corvette engine overheating

[smittster]

Hope this does not get too complicated with an explanation. My truck has an 85 corvette engine that I had an electric fan hooked up to come on with the ignition on not thermostatically controlled. I recently added a thermostat control for the fan. After doing this my engine overheats now. The temp never before got over 180 and now it reaches >220 very quickly. Do you think that the engine thermostat finally gave out and this needs to be replaced?

[MrDude_1]

220 is not overheating.
that said, what I would do in order:

1. check fluids.
2. check radiator cap fitment.
3. since you just modded the fan, hotwire the fan just to see if it overheats idling there.
4. if its heating up faster, pull/replace thermostat.. if its heating up slowly, but boiling over id do the radiator cap.
5.. if #4 didnt fix it, id do the other one.
6. check pull and radiator if clogged. on non-cast impeller pumps, pull the pump and look for impeller damage.

[55dude]

checking your water pump impeller is the last thing i would of checked on my DD when i was having overheating issues and was i shocked to find the impeller damm near gone! heard about it on foreign stuff having plastic impellers but not metal.

[MrDude_1]

Originally Posted by 55dude

checking your water pump impeller is the last thing i would of checked on my DD when i was having overheating issues and was i shocked to find the impeller damm near gone! heard about it on foreign stuff having plastic impellers but not metal.

some engines have stamped steel impellers.. ive seen every fin MISSING from them, so its just a spinning disc.. my first S10 had that problem.. the previous owner described it as a "minor overheating issue"...

ive seen cast impellers pitted to the point that the impeller is useless.
and on plastic ones, ive seen them missing entirely.

thankfully, they always seem to go to some magic part of the block, where they dont seem to effect coolant flow... on some engines i cant even find the remains.

[tmoble]

I'd put it back like it was before the overheating started, see if it goes away.

In general, this is troubleshooting 101. If you change something and it gets worse, put it back the way it was first, see if the trouble goes away..

[smittster]

thanks everyone. It heats up real quickly even just idling in the parking spot. When it gets around 225 degrees I shut it off. I then try to restart it right away and it stammers
to start, runs rough but does start, this never happens when the engine is cold or is at around 180 like before. will try pulling the thermostat and replacing it.

[truckdude239]

220 isn;t really hot, every che6vy i've seen runs around 210, i'd check to see if the fan is still spinning the right way

[solidaxel]

You could have a air pocket in the cooling system which the heat gauge is reading steam and not water.

Bleed your cooling system, use a I/red gun to check the temp at the rad, and at the cylinder head, for a accurate reading

Like was said above run battery 12VDC to the hot side of the fan wire and see if it cools the engine down.

The thermostat switch may be too high of a grounding point 220* to turn the fan on.

Keep us posted, do the easy steps first !!

[Thunderwagen]

Is the thermostat you put in for the fan adjustable? If so the on and off temps may be set too high.
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[OrrieG]

I was stressing out after buying a new radiator for my 64 Chevelle DD. It was hitting 220 to in the middle of the winter (10 degree temps). Turned out the 15 year old aftermarket gauge had started reading 30 degrees hot so 220 was really 190. Something else to look at. Also head water temp will read about 10-15 degrees hotter than manifold sensor locations due to proximity to the combustion chamber.

I got a good education on cooling systems in the late 70's working as a garage mechanic in Phoenix. #1 problem was bad caps. #2 was small leaks in bad hoses that caused boiling. #3 were t stats.

[2ndGenRR]

The fact that it heats up very quickly would lead me to believe that you have an air pocket in the cooling system, probably from draining it off and refilling when you installed your fan switch. Run it without the radiator cap to see if you can purge the air. I have seen this a few times and it always goes in step with a very quick overheat problem...air heats a lot faster than coolant.

[MrDude_1]

Originally Posted by OrrieG

#1 problem was bad caps. #2 was small leaks in bad hoses that caused boiling. #3 were t stats.

thats been my experience as well.
I also found that if you tell people this, they wont believe you and do the radiator cap last... ive seen plenty of people replace water pumps, thermostats and radiators before finally breaking down and buying a $5 radiator cap.

[smittster]

My fan thermostat is adjustable, I have it coming on just after starting, probably 100 degrees. I will also try letting out any air in the system. Boy you try to change something for the better and it changes something else.

[tmoble]

if you have a heater hose connection on the front of the manifold that would be a good place to bleed the system.

[dwcsr]

Originally Posted by smittster

My fan thermostat is adjustable, I have it coming on just after starting, probably 100 degrees. I will also try letting out any air in the system. Boy you try to change something for the better and it changes something else.

Set your fan stat 10 degrees higher than your thermostat. Setting it at anything below that isn't going to help on cooling until the thermostat opens an circulates the hot water through the radiator. At 100 your cooling aready cool water thats not circulating into the engine.

[tmoble]

What Dave said.