VCCA Home Forums TECHNICAL - GENERAL Tech Talk 1928 overheating problems

Hi all

Just wondering if anyone has had any problems similar to what I am experiencing....I have a 1928 tourer which overheats when I turn off the engine, and I have checked the water pump, plenty of water passing through the radiator and have removed the thermostat, but when I stop and turn off the engine, the radiator overflows and slightly boils......

When the engine is running it runs at normal operating temperature, I have installed a second thermo sender and temp guage just to be sure and it too shows correct operating temp....

I cant work out why it is overheating?????

anyone else had this problem

Cheers Aussie chevy

Are you running a 50-50 mix of antifreeze coolant and water?
How full are you trying to run the radiator coolent level. My 28 runs about 2 or 3 inches below the radiator cap, run any more and expansion runs it over the overflow. If it runs cool maybe it is just heat buildup from the engine after you shut it down, and it perkulates into the radiator. you might want to install an overflow tank to catch the overflow, . Are you running the engine at idle for a couple minutes after driving, before shutting it off?

The problem is most likely air entrainment. It is a topic that has been discussed on many occasions but needs to be repeated as most people are not well versed in the problem.

Air is drawn into the coolant. The primary source is past the shaft on the water pump but can also be at hose connections. It will happen even if no water leaks! This air circulates in the water passages in the engine and because the pump produces some pressure when the engine is running the air bubbles are relatively small. Once the engine is stopped the pressure inside the engine drops and the air bubbles get larger. At the same time heat that remains from combustion in the cylinders and not already transferred to the coolant increases the liquid temperature further increasing the size of the air bubbles. It is the expansion of the air that forces out the extra coolant.

Tightening the packing on the water pump to eliminate the air is one step. Another is to install a overflow tank on the radiator overflow tube. Try to position the tank as high as the top tank or as high as practical. That way the coolant forced out will be taken back into the radiator as it cools or the air bubbles are reduced in size.

Unfortunately antifreeze mixtures are more prone to foaming and water loss from air entrainment than plain water. There are antifoam agents that can be used.

The air entrainment problem is much more common in non-pressurized cooling systems. It is one reason that modern cooling systems run at 15 psig. There are several others like higher boiling point!

I will second what Chipper said Air can get sucked into water pumps even on modern cars, and add one more that is related. There could also be a flake of rust in the head causing a "hot spot". A flake of rust won't let water circulate under it even though water may be able to get under it part way. It soon gets hot enought to boil the water and cause a steam pocket under the flake and if it is big enough and the water gets hot enough it can cause a steam pocket to collect in the top of the head water jacket. Usually if there are steam pockets forming, you will hear it start whining like a pot of water on the stove starting to boil but it won't last long after the engine shuts off. You may have to use a stethescope to hear it if the engine is running and even when the engine is off since the iron is so thick in the head. Try the stethescope on a pot of boiling water to get an idea what you should listen for. One other thing A very tiny crack can do the same thing, it may let just a little poof of exhaust into the water jacket when the cyl fires and cause the pockets of gasses to form in the head. Some auto parts stores carry chemical test strips for head crack/gasket problems. They test for exhaust gasses dissolved in the water.

Thanks everyone

I have been running a premixed anti freeze coolant in the system, and have flushed the system to remove any rust and particles that may be in there too, the only thing I havent got is seperate overflow catcher which sounds like a great idea....I will also check for air getting into the system, as there does seem to be a lot of small bubles in the water when it gets hot...

I will check all of the things that you have all told me about....many thanks and happy motoring

Dave Aussiechevy

They all do this to varying degrees.I have been driving my 28 for about 18 years and cover 2-3000 miles a year. The important thing is "Does it overheat while you are driving along?". If it doesn't you are going well.
I live not far from an expressway and I wander along at about 45mph. I know that when I ramp off the traffic lights will turn red and I have to stop quickly and "whoosh", water everywhere. Simply the engine is hot and suddenly there is precious little air flow and the water temperature rockets.
What I do is to back off several miles before I ramp off; just a bit at a time so that when I reach the ramp it is all cooling down and if I have to stop it doesn't boil.
Beyond that I never turn the engine off immediately after stopping. I just retard the ignition and let it idle a while before switching off.
The other things submitted are also important and play a part in it all. Hope that this helps.

I'll have to go along with Terry. Once I asked my Dad about this thing of having to top off the radiators in the pre 1930 cars, he said "That is why they put the radiator cap on the outside of the hood, so that you can get to it easy." It isn't "overheating" unless it is steaming and loseing ooolant, and messing up the windshield as you are driving, just the fact of driving an old car, however I found that Old Klinkerbelle don't do that when the water pump is re-packed every couple of years, so that it don't suck air around the pump shaft. Chipper will clue you in on this little quirk of these old cars.

???????

I have no idea how I reposted Macks reply.. It was unintentional please disregard.

Roy,
I guess it was the cyber gremlins that have frequented this site for the past month. They are working to frustrate all of us, most of all BB.

Hi,

What is the average running temperature of a 1928 using a infrared thermometer? The return hose to the radiator is around 160 and 212 on the head at the #4 cylinder. This is after 20 minutes of driving at 5 mph or so. I had a gush of 50-50 coolant come out when I shut the engine off but the level was just a 1.5” below the cap before driving and my overflow container is just a 20oz beer bottle which apparently isn’t large enough. Thanks in advance!

What was the outside temperature when those measurements were made? 5 mph uses mostly the fan to cool the radiator. As speed increases ram air does most of the cooling. If coolant gushes out shortly after the engine is shut down air being sucked into the cooling system is highly suspect. Most likely past the packing on the water pump.