Overheats at Idle

[adam_knox]

Hi gang!

I have a 1949 Chrysler Windsor Convertible C-45. Its stock. Took it out the other day and if its idling it'll overheat when its 80 degrees out. If i rev the engine in neutral the temp will go down (usually runs around 180 degrees on the dash thermostat gauge).

 

I've had the car for probably 14 years and has been pretty reliable. I like to drive the car and feel confident it will get where we're going AND back! =p

 

So my question is, per this Hagerty article https://www.hagerty.com/media/maintenance-and-tech/dependable-cooling-system/  it says to replace the radiator. I was already planning on replacing the thermostat and water pump since I'm guessing they are hitting the end of their life (if they aren't the culprits to the overheating). In any case, replacing the radiator seems sort of overkill, not sure on the life span and reliability of our radiators. Anyone have experience taking them to a radiator shop and having them refurbish 'em? Just want to bullet proof as much as I can without being too wasteful or leaving the stock set up I have.

[Plymouthy Adams]

check the tension on the fan belt as when revved it seems to be cooling per your report....

[Go Fleiter]

I changed only the inner radiator mesh.

Bring the car, not only the radiator to the shop.

Maybe You have enough space for a triple tropical mesh,

which maybe will stand a little out of the frame.

It would be worth wile, because it will cool much more reliably.

I have a big additional electrical fan (off an AC system) too.

My car has no longer overheating trouble in trafic jams in summer.

The modern mesh will maybe have a different look than the old one.

  And a working thermostat is always needed, as to cold is bad too.

I never understood the choice of "desert" vs. "Alaska" thermostats as

the engine needs the same operating temperature in both regions.

Greetings from Düsseldorf!

Go

PS.: Always think of the water pump and water disribution tube, Chrysler engines have such too?

Edited June 10, 2020 by Go Fleiter

[Loren]

A good cooling system flush is a place to start.

You'd be shocked at how much muck can accumulate in there.

One thing I used to do in front of a customer was to take a volt meter and put one probe on the neck and the other in the coolant with the engine running.

I've seen as high as 12 volts generated by the motion of the coolant and the chemistry of the corrosion!  Try it.

Then think about how the iron (the brown stuff) gets in the coolant...it's dissolving the engine block.

Flushing the radiator and heater core go a long way to fixing the problem.

The honey comb cores of the original radiators are very long lived and if clean work well. I'd try my best to keep it or find another to replace a finned one.

 

Mopar engines also have a water distribution tube in the block. Its purpose is to even out the temperatures in the engine and it does a fine job of it as long as it is not plugged or corroded. If you ever have the head off, you will see how much more distance there is between the valves and the cylinder bore on a Mopar vs other flatheads. That space accommodates the water distribution tube. Its good design which promotes a long lived engine.

Then there are the usual suspects, thermostats that stick, hoses that delaminate inside and block coolant flow, slipping belts and fan blades (for many reasons).

 

Ignition timing can be too retarded and cause idle temps to go up as well.

In the 1970s one of the easy smog fixes the car makers used was to retard the ignition. They did it so much that the car would overheat at idle on hot days. They prevented that by putting a thermostatic vacuum valve in line with the vacuum advance. When it got too hot it opened and the engine got a few degrees of advance from the distributor vacuum chamber thus reducing the coolant temp.

The mechanics took about a nano second to figure out that setting the timing to the old spec and moving the vacuum line to the old place on the carburetor would yield the old performance and fuel economy.

Just a few of my thoughts on the matter.

[plymouthcranbrook]

If you have a laser thermometer you can use it to check to difference in temp from the top of the radiator to the bottom.  If not much cooler at the bottom blockage or restriction is likely.

[kencombs]

2 hours ago, adam_knox said:

Hi gang!

I have a 1949 Chrysler Windsor Convertible C-45. Its stock. Took it out the other day and if its idling it'll overheat when its 80 degrees out. If i rev the engine in neutral the temp will go down (usually runs around 180 degrees on the dash thermostat gauge).

 

I've had the car for probably 14 years and has been pretty reliable. I like to drive the car and feel confident it will get where we're going AND back! =p

 

So my question is, per this Hagerty article https://www.hagerty.com/media/maintenance-and-tech/dependable-cooling-system/  it says to replace the radiator. I was already planning on replacing the thermostat and water pump since I'm guessing they are hitting the end of their life (if they aren't the culprits to the overheating). In any case, replacing the radiator seems sort of overkill, not sure on the life span and reliability of our radiators. Anyone have experience taking them to a radiator shop and having them refurbish 'em? Just want to bullet proof as much as I can without being too wasteful or leaving the stock set up I have.

I have seen pumps with plain steel vanes/impeller do that when the vanes were mostly gone to the corrosion.  Another reason the do a cooling system flush and change coolant regularly.  Most old Mopars had cast iron impellers, but it's possible that yours has be changed to a cheaper aftermarket or rebuild some time in its' history.

[Sniper]

7 hours ago, plymouthcranbrook said:

If you have a laser thermometer you can use it to check to difference in temp from the top of the radiator to the bottom.  If not much cooler at the bottom blockage or restriction is likely.

 

I recently did that on my 51, I got a 30 degree difference between the two, as a reference.  Not sure if that is good, bad or indifferent.

[greg g]

First thing to do is verify the accuracy of the gauge. Overheating at idle usually indicates insufficient! Work flow through the radiator. The fact that it cools some wen you Rev the engine supports that.  Fan belt tight?? Core clear of debris leaves dead bugs, spider webs?  Did you check to see if one of your radiator is collapsing with heat and suction?

[adam_knox]

Thanks for the replies guys!

Checked the belt, snug as usual. 

Talked to a radiator shop, for 80 bucks they'll boil the radiator and clean it out. So while they are doing that I'll be inspecting the pump and thermostat.

 

Gonna keep my eye out for one of those laser temp things!

[adam_knox]

Well took out the radiator and the heater radiator and took it to the shop today. It was clogged up. He said everything else about the radiator at first glance looked good since the previous owner had replaced the fins, so its a bit modernized. So I get it back in a week.

 

Going to order a new thermostat, waterpump and gaskets. Was going to order it from Andy Bernbaum. Was thinking of replacing the hoses too since they are at least 12 years old and quite firm around the metal ports they were attached to. Better to get that from a local part store? Just want to get new rubber rather than something thats been sitting on a shelf for awhile drying out.

 

When I'm flushing out the engine with a hose, should I go ahead and take off the water inlet ports/tubes by the exhaust manifold too? Was thinking about replacing my exhaust manifold gasket and gasket that goes to the exhaust pipe anyway as I have a rattling sound when I first go to accelerate in 2nd gear and I think it might be an exhaust leak (but that's for another thread!).

 

 

[plymouthcranbrook]

NAPA had a good reliable pump when I need one although that was about 15 years ago. Bought the other parts I needed for cooling system there as well.

[49WINDS]

@adam_knox - just curious if you had put everything back together yet and if so, have you had any luck in fixing your overheating problems?

 

I too have a '49 Windsor, although it's a 4 door and not a convertible, so I imagine most everything is the same between our cars. I have only had mine since April but shortly after getting it I flushed the cooling system the best I could without taking everything apart. While it runs nice and cool when I'm driving around, I have the same problem as you with anytime I'm stopped for too long. It happens mostly in drive-throughs but also if I'm sitting at a long red light I'll see the temp gauge begin to creep up and go over 200. I know I got a lot of sediment out of the block when I flushed it, I actually had to unscrew the entire drain plug assembly on the block and poke a screwdriver in there to loosen up all the crud before it would even drain. Since it will cool back down if I rev the engine some I had thought that maybe I just needed to install a 6 blade fan instead of the 4 that's on there. But now I'm wondering if I need to take it further apart like you did or maybe even pull out the water distribution tube.

 

I'm eager to hear your results!

[wagoneer]

I recently fixed my overheating issue with a new water pump, thermostat, and hoses. I'll look into having my radiator boiled next time. The pump and thermostat solved my problems. I used a set of hoses from Berbaum's that were good but needed a bit of trimming. The stock clamps are cool, and give a nice accent visually to the engine.

[captden29]

I once tried the 6 blade fan and it actually made the problem worse. I think it is a universal fan, but I did have to have the center hole enlarged at a machine shop. don't forget the water distribution tube. good luck. keep us posted.    dennis

[Dodgeb4ya]

The core plugs must be removed to properly clean out the engine block cooling passages.

The radiator should be checked out by a qualified radiator shop if one is available. Not many left anymore sadly.

Honeycomb radiators are extremely difficult to bring back to OE flow specs and repair leaks....

This leads to a tube and fin recore or new import aluminum radiator..

[Sniper]

I washed the Cambridge last week and while I was there I made a point of cleaning the fins, lots of real fine clingy dust around here.  It appears to have made a noticeable difference in my running temps.  It's cheap and it may work for you.  I was at one of those coin op car wash places and use the high pressure wand.

[kencombs]

40 minutes ago, Sniper said:

I washed the Cambridge last week and while I was there I made a point of cleaning the fins, lots of real fine clingy dust around here.  It appears to have made a noticeable difference in my running temps.  It's cheap and it may work for you.  I was at one of those coin op car wash places and use the high pressure wand.

 

Excellent point.  I've been into old garden tractors, well small tractors in general for a long time.  Small diesels from Kubota, Yanmar, JD are really sensitive to that.  My little JD 455 with a Yanmar diesel will mow all day long in 95+ temps with no problem, IF the radiator is spotlessly clean on the outside.  Let a film of dust accumulate, which happens quickly in hot dry weather when mowing,  and it will overheat.  Clean the screen and fins and it's fine. 

 

And the honeycomb radiators on old Mopars seem to be more vulnerable to  this that the more open designs.  Better at heat transfer, but the design does trap 'stuff'

 

BTW, if you haven't seen this video,  https://www.youtube.com/watch?v=Cxt6EN-39Ck

it's really interesting.  I had no idea that honeycomb cores were still being made.

[Sniper]

To Ken's point, I am still running the original honeycomb radiator.  So this is something we all ought to keep in mind.

[Los_Control]

Interesting video. My truck idles cool with original honeycomb. I did flush it both ways and seems to be clear.

Sadly it has about 5 holes in the tubes, just drips at idle, goose the throttle and get a shower   

I bought a aluminum radiator I plan to paint black but not installed it yet.

[Blue Goose]

My 1947 P15 Special DeLux just started to overheat. It stays in a heated garage most of the time. I only drive it 150 miles per yr. I had the engine rebuild about 6 yrs ago. Still using the original radiator with new water pump and thermostat. Not sure of the cause yet. I am going to try a radiator flush with Simple Green detergent and water (youtube). Not sure it this is safe on a copper / brass radiator. Any precautions out there.

Tx  BlueGoose47

[Sniper]

When ever you want to know a chemical's potential to react to something look up the SDS.  I did this for the original Simple Green for you and it is listed as non-reactive.  Which means it should have no effect on brass or aluminum.  https://simplegreen.com/data-sheets/

 

Though there is some that comment on it's effect f you soak it for a long time, like weeks and months.

 

If that worries you Simple Green makes an Aircraft and Precision Cleaner that is supposed to be safe on aluminum regardless. 

 

https://simplegreen.com/faqs/#

 

Click on aluminum in the FAQ. 

[Tooljunkie]

8 hours ago, Blue Goose said:

My 1947 P15 Special DeLux just started to overheat. It stays in a heated garage most of the time. I only drive it 150 miles per yr. I had the engine rebuild about 6 yrs ago. Still using the original radiator with new water pump and thermostat. Not sure of the cause yet. I am going to try a radiator flush with Simple Green detergent and water (youtube). Not sure it this is safe on a copper / brass radiator. Any precautions out there.

Tx  BlueGoose47

Had a transmission cooler fail inside the rad in a caravan, polluted the cooling sysem. I flushed it with simple green. When i pulled housing to replace thermostat, inside of intake manifold was gleaming! Checking after filling with coolant, there was no evidence of any oil in the cooling system. Very impressed with how well it worked. And that van had the best heat of any vehicle i have ever owned. 

[Blue Goose]

Thank for the info guys. 

[Blue Goose]

Status and question

I have flushed the radiator with a diluted Simple Green and distilled water solution. I ran the engine for about 5 min. The block was getting hot and the large hose was remained cold. 

I have since rinsed the radiator core with more distilled water and will drain again. Waste water was pretty clean. No large about of dirt or metal (none). 

Question

How can you tell if the over heating is thermostat or water pump? This is a relatively new water pump with very few miles on it. Replace when engine was rebuilt 6 years ago.

[Sniper]

It takes more than 5 minutes of idling to get the thermostat to open up in my experience.  An IR gun will tell you what's going on.