1986 corvette overheating problem.

Asked by Sep 03, 2012 at 10:36 PM about the 1986 Chevrolet Corvette Coupe RWD

Question type: Maintenance & Repair

My corvette is overheating after replacing the gaskets on the intake manifold and cleaning everything else out. I replaced the thermostat, fuel injectors, IAC. I put it all back together and it starts up just fine, however the coolant temperature climbs up to 220F degrees. I put in a 180F thermostat and filled the coolant up to the designated level. I don't know what to do or what the problem is.

25 Answers


look into a 160 degree thermostat and maybe a higher pressure radiator cap....to me 220 isnt exactly over heating, like 40 more degrees or so would be bad but if it doesnt go over 220 u should be fine...correct me if im wrong but on most cars the middle line is around 220, mine says its too hot at 260 and coolant will be boiling out of my reservoir

4 people found this helpful.

Burp the cooling system, chance is you may have an air bubble in the system. How much Sealant like RTV silicon did you use?

3 people found this helpful.

I used some rtv around the thermostat and other places where it needed it like around the head gaskets and some bolts.


was it allowed to dry before coolant was added? I've had clumps of the stuff gum up my thermostat once. Heard of it clogging other things, as long as it wasnt used exsessivly it shouldnt be an issue. I would try burping the air out before considering it.

1 people found this helpful.

220 deg is a very slight problem.. it could be tiny bubbles, clumps of sealant, deposits on the radiator, pin-hole leak. if your radiator is the age of the vette, check for cracks. mine wore out at 20 years of use.


I'm just curious as to why his 86 is carbureted since GM put fuel injection systems on the 84 and newer vettes. that's why it skipped a year of production because of the fuel injection issues. Does the car have 2 cooling fans? Sounds like the primary isn't kicking on BC 215-225 is where the backup kicks on. Did it get plugged back in? It is also known as the a/c condensor fan.

2 people found this helpful.

Pressure test your cooling system, A heater core leak can give you that kind of heating, and a lot of vetts do not show the leakes, very easely. Also make sure the A.C. is charged up, thus ,causing the second fan systum from working.

2 people found this helpful.

i was under the impression that the degree thermostat just determines when it opens up and allows coolant flow, so if it opens sooner, isnt that better....im learning too

1 people found this helpful.

Michael you have it completely backwards. A thermostat rated at 160 will begin to open around 140-145 allowing the coolant to flow from the block to the radiator in an attempt to keep the coolant from actually reaching 160. Once the coolant reaches 160 the thermostat opens completely in an attempt to prevent the engine from getting any warmer. You could completely remove the thermostat leaving a value of 0 BC it would technically always be open. Doing this would cause the engine temp to run very cool while driving and it would take forever for the engine to get up to temp. Once a vehicle begins to drive the fans quit all together because the movement of the vehicle causes airflow over the radiator. If the temp continues to rise then the fans will kick on at their predetermined temp. If the primary fan fails to keep the engine below 215 then the secondary fan will kick on to handle the extra heat. If the primary doesn't kick in then the secondary will just kick in at about 215 cool it to around 205 then kick back off. You can remove the entire ac system on the car and the secondary fan will still kick on. A leaking heater core won't cause the car to get hotter unless lots of coolant leaked out. The only thing a leaking heater core would do is allow the coolant to boil at a lower temp because the system can't build pressure. And as for the comment on a carbureted car running at 220 is ridiculous. VAPOR LOCK a carbureted car needs to run at 180-195. Only reason I didn't mention that earlier was BC this car doesn't have a Carb.

1 people found this helpful.

Ahhh so what you're saying is that the radiator is pointless and it only makes the car hotter???? I'm soo glad I wasted $24000 to become ASE certified and learned the wrong stuff. Let me guess on this one too..... cars with an automatic also have a flywheel. Funny how I found a thousand sites like this one where they agree with me on disagreeing with you but none to back you up!!!!!! http:// auto.howstuffworks.com/cooling-system8.htm Stop giving false info!!!!

1 people found this helpful.

To answer Andrews question about letting the rtv dry. I did not let it cure before I started the car up. It might be clogged with the rtv gunk in the radiator or the thermostat. Good point. I didn't think about that. I might have to buy another thermostat or just use the old one.


If there is gunk on it then you can clean it and it should work fine.


my trans am has a heating problem too, but the biggest issue is that i dont have a grill, just an air damn under the car, so i upgraded my fans and radiator....also wired my fans to a switch so i can turn them on in stop and go, and off on the highway...i mean i have two fans that spin at 5,000 rpm, so its like im on the highway anyways lol


*had a heating problem

I replaced one of the radiator tubes and it fixed the problem!


btw, the bottom radiator tube used to have a coil inside to prevent collapse.. does anyone know why it is not done anymore?


radiator flows opposite direction than it did 30 years ago.


It flows into the top of the radiator and out the bottom it used to flow different?


OK. I apologize for the error. I didn't realize we're talking about an 86 here. Starting in 92 with the LT1 the water flow is reversed, this eliminates the negative pressure on the lower hose causing them to collapse at times. So the modern Corvette flows from bottom to top.

1 people found this helpful.

I have seen gaskets put on that were a universal gasket. Sometimes the water jacket holes in the gasket are not punched out. If you replaced the head gaskets, you may have to pull the heads again just to make sure all the water hoses are not blocked. If the gaskets you put on does not have anything to do with the radiator water, forget this. Sounds like air in the system, or a weak hose collapsing, or a blockage somewhere. If you have access to a temp gun, when the car is heating up, check for hot spots in the engine. This may help you in starting to locate a possible blockage.


This issue was resolved 6 months ago


'86 Corvette's are designed by the factory, to get that hot. My fan turns on at 223-225, than cools to 180. I thought that was a problem before to, until I talked to a Corvette expert. Only gets that hot in town or city driving.

2 people found this helpful.

what was the problem?

1 people found this helpful.

Radiator hose fixed the issue, bottom house was probably collapsing...

1 people found this helpful.

Thanks, and enjoy your ride.

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