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Specialdeluxe47

Cooling system 1947

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1947 Plymouth Special Deluxe; this car has the original motor it has been rebuilt. The car runs hot all the time. Before I start tearing down I wanted to ask if any one has any suggestions before I Start. I have a 180 deg thermostat, sitting still in idle it will open the thermostat. In all the pictures I have seen of 1947 flat head six engines the water pumps look like they are external by-pass because they all have the hose that runs from the pump to the thermostat housing and my does not have that does that mean mine has been changed or where some produced like mine I have enclosed pictures.

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Edited by Specialdeluxe47

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It appears you are running no form of thermostat bypass. Thats the later model water pump that doesnt allow for the bypass housing. And it appears someone has closed off the bypass opening in your thermostat housing.

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Then, there's the possibility of the clogged water distribution tube as

well as water passages inside the engine.....with the typical rusty

gunk. Have the "freeze" plugs ever been removed and the passages

flushed? Is your radiator working as well as it should?

Just a couple further thoughts.

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Simplest test is to remove the stat and see what happens, it if takes longer to heat up or rus cooler then you can probably address it by un mixing the metaphore so to speak.

What kind of conditio is the coolant in, is the system full of rusty coolant.

You also should go the the main page of the host site and read up on water distribution tube, and its care and feeding.

Also something simple is the belt tight??? does the hose that feeds the heater get hot is the retur hose hot?

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The Coolant is in good shape clean and somewhere around 70% water 30% antifreeze I will try removing the Stat and see if anything changes. The freeze plugs have never been removed as far as I know. The engine was overhauled about 30 years ago and has less than 1500 miles on the car since then. I did not want to check the tube until the last. Do you guys think the water pump and stat housing has been changed out the paint on both seem to match the rest of the engine? Even my repair manuals show that it should have a by-pass system on it. Would that keep it from overheating?

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Before fooling with the distribution tube, I would have the radiator flow tested. A radiator, even partially plugged, can cause the engine to run hot especially in hot weather. Good luck to you.

John R

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there's also the minor detail of the temp gauge. Have you tried putting a candy thermometer in the top tank to find out what it shows? I had always thought that my car ran hot until I found out that my gauge read 20 degrees high. Several years later I got a new gauge and calibrated it before installation; much better!

Marty

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Does the front of your engine block have the "bump" that would indicate the internal bypass? If not then I would suspect that you are missing the external bypass.

Jim Yergin

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Thanks all who replied there are some good sound steps I can use to diagnose the problem.

But Jim could you describe this “bump” or provide a picture? I would like to learn more.

So can anyone tell me if this water pump setup I have here is Factory for a 1947 or has it been changed. I remember when my dad got the engine rebuilt 30 to 35 years ago, he was pretty mad at the guy who did it for him so maybe it was change at that time.

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here is my 2 cents worth. My 47 also ran warm. 180 thermostat. but when its really hot out it will go to 200. First thing I would check is the radiator, in fact I would flush it and the block just be sure. The bypass is/could be an issue. But believe it or not, timing was my issue. I had it advanced too much, runs cool now

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Thanks all who replied there are some good sound steps I can use to diagnose the problem.

But Jim could you describe this “bump” or provide a picture? I would like to learn more.

So can anyone tell me if this water pump setup I have here is Factory for a 1947 or has it been changed. I remember when my dad got the engine rebuilt 30 to 35 years ago, he was pretty mad at the guy who did it for him so maybe it was change at that time.

Yes that is a newer water pump. Belongs with this type of setup. Sadly you can't see the bump at the front of the head.

015_11A.jpg

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Well Thanks again for all the good ideas on this engine runs hot problem.

I was able to try a few of them this weekend. The temp gauge reads 212 and the water in the Radiator is at 200 about a ten degree difference through the entire range which looking at the location of the temp sensor and then the top of the radiator I would think it is about right. It was 92 degrees on Saturday here and with a 180 degree thermostat it was running about 200 until I had to climb a steep hill then it went up to 212, but back down to 200 down the other side. This week I will remove the Thermostat and see the difference, do a radiator flow test and check my timing. Speaking of timing is there something that I need to do to the distributor to compensate for today’s higher octane and non-leaded fuel?

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fuel is actually better today than years past, the only problem might be 10-15% ethanohle that is in most gas, but has not been a problem for me at all. you do need the bypass hooked up, and the proper t-stat installed, the one that is very large not the small flat one. flat one does not allow bypass.

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A lot of folks run a hair more advance for modern fuel, I am runing good at an idle setting of 6 BTDC.

As a note we need to refrain from refering to the different by pass systems as early or late. My early 45 had the internal bypass system as did my late 56. So the date of manufacture is not a determining factor as to which system your car was built with.

External has a rubber hose between the large cast iron thermostat housing. The internal systen has a smaller pressed steel stat housing and no hose. The bypass is done through the block and back of the water pump. The water pump and gasket are specific to the system employed.

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Update;

I have check the timing-OK

Flushed the System - Clean

Checked Thermostat - Bad does not open at all even past 212.

Replaced water pump with rebuilt original from eBay

Replaced Thermostat housing and thermostat from eBay

I have a question in my parts book and Maintenance book there are two gaskets that go with the thermostat one with bolt hole that seals the housing and one that goes on top of the thermostat to seal inside the housing.

I need to know what a suitable substitute there is and where to get it from for the gasket that sets on top of the thermostat. Is it rubber or paper? Can anyone help?

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Test it before installation by submersing it in water then heating the water. with a thermometer you can ascertaint its operating temp range. Remember the temp rating on the stat as the temp at which it opens not necessarilly the temperature at which the egine will operate it.

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No it looks like this. But that is ok I found one at Andy Berbaum's

The one you pictured and the one I showed are interchangeable. The one I have is available new at napa for about $10 and in either 160° or 180°

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