The Stovebolt Site Forums The Shop Area Engine Shop idling engine overheats

After cold starting and letting it idle for 5 to 10 minutes, my engine overheats. We’ve installed a 292 cu in into my ’53 3600. We’ve attached a triple accessory drive system from Engineered Components, Inc. to mount the alternator, A/C compressor and power steering unit. Since the drive system didn’t quite fit, we swapped the original water pump with one that had a different profile from another engine so we could get clearance for all of the accessories. We are using a 165 degree thermostat and a 1230 CFM electric pusher fan to force air through the A/C condenser and radiator. The radiator is stock and the radiator shop stated that they had never seen an “old” radiator in such good shape.
Wanting to solve this problem first (to say nothing of no brakes and clutch), I have not taken the truck out for a drive to determine if the engine will cool down while it is moving.
Does anyone have any thoughts on this overheating problem? We haven’t tried drilling a small hole in the thermostat flange. Should we start there?

Define "overheats"- - - -does the coolant boil, or does the temp gauge just move into the "hot" zone without boiling over? Have you actually measured the temperature of the coolant? I use an Infra-red thermometer to check the temperature of various areas of the block, hoses, and radiator, and particularly the temp of the area immediately above and below the thermostat.

It's entirely possible your temp gauge is lying to you. What pressure rating is the radiator cap you're using? A 7 lb. cap will allow the coolant to reach 233 degrees before it boils. Go to a 12 lb. cap and your boiling point goes up to 248 degrees.
Jerry

if it over heats that quick you for sure have a problem. how about
also checking you thermostat to see if it is stuck , etc..

obvious if it is running hot then something must be restricting the flow of coolant...let us know when you find the problem

appears you have done a lot of work so might be something within what you did...

like Jerry said, could be your gauge.. or how hot is hot like he asked

Thanks for the good questions, Jerry. We did use an infra red gun and it showed the same (relatively) as the temp gauge. We defined hot as between 185 and 220. It buried above 220 after we shut it down, which I think is expected? I don't know the pressure rating on the radiator cap. The truck is in a shop about 25 miles from home and it will be Monday before I return to it. Meanwhile, I thought I might gather a few suggestions before then. The coolant did not boil over through the overflow tube.

Before starting it, the engine had not run for 4 years. We changed all fluids including coolant. As we adjusted timing, the radiator hose blew off. 35 pounds of cat litter later, we had the shop floor cleaned up. After adding more coolant, the same thing happened--now at 70 pounds of cat litter--but the floor is once again clean! Did we have a "vapor lock" or something like that? I am new to all of this process so I don't mind asking dumb questions.

The "overheating" occurred after we ran the engine without blowing the radiator hose.

Thanks, Redryder. We replaced the thermostat once--went from 190 to 165. I'm wondering if we maybe "downsized" the water pump when we swapped it out.

Compare the size of the impellers on the two water pumps- - - -if the one you swapped for is noticeably smaller in diameter, you're probably not circulating the coolant fast enough, or there's not enough centrifugal force developed by the impeller to move the coolant through the system.
Jerry

Blowing the radiator hose off? Check the radiator cap for one. For another check to see if a head gasket is leaking and excess pressure going into the cooling passages.

Should over take the radiator cap long before it blows a hose off.

If you messed with the timing it can be too slow and it overheat quick. Too fast it likely would grunt when trying to start and clatter bad when accelerating.

About how long had the engine been idling after messing with the timing before it blew the hose off? I think I would be concerned about a bad head gasket.

An original 1953 radiator doesn't need to have more than a 7# pressure cap on it. If you're blowing hoses off you're WAY over that pressure. Are you installing the hoses dry, with no sealer or other lubricant? Try pressure testing the cooling system- - -pump up the pressure on the system and leave it on overnight if necessary. If it leaks down, find out why- - - -maybe there's a leaky head gasket that's letting compression and combustion pressure into the coolant. After an extended pressure test, I pull the spark plugs and then spin the starter. If there's a seep leak, coolant will squirt out of the cylinder where it's leaking. Don't take any shortcuts- - - -assume everything is wrong until you prove it's right.
Jerry

Internet guess..........blown head gasket

Thank you all. I have my marching orders!

Sucking fans are more efficient than blower fans, I know you are short on room between the front of the engine and radiator, did you move the radiator forward in the core support with the longer engine?

Ed

Radiator is in original position.