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'41 Chrysler Straight 8 Overheating Question


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I have a 1941 Chrysler Saratoga with an inline 8 engine. Car drives fine, and does not overheat while driving, but noticed lately that the temperature gauge goes into the red if left idling for more than 5 minutes, stalls out and will not start again until the temperature gauge goes down a few notches. Once driving, there are no overheating issues.

Today, took the car for a drive, ran nice and cool, but after turning off the engine, the temperature gauge rose into the red again. Is this common with these engines? I'm still getting to know this car, and not entirely familiar with some of the idiosyncrasies of these C-30s. Any ideas or suggestions?

Thanks!

Dave

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Sounds like the cooling system is marginal. Is the matrix clean on the outside, not full of bugs and dirt? Can be cleaned by vacuuming from the front or blowing with compressed air from the back.

Could also be full of scale on the inside. Might help to flush the cooling system.

You can do this by draining the coolant, filling with plain water and a couple of bottles of CLR calcium, lime and rust remover. This will not damage your cooling system but could open up leaks that have been plugged by dirt and corrosion.

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Thanks Rusty, that's a good idea about blowing out any dirt with the compressor. I was planning on flushing the cooling system this week, and changing the hoses as well. The thing that I don't quite understand is why the temperature gauge would go up after the engine is shut off. I may have just noticed this issue because the weather has been abnormally cold in the Northeast until this past week, and the engine is not cooling down as quickly as it was in the cold. I've never seen a car that's done this before.

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The radiator, block and water distribution tube could be plugged up with sludge. To flush the block properly you need to remove the lower engine soft/core plugs to get all the sludge out before flushing the radiator.

The D-tube requires water pump removal to look into it to see if it is plugged or rusted out.

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Edited by c49er (see edit history)
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Called "heat soak". When you turn off the key the guts of the engine are hot but the cooling system shuts down (no more fan or water pump). So the heat gauge sensor actually gets hotter even though the engine is stopped. After a few minutes the heat starts to disperse.

Not a problem under normal conditions. In very hot weather the excess heat buildup can cause a vapor lock. if the engine will not start right away when hot, it can help to hold the gas pedal to the floor until it catches.

If the engine gets very hot it can help to pull over and sit in neutral with the engine at a fast idle. This helps cool it down faster than if it is stopped.

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If the water distribution tube rusts out, all the cooling water streams up the front of the engine and the back of the engine runs hot. This can easily be detected with an infrared thermal detector. The front and back of the engine should be the same, within 10 or 20 degrees.

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That describes the problem perfectly, Rusty. Do you know if this issue is common to straight 8's? I imagine that the overheating could be pretty rough on electrical components. I've only owned this car for about 6 months, and most of the winter it was in the garage. I've only started to work on her in the past few weeks, and most of that was spent fixing the brakes, repairing the shift linkages, and rebuilding the carburetor.

Is there anything, aside from flushing the cooling system, that helps keep this from happening?

Appreciate all the responses.

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Thanks Rusty, that's a good idea about blowing out any dirt with the compressor. I was planning on flushing the cooling system this week, and changing the hoses as well. The thing that I don't quite understand is why the temperature gauge would go up after the engine is shut off. I may have just noticed this issue because the weather has been abnormally cold in the Northeast until this past week, and the engine is not cooling down as quickly as it was in the cold. I've never seen a car that's done this before.

All good and logical suggestions above, our experiences down here are that the straight 8 has marginal cooling at the best of times.

Certainly the internal cooling tube that runs along the valve seats is a weak point in the Chrysler engine design, if you don't know the history of the engine this would be high on my priority list, however do the easy things first, rad. flush etc.

Having said all that,before I touched anything I would do as Rusty suggests and spend $30 / $40 on a hand held infra red tool to check temps around the engine / rad. and verify that the temp gage agrees with the infra red device. With a bit of dexterity you could probably put the beam on the exhaust valve locations and see if some are hotter than others, usually a good indicator that the previously mentioned cooling tube is shot.

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This is great information, I really appreciate all the responses. c49er, thanks for adding those pictures - extremely helpful!

Any recommendations on a brand of infrared thermal detector to purchase?

Just did a quick search for detectors on a popular website and saw half a dozen in the $30 - $40 range which would do the job; doesn't need to be too sophisticated for this task.

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As long as the front and back of the block are close to the same temp you are ok. If the front is, lets say 160 and the back 200 oh! oh! you have a problem. If the front is 160 and the back is 170 or 180 it should be ok.

I have not done this myself so would appreciate some feedback from some of you, who have straight six or straight eight engines and a thermal detector. I don't know exactly how much difference is normal on a good running engine, maybe no difference? Or a small difference?

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  • 4 weeks later...

Was getting my starter rebuilt, so the car was sitting for a few weeks, but I wanted to circle back around to this topic.

I got an infrared thermal detector and checked back and front of the engine block while running. While the readings were pretty close in range (192 front, 195 back) that seems to be pretty warm. Should this straight 8 be running at 180 degrees?

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Was getting my starter rebuilt, so the car was sitting for a few weeks, but I wanted to circle back around to this topic.

I got an infrared thermal detector and checked back and front of the engine block while running. While the readings were pretty close in range (192 front, 195 back) that seems to be pretty warm. Should this straight 8 be running at 180 degrees?

You might get a bang out of this guy's experience. Original owner of a 1951 DeSoto Suburban 8 passenger sedan with the original flathead six.

http://www.allpar.com/cars/desoto/suburban-1951.html

Take note of him driving this 5000 pound whale through Death Valley, in the summer, towing a house trailer.Then off to the Rocky Mountains and how smooth it is at 70MPH @ 5000 feet. And how he made it run as cool as a cucumber.

If you have a 180 thermostat it will always be hotter than that once warmed up. Your original non pressurized cooling system will boil at 212 if it is full of water (higher if you use antifreeze).

A 180 should only be used in winter, put in a 160 for summer. This was standard practice back when your car was new.

There is nothing wrong with your water distribution tube if the difference in temp is only 3 degrees front to back. In fact it sounds like there is nothing wrong at all, except too hot a thermostat. It wouldn't hurt to flush the cooling system.

Edited by Rusty_OToole (see edit history)
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Thanks for sharing that article. Very informative. Most of the time, the fix is easy. Its diag the problem. Had a over heat on a Cad. One was a calaps exhaust y pipe and another one was a torque converter. Then we had one that the lower rad hose was collapsing going down the road. These problems not really easy to diag to a back yarder.

Use to have 4 full service gas-repair stations with 40 mechanics in Det. Seen a lot from working on cars and heavy equipment since 58 when I has helping my dad at 6 years old.

4 things that is hard to diag unless its really obvious:

Overheat

Vibrations

Drivability

Electrical

Next in line

wind and air noise

water leaks

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Thanks Dave and Rusty. That was a great article. Imagine having the same automobile as part of the family for over 60 years - amazing!

The radiator was just over 180 degrees. I suspect because the car has always lived in the Northeast, and probably driven in the winter alot, the warmer thermostat was installed. I'll be driving this more in the summer/fall months, so a 160 degree thermostat would make sense. When I took these readings yesterday, it was one of the warmest days we've had this year (mid-80's). I'm going to be flushing the cooling system, changing out hoses and thermostat as my next project.

Thanks again for the help.

Dave

Quick follow up, I took the car out for a drive this morning, in sub-70 degree weather, and the readings at the radiator, front and back of engine block were all in the low 170's.

Edited by 1941_Saratoga (see edit history)
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All my straight eight chryslers tend to run warmer than the six cars in real hot weather. Including a 1950 NewYorker with a complete tear down-radiator professionally cleaned. Soft plugs removed to clean the block properly, water D-tube removed and cleaned and a new water pump.

They tend to run hotter 190-200 degrees in slow moving traffic and long idling situations but never boil over.

I think it's the way they are in hot weather. I have seen many that the owners say the same.

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Is the rad temp about the same for the complete area of the rad? Hot spots and or cold spot. Is there a shroud? Fan upgrade? I run a 392 Hemi With a 871 blower. These engines run hot also. I cured the problem by adding a shroud, a good electric fan, the best rad money can buy and the most effective thing I did was installing Evans Coolant. There is no H2O in the product. Dissipates heat more effectively. I run this stuff in all my Semi 10 car haulers also. Not cheap. Cost about 1500.00 to do all this myself minus the rad that I had built. Car runs 185 pulling a trailer in 115 heat in Ca. Not bad for a car low to the ground and pushing 600+HP pulling a trailer.

Working with the 348-409 cars (58 to 65 chevs) they ran hot also. My dad was a Engineer back then with GM. They found out the the exhaust was to restrictive. When headers was installed with low flow mufflers, it knocked 20 Degrees off the temp.

If I was going to keep this car and it is said that they run hot, long as the mechs are good, I would do the rad, shroud, air dam below the front bumper, a pull-push electric fan, (fans work is done at speeds over 25) Evans Coolant and headers. Also make sure your rolling resistance is not high. Have car on level ground in neutral with a block positioned about a foot behind the tire, it should roll with your weight leaning against the front end. Hope this helps. Pictured below is my 34 Dodge with the Hemi and the 34 Dodge 3 ton tow truck that ran hot also until we did the upgrades mentioned above. The biggest thing that helped was the headers. Before that, you couldn't drive this truck without it over heating. Has the 217-6cyl 5 speed with a 6.17 gear. A go fast truck-HAHA

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Edited by countrytravler (see edit history)
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Saratoga it sounds like your car is working perfect. In your climate you may not need to do anything. The 160 thermostat should lower your temps 10 to 20 degrees for an extra margin of safety. Modern engines with high pressure cooling systems run up to 240 with no problems. The oil you get today will protect to much higher temps than the oils of 1941.

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Appreciate the responses. I'll go with the flush for now and replace hoses. Still have things to do on the engine and transmission, so I'd rather not spend time on something that probably doesn't need work. I want to enjoy the car a bit this Summer, and when the weather turns colder, lock myself away in the garage and get everything sorted out for the next year.

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  • 1 month later...

Thought I would circle back to this topic, since I finally found some time to flush the system, etc.

I drained the coolant through the petcock in the engine block, and it was surprisingly clean - a little sediment, but no real rust. I ended up running water through the system after it was drained and flushed it 4 times, until a steady stream of clear water came out. I wanted to change out the hoses and figured that I might as well change out fan belt, thermostat and gasket, and the water pump gasket. First surprise was that there was no thermostat installed, so I ended up putting in a 180. I had considered a 160, but was told that the old cars ran on an alcohol-based coolant, vs today's glycol coolants, which are much more resilient (plus a 180 was all they had in stock).

Anyway, I took everything apart, gave the pump a careful cleaning, greased it and installed new gaskets and reassembled. I filled the car with just water, to test for leaks and everything looked good. Took the car around the block and noticed that the temperature gauge was rising pretty quickly, so I came back home and found that water was coming out around the bearing just behind the pulley on the water pump. In hindsight, I wish I had replaced the pump, but I had never had a leak there, the impeller was spinning freely and there was no play in the bearing.

I'm wondering, could I have caused a leak there when I greased it? Or possibly tightened the fan belt too much. Wondering if anyone else has had this happen. Been wracking by brain as to what I might have done to cause a leak. Also wondering if anyone has suggestions on a good contact to rebuild the water pump, or someone who sells good rebuilt ones. Thanks in advance!

Dave

Edited by 1941_Saratoga (see edit history)
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G'day Dave.

I am not familiar with the later Chrysler straight 8 so this may not be relevant to your engine.

I have a 1930 Dodge DC8 which was the original version of the Chrysler 8 engine series.

Basically it is the same engine but does not have the water jacket going to the bottom of the engine on the left hand side and has no water distribution tube installed, and never has.

My car had a long and hard life supposedly having done in excess of 400,000 miles and ended it's original life as a paddock basher for farmer's kids.

When I pulled the engine down the rear cylinder, and to a degree the 7th cylinder had a build up like cement surrounding them which was almost impossible to remove. The rear of the cylinder head was blocked up likewise.

The only way I could clean the block and head out was to remove all the welch plugs and chisel this cement and rust out using modified screwdrivers and welding wire. What appears to have happened is that there was insufficient water circulation around the rear cylinders causing any sediment to settle and build up in this area. The engine would have to come out to gain access to the plugs at the rear of the engine.

This may have been a design flaw in the original engine that was overcome by increasing the water jacket size and adding the distribution tube.

Your car may have had a steel tube installed at some stage which may rusted out.

Also make sure that the water pump impeller is right up close to the pump housing. With the fan always pulling the impeller shaft forward against the pump body wear eventually takes place on both the impeller and housing. I my car's case the fan was almost up against the radiator due to the wear.

All this may be irrelevant in your case but it's food for thought.

Cheers. Jim.

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Hi Jim,

Thanks for the response. Actually, I got good flow through the engine when I flushed it, so I'm pretty lucky there. I found a NOS water pump and installed it. Everything's nice and tight now - no leaks and no overheating. Better yet, I was able to purchase the water pump without giving up the old core, so I'll have that rebuilt and have a spare, in case I need one in the future.

A lot of the rebuilt water pumps have a pressed steel impeller that replaces the original cast aluminum impeller. I can't speak to which one works better, but I prefer having the heavy cast impeller. Anyone have any feedback on which works better?

Dave

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I have no experience on Chrysler replacement water pumps but have quite a bit of experience with Morris Minis and their pumps.

Where I live in southern Queensland, Australia, the area is sub tropical and as the original Mini engine and pump is all cast iron there is no real need for anti freeze to be added to the radiator water.

There are quite a few replacement pumps available made of aluminium with pressed steel impellers. The vanes on the impellers are bent at 90 degrees. I have seen pumps with no vanes left on the impeller after a few years, even when running corrosion inhibitor in the engine. Some have a few vanes missing. All have broken off at the same place. The bend in the steel. Needless to say this severely challenges the cooling ability which is often marginal in summer.

When I buy a replacement I prefer an all iron pump and impeller.

I suspect that the breakdown is caused by the introduction of the aluminium into the system causing some sort of galvanic (?) or electrolysis (?) between ferrous and non ferrous metals. A similar reaction can occur in the doors and bonnets of aluminium bodied Land Rovers where the aluminium meets up with steel. Modern engines absolutely require corrosion inhibitor because of all the aluminium and alloys including zinc used in their construction. In our old engines we can get away without corrosion inhibitor to a point but it is still highly advisable.

Cheers.

Jim.

P.S. Love your car.

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