Overheating LT1 Engine


Asked by cobra1128 Jun 13, 2011 at 10:25 AM about the 1996 Chevrolet Corvette Coupe

Question type: Maintenance & Repair

Yesterday after driving about 15 miles I stopped noticed some fluid on ground did not pay much attention. About 20 minutes later moved car to another spot and fluid ran out again it looked oily opened hood coolant overflow bottle was bubbling over. Let car sit for 5 hours filled radiator with 50/50 coolant drove it home about 10 miles away temp ran about 215 then I stopped at red light dash warning light check guages came on temp went up to 275 and check engine light came on. I continued to drive home temp lowered to 224 got home shut it down opened hood and could hear bubbling noise but no fluid ran out. This morning I took out thermostat put in pan of water on stove and thermostat opened as water heated up to boiling. I put thermostat back in filled radiator scanned for codes found a PO117, Engine coolant temp circuit low input. I started the engine temp climbed to 212 degrees, but the coolant fan did not come on, I turned off engine, I think the fan should have come on at around 200 degrees. Any suggestions to what could be causing this, I don't know  or could it possibly be the coolant fan relay is bad and where would I find this ?

13 Answers

Chase Sutherland

sounds like the fan relay to me. dont know where it is though. try tracing the wiring back from fans themselves and it should lead you to it. should be able to use a voltmeter to determine if the relay is the issue or if its somthing else.


Thank you Chase for your advice. I did try to try to trace the wiring, but it goes in to a larger group of wires and now I have to try and figure out which is which and where the relay is.

Joe Finis Sr.

There should be a temp sensor in the block which tells the fan when to go on, sounds like that's dead. You may want to invest in a 'real' shop manual by Helms, cost over $100 but well worth if you plan on doing any more than casual repairs to the car, they can be found for less on eBay. But my guess is the temp sensor, easy to check if you have the manual to follow the troubleshooting flow charts.


I took the car to a shop yesterday they checked the relays they were ok and the mechanic said both fans were running, could not find a problem, words we have all heard before. I picked up the car and drove it for a have hour the temp went up to 235, I got home opened hood both fans were running. I turned off engine and coolant was blowing out of overflow bottle I started engine being curious and temp rose to 275. Drove car back to shop and he said he does not know whats causing problem take it to a corvette specialty shop, can't get that appointment until June 28. Checked thermostat that opens and closes, fans are running, but it overheats and coolant blows out of overflow. I am confused, could there be a blockage, would a system flush possibly correct ? Has this happened to anyone else ? Suggestions are welcomed please.

4 out of 4 people think this is helpful.

Thank you Joe for your info. I did post another reply after this one explainng some more info.

2 out of 2 people think this is helpful.
Chase Sutherland

Try a flush. Might have some air trapped in the system? If that doesn't work your water pump may be shot.


Thank You Chase for the info I will have that done this weekend and hope for the best.


Took corvette to have a system flush they tried and then after a hour said it could not be done there was a blockage and no heat comes out when you turn heater on. Try a new thermostat this is usually the problem they said. I replaced thermostat still had same problem no heat, overheated coolant bellows out the overflow bottle. Then someone said unhook hoses to heater core and flush out with garden hose, I did this for 3 hours until I saw no more or very little corrosion or blockage. I filled with coolant drove for an hour temp rose to 215 turned on heat still no heat cool air only got home pulled in driveway let it idle opened hood coolant fans were working, no coolant blew out overflow, but turned heat on still no heat and temp rose to 234 degrees. I don't know, maybe its the heater core, please any/all suggestions and info are welcomed. I made an appointment at a local corvette repair shop and the earliet they could give me is June 28, 2011 I hope I can hold out that long. Thanks everyone.

1 out of 1 people think this is helpful.
Joe Finis Sr.

You should be able to rig up something to bypass the heater core easily, that's one way to find out if it the core. You won't have any heat but it's the middle of summer so, no biggie.


Thanks Joe, I guess I could just unhook the hose from the core that goes to the coolant fill tank and hook the other hose that goes from the core to the engine to the fill tank.

Joe Finis Sr.

or if you can get to where the hoses connect to the core on the firewall just hook 'em together there...


I will see if I can find a piece of hose or pvc to clamp them together. Thanks Joe.


mine overheats if my climate control is off otherwise it seems okay???

1 out of 1 people think this is helpful.

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