VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1929-1932 1931 Chev pickup

Could someone please help me with an overheating problem I am experiencing. When I take my pickup for a ride temp guage runs in normal range. When I stop at a stop sign I can see gage moving up towards hot once I start driving gage goes back to normal. When I get back home shut engine off gage goes very quickly to hot and I get steam coming out of overflow and radiator cap. I should have mentioned I have anew aluminum radiator installed, engine thoroughly cleaned and rebuilt , 4 blade fan and new water pump. if I put a fan in front of radiator it cools down quickly. I heard the the engine block design for water flow and cooling was not the best in 31. If someone could please share howto keep-engine cool at idle or when engine gets turned off after a ride has been completed
ThankYou

Your symptoms are a typical example of air in the coolant. Most often the air is drawn in past the shaft of the water pump but other sources are possible, like loose enough hose connections that don't drip coolant.

could be air as Chipper noted, i installed a GANO filter on my return line to be able to see if there was air.

what are the ambient conditions outside ?? hot humid ?cool and dry ??

other thing could be HOW NEW is the engine ? is it the rebuild still and still being broken in or got excess of 500 miles on it ?

i finished up a complete rebuild on my 1929 recently and with the temps in in the upper 80 and more plus humidity around 60%+ here on the coast my 1929 runs hot after about 5 minutes of driving, i was told need to break it in and take it easy and should loosen up and cool down. got maybe 50 miles on it, only drive it at evening and if the temps are under 80. it does not get as hot as fast, still breaking it in. cool weather coming so will drive it more :) plenty of post on here by me about this and the input provided by Chipper and others !!

also heat soak occurs when you drive them stop and turn it off. typically for all these old cars. i could drive around and once i park temp slowly rises 10+15F and then starts to cool off.

Just came in from garage. Found lower water pump hose clamp loose needed a tightening Had dried antifreeze crystals on clamp. Checked out all other clamps and bolts Snug up everything. Test drive tomorrow we have rain here today. I’ll give you an update later
Thank You

I let the engine idle with radiator cap off two different times for 20 minutes during this running time car stayed within normal temp range. Took the pickup for a ride and engine ran in normal temp range, stop at stop sign and temp went up to just below red. Continued for the rest of drive temp stayed in normal range. Got home shut off engine temp rose into red high temp range Took a couple of hours to cool off just sitting, outside temp 68 degrees and overcast. I checked radiator coolant and it covers radiator core up to bottom of top entry. I answer to question regarding miles since engineers rebuilt approximately 75 miles
Any advice would be appreciated

what water to green coolant ration are you running ?? most do a 50:50 i am running a little thinner like 60:40 more water.

really sounds like same ordeal i had here, new tight engine and everything having to break in and settle.
if you want to make sure it is not air do the Gano Filter. then you can SEE the coolant. I have the Gano on mine and NO air :) just a new tight engine with parts settling in and mating up.

picture of Gano Installed

here is a video clip of BEFORE i rebuilt my engine with the Gano installed you can clearly see the air in the system.

Hello Independence,
Agree with air somehow entering the cooling system. Even with only 75 miles with fresh engine, the engine appears to have gone thru a fair amount of heat cycles. Expansion and contraction of components could compromise gasket sealing. With a Gano Filter to allow observing the coolant, it would be interesting to test the cooling system with and without the engine running. Figure out how to drive the water pump with the engine turned off, any air? With engine running, any air? Could cylinder compression bleed thru head gasket into coolant system? Should head bolt torque deserve a re-check? Compare coolant total quantity/amount stated for a stock 31 pickup to the total quantity/amount that your aluminum radiator setup allows. Keep us informed so we also may learn.

Now that it’s cold weather in Minnesota I will have some time to work on my 31 Chev pickup. The problem that I was seeing every time I drove the pickup, engine temp ran fine as long as I was moving. Short stops at stop sign didn’t have much effect on rising temperature to the gage. Get home shut engine off and no water pump circulating. Temperature gage in dash would rise fairly quickly into the red zone. If I let it cool from heat dissipation thru hood about 30-45 minutes to cool down. If I put a fan in front of radiator it cools down in 10-15 minutes. So I wanted to know is this normal when you shut off engine after being driven when the engine heat is too great at back of head where heat gage sensor is or is there something I am missing in the cooling process. I was thinking of removing enclosure pans from frame to engine to see if that would help heat to get out of engine compartment quicker The other thought I had is putting 12” 6 volt fan above engine so when engine is off I would turn on fan to circulate heat out hood vents Your thoughts please

Your experience is normal. The heat in the block has to dissipate which is a much slower process than if the coolant is circulating with the pump.

sounds normal, same with my 1929 here
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