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I have a friend with a '36 120 convertible that has been over heating since he bought it. He has been told that the Junior cars of that period are know to have an over heating problem. Is that true?

He has flushed the radiator, the engine and inspected the water transfer tube.

Thoughts and comments would be greatly appreciated.

First I have heard about it. Also, not any Service Letters pointing at a systemic issue.

Radiator
Water Pump Clearance
Thermostat (incorrect one/style)
Partially Clogged Exhaust
Ignition Timing
Blown Head Gasket (Hot Cylinder gasses leaking into coolant)

Also, a flushed radiator doesn't mean it isn't still partially clogged or someone in the past has pinched off some tubes to fix a leak.

Partly plugged radiators are very common. Grease, rust deposits, lime, and loose rust flakes afflict many old radiators. It can be very difficult to get one clean. Some radiators with straight tubes can be "rodded out". I don't know if the honeycomb or cellular style can be.

Water pumps can leak air in at the shaft seal and cause overflow and overheating problems. This can happen, especially at higher engine speeds, even if the pump doesn't leak when sitting. A clogged radiator can aggravate this condition.

Good afternoon...The enterior of the cooling system inside the engine can also be quite filthy. On our 49-288, we finally removed the freeze plugs and put the head of a power washwer into the interior and my goodness what stuff came out of the lower hose! Engine was much happier...Also the same sort of pressure needs to be applied to the interior of the head...Ernie in Arizona

Many old cars were run with soluble oil in the cooling system, and old style water pumps could force oil or even grease into the system. The oil would mix with rust and form a gummy, waxy material that resists many types of acid or soap. Hot-tanking old radiators can be effective, if you can find a shop that still does it.

The entire system needs to be clean and the engine needs to be in good condition and in proper tune for best results. Air can leak into the system when the engine is running due to radiator pinholes, bad or loose hoses, or a bad water pump seal. Air in the coolant can mimic boilover, and will lead to overheating and other issues.

Hi Marty,
Good points by all responders. I think the point(s) here is that overheating can be one issue or a combination of cooling shortcomings that can lead to the wrong end of the temp gauge. Kevin mentions 'water pump clearance' and this is, in my opinion, an oft-overlooked possibility when troubleshooting overheating. These pumps are very old and have likely been through the reuild process more than once. As corrosion and wear eat away at the 'innards' of the pump, the clearances can become past tolerance specs and while the pump doesn't leak and pumps water, the volume it pumps is inadequate to cool the engine, especially in hot weather. Not sure about the '37, but I know the '39 pumps have been re-proed and they are quite reasonably priced. Also, I am a firm believer in rebuilt rads. Additives and flushing can help with an old rad, but that doesn't come close to the benefits of a fresh recore and the descaliing of upper and lower tanks that come with a radiator service. Rad shops are getting scarce these days as they don't rebuild car rads anymore, but there are still quite a few truck rad guys out there that will be able to help. Not cheap, though.
Chris.

Thanks for all of your inputs as they are great areas that can lead to over heating. The car has been a "Trailer Queen" with very few miles on it since it was restored.

I had never been aware that the 120's in that era had a history of over heating, which was my main concern.

To add another possible cause to the basket is the wrong head gasket or installed backward.

I plan on running the car an using an infrared thermometer to examine the radiator for hot spots. Will probably pull the head to flush it and ensure that the gasket was correct (P.S. will use a new gasket.

Again Thanks to All

I want to replace the thermostat in the car. In the Cross-Reference section I see a Napa #70 will fit in a '38. Will it also fit the '36?

Radiator and engine were flushed, which appeared to help some. However, it appears that the main issue was probably with the thermostat, which was replaced.

That being said, HF sells an infrared thermometer for only like $20. But I doubt it will help much if it's a head gasket issue. I would suggest a kit to test for exhaust in the coolant.