my 92 is overheating.

I have replaced the thermostat and the waterpump.

There are no signs of leakage from the radiator or on the heads.

Suggestions please?

 

1. Did you use the bleeder screws and purge the air out of the system properly?

2. How hot and when?

 

yes, i have bleed the system several times, using the bleeder screw on the throttle body.

and it gets to operating temp, then slowly climbs to 260, then i cut it off.

it overheated one afternoon after i floored the pedal on the highway.

 

Sounds like there still might be air trapped in the engine. Take the surge tank cap off, run it up to op temp so the t/stat opens and bleed it again, then top it off if necessary and replace the cap. Use the bleeder screw on the t/stat housing. Also check for debris in front of the radiator.

 

Make sure the air dam is clear. Also make sure the radiator fans are coming on.

 

Stupid question is this the correct T-stat. LT1's need the correct one to work right.

Make sure the fans are coming on.
Do the hoses get hot?
Warm air from radiator with fans on?
Any heat? If no heat, classic sign of air pocket/low coolant.

 

Question is WHY did you replace the water pump and stat? Was it overheating and this was an attempt to fix or is overheating a result of this work?

Also, after the engine warms up feel the temperature difference between the upper and lower radiator hoses. If circulating one should make you cuss and the other one will be pretty hot.. but not as bad as the other(I think the passenger side one). If just one gets very hot and the other stays for the most part, cool, you may have a bad pump or a stuck thermostat.

 

Okay.

The throttle body hose (driver's side) = very hot
The thermostat hose *passenger side) = mildly hot

This means there is circulation and the thermostat & waterpump work correctly ... (right?)

The fans are not coming on as far as i can tell.

Yes, this was to fix an overheating problem. I changed the thermostat first, then realized there was a grinding noise from the pump - so i replaced the pump.

 

My '95 would overheat at red lights, but as soon as I started rolling, the temp would come down. I found a blown fuse for one of the fans. After replacing the fuse, the issue went away.

You should try to find out for sure whether or not the fans are coming on. According to the FSM for my car, the fans come on at low speed at 226F and high speed at 235F.

 

okay the fans do not come on... where is that fuse etc...

 

If neither fan is comming on I would check the fusable link and the connector from the batt + terminal. Easy check is to pull the fan relay and see if there is +12Vdc on the power pin of the relay socket.

BTW, does it overheat on the highway or just when sitting in slow traffic??

 

You need to remove the cover over the radiator and visually inspect the void between the radiator and AC condenser.

This is a place where debris WILL collect. GUARANTIED!

 

I'm not sure if the '92 is the same as the '95, but, if so, I would first check the two fan fuses which are located in the underhood fuse block (near the battery). i believe that if the fan 1 fuse is blown, neither fan will come on.

 

This was my issue,
My car was getting hot in traffic, on the highway it was ok, i started looking for the problem and was about to change the fan control module. while under the car i grabbed the plastic fan to spin it and see if it was free. It hung up and didnt spin freely. After moving back and forth it came free but i could hear rocks inside the shroud cover. i took an air hose and blew it out. No more issues. i couldnt belive it, this was a three month issue and a thermostat change. If i had taken it to the shop there is no telling what they would have said the problem was. I just wanted to share this because i felt pretty stupid. There is no way stuff that gets blown in the shrould can work its way out. It doesnt take much to stop the fan from turning. Just a perfect example of checking the simple stuff first especially if you accidently end up on dirt road. Hopefully this will helo you if you are having the same type of issue.

 

Does it overheat in the cooler months also?

Where do you live/drive? Is it in the 100F range? If so, not sure if you have the extra pusher fan on the front, or not, but if you do, you can swap it out for a larger high flowing fan, possibly a zirgo 14". I have a zirgo 14", but mine is an early C4, and clearances might be different. It made a world of a difference.

If you don't have the extra fan, you can wire one in with a new fan switch and relay. You can pick a switch that will come on whenever you want...maybe on at 205 and off at 195 or something. If you live in a really hot climate, like I did (abilene, Tx), now TN, the stock cooling should keep you in the 220-230 range (my dad had an lt1 and lt4), however it can easily get over that, and to get a little more insurance, you need some fans coming on before it gets up there...it just needs a "head start" in that kind of heat. Advancing idle timing and A/f in ecu can help too, but then you increase emissions. (Lt1s may already be pretty advanced at idle...may be the reason for precats in the later c4s).

Still sounds like a main fan or air pocket issue, though? If it's just fans, it will start to cool down tremendously on the highway, as long as your uninterupted.

 

okay, so i took to a shop.. they said i need a new head gasket; i did ask them to run a compression check.

any ways to verify that (i can't do a compression check myself)

oh, and suggestions on parts and estimate on cost (i don't have tools here in louisville to do it myself)

 

absolutely do this #1 before you do anything else. Next add water wetter to your colant. Best $10 any vette owner can spend. #1 check the void between the radiator and condensor. I couldn't believe the crap I pulled out of there on my car. I put a screen over the entrance to block stuff getting in.

 

There are 2 bleeder screws on a 1992. You say you only used the one on the throttle body. There is another up near there but very well hidden. You need to use it also.
Clean out the junk from your radiator.
The fans do not come on until the water temp is 229. Then one fan will come on. At 239 the second fan comes on. I am going from memory on the temps so they may be off a degree or two.
If you turn on your air conditioning both fans should run all the time.
Are you using the temperature from the guage on the dash or are you getting the temp from the digital readout? The analog guage is generally useless for telling the temps. It is not linear and is only an indicator. For an accurate temp you need to use the digital readout.

 

Did the shop performed a block test to support their decision...yes you could have a gasket issue, but I would exhaust all other Possibilities first.

 

You need to find out why the fans are not turning on! A head gasket should not prevent the fans from working. Good luck with it!