreeze is, next time your windshield fogs up with the defroster, wipe the windshield with a clean, white paper towel. That "fog" is actually antifreeze from your leaking heater core.

And do not use any stop-leak product. It will stop the leak. temporarily, but it will also gum up your cooling system in other places as well. The only cure for your problem is fix that heater core.

From John:

This sounds more like the heater core, since the windows are fogging. I believe the control valve only allows the coolant to leak onto the floor. Also, I don't think they had the control valve problem after '66.

Question from Leo (1983):

Lately, My heater has been screwing up. Several times lately, it warms up just fine, then all of a sudden, the warm goes away and it blows cool air. No amount of adjusting the Temp. contol lever will solve the problem. I believe it is the "Semi-automatic" heater system. I have checked the coolant level and it is OK, The thermostat and Rad. cap were new two years ago. Any ideas?

Reply from Stan:

Check your control unit on the heater is a vacuum contoled unit on the line into the heater core.

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