The Stovebolt Site Forums The Shop Area Engine Shop My 292 is running hot

I had to replace the engine in my 1953 GMC 3 ton with a '66 292 from a bus. The original radiator had some plugged passages in spite of several flushes, so I rigged a second radiator in front. At first it worked fine, but it eventually started getting hot again. Turned out, the plastic fan I attached to the engine(metal one was too big) made the bolts go loose and therefore, the belt loose and stopping the pump. I had already ordered a new radiator, so I put that in. Removed the plastic fan, since I had added a dual electric fan from a truck. Though it was a 3 row and not the 4 I wanted, I wasn't going to be hauling at it's max capacity.

It was still getting too hot.

Recently I added back in the second radiator. While I was at it, I checked the timing. Good thing as it was off. (Advanced? Don't remember, looking from the front as you would for timing, it was to your far left.) I gave it another flushing as I noticed there was still rust flakes in it, despite a previous flush. Let it sit over night with rad flush, vinegar, and rust remover. Then I connected the garden hose to the rad, then the block at separate times. Let the water run for a while. After, I also added that 'water wetter' stuff. While testing, it got up to operating temp and seemed to stay there. Then I gave it a little gas and kept it there. Seemed to slowly creep up, so I didn't risk a test drive. During a previous drive, it seemed to go up slightly faster while accelerating. Makes sense, 'under load'. Though, the pump should be running faster then. After installing the second rad, I looked in it and the water was flowing, showing the pump works.

All I can think of is the fan isn't up tight enough to the rads, or that little plastic fan that was on the engine somehow made a difference? Also, I don't remember if I replaced the temp sensor when I installed the universal temp gauge. The rads never boiled over when it said it was as high as 240.
The engine runs and works great.

What do you think?

If you are not running a fan shroud you should be. Then you need to determine if your engine is really getting hot. If it is then start figuring out how to clean the passages in the block. Clean radiator, clean block, good water pump and a proper fan and shroud you should be good to go.
I’m sure others will have some different ideas for you.

My 52 3 ton also has a 292, replaced by PO. The fan tends to sit a little low for the stock rad, with the standard water pump, however, with a fully flushed origin rad, and my 292 was rebuilt so very clean passages, it runs 180 all day unless very hot outside and I'm idling.
Did you flush in reverse to standard flow path, sometimes that breaks some gunk loose.

Might also check for air lock in the cooling system, make sure the highness point has a valve to let air out!

Ed

Does the thermostat housing have the bypass hose installed? Where on the engine is the temp sender mounted? Have you pulled the drain plug on the engine block ( drivers side towards flywheel ) to see if coolant comes out? With two radiators? you will need heavy duty fans to pull air through both units. You need the biggest solid blade fan you can it in place.

It should be possible to mount a belt drive fan that centers on the radiator with some pillow blocks and a jack shaft, and install one that's big enough to move the right volume of air. There's a good reason most airplanes use engine-driven propellers instead of an electric fan up front.
Jerry

1. Replace the temp sensor. 2. Determine if the stock Rad was 2 core. If the rad was, there might not be enough air flow through a 3 core plus the second rad out in front of that.

If the temp sender is in the head, between #1 and #2 cylinders, it will read much hotter then under the thermostat. Being close to the combustion chambers is really hot, mine dropped 30 degrees when I moved to the thermostat housing.

The temp sensor is at the thermostat housing. I have been busy with work, but did make a fan shroud and seems to be much better air flow. While I was at it, checked the coolant flow. Moved well through the main rad when the thermostat opened. Still need to take it for a test drive.

There is a bypass hose.
The old rad was very thick, but couldn't see inside to count cores. It is a 3 ton truck.
Was going to reinstall the crank fan, but not enough room to remove the bolts with the rad in.

Update:
Checked the block drain plug, coolant came out.
Just took it for a test drive, ran just fine. Seemed to stay at 210, if the gauge can be trusted. The "universal" voltmeter says less than 12v, but the multimeter said over 13v.
Might also try a lower temp thermostat later.

Changing to a lower temp thermostat will not have any effect on the maximum temperature of your engine.

It could lower the temp if the coolant system is working properly. I would not go lower then 180. Its true about upper temps, once open, the thermostat is just an open hole doing nothing, the temp can go as high as it wants at that point.

Glad its coming together for you.

“If the gauge can be trusted” is a big if, make sure you are chasing the right problem.
stick a bbq/meat thermometer in the radiator, my thermometer was within 1/10th degree (when I compared readings to a Fluke meter).

Running engine with cooler t’stat does not help engine longevity, need hot, 180 or so to burn off water generated by combustion, make heater produce heat, especially on short trips. As Jerry has said, if it is not boiling over, it is OK!

Ed

Thanks!

When I disassemble an engine for a rebuild, I an usually tell by the wear pattern on the pistons whether or not it has been running a thermostat. Pistons aren't round- - - -they're "cam ground" with the biggest diameter 90 degrees from the wrist pin. 45 degrees from the pin hole, they're several thousandths smaller. They get round as they reach operating temperature due to anti-expansion struts cast into the piston when it's manufactured. Engines that don't get up to normal operating temp regularly will have a shiny spot about 3/4" wide in the center of the piston skirts that's been carrying all the load, and varnish built up on the rest of the skirt where it hasn't been making contact with the cylinder walls. The cylinders will be worn egg-shaped, also. Running an engine with a too-cold thermostat or none at all is pretty foolish.
Jerry