wm_sorg

Hi All,

Does anyone have a good write-up on replacing a thermostat on an 86 corvette? Most of the stuff I found here was for LT1 c4s. Normally I would tear into it, but I want to be careful not to damage any of the plastic vacuum tubing, etc.

Thanks for your help!

Regards,
WS

armybyrd

It's pretty simple. Two bolts for the water neck and viola.

Cjunkie

Get yourself a throttle body gasket and take that off.

vader86

Nothing really to it, you can remove the intake duct to the TB and its just two screws holding the housing on.

Take old one out, put new one in, add sealant, check for leaks and burp the system by letting it get up to thermostat-open temp with the radiator cap off and the idle held up to about 2000 rpm, fill and replace cap. Done.

Dt86

When you remove the egr solenoid that mounts to the thermostat housing just be careful with the vacuum lines that run off of it. There are two. One goes to the bottom of the throttle body and the other one goes under the plenum to the egr valve.

Kmoylan

My 89 c4 is running at 250% or more. Is this normal or what??? Cooler therm?? How bad is it to DIY, I'm no mechanic!!

Whaleman

This is something I have posted many times but I repeat. EVERYONE talks about the opening temp of a thermostat. 160-180-190-195. But NOBODY talks about when the thermostat is FULLY open. Thermostats should be rated by two numbers like 190-195. I have tested two thermostats in a pot of boiling water. One was a stock AC Delco 190 and one was a fail-safe 190. They both started opening at 190. The fail-safe was fully open at 196 and the AC Delco took until 210 to be fully open. The fail-safe adapts faster. Dan

Cruisinfanatic

250 is VERY hot and you should be shutting it off at that temp
Take the radiator out and thoroughly clean the fins and replace the thermostat

kael

Also check between the radiator and A/C condensor (in front of radiator). All kinds of junk can accumulate in there and impact cooling.

Cruisinfanatic

Well if the radiator is out, there won't be junk there anymore

KMS88Cal#16

When you have the radiator out to clean it, I would check the tanks for any leaks or seepage first and not waste your time on cleaning a bad radiator. I would use a vacuum/ air compressor to clean ac condenser also. It could be plugged. Be careful not to bend the cooling fins. I would cover your engine if you use a compressor to blow it out. I wouldn’t have believed all of the fine particles than came out of mine with only 57,000 miles on it. Kevin

ctmccloskey

You can clean the radiator and condenser with some Coil Cleaner. Coil Cleaner is available at Home Depot or Amazon and is made to clean the coils on your Home AC system. I used the spray cleaner I use when welding aluminum to remove all the corrosion down to the bare metal. Either way the radiator will transfer heat better If you have a clean radiator.

When you fill your radiator be sure not to use too much anti-freeze. Here in NOVA I use 70% water 30% anti-freeze in my radiators as it provides enough protection for this area. It is better for cooling to have less anti-freeze and more water. I might also suggest a bottle or two of the RED LINE Water Wetter to be able to run a bit cooler.

If your Corvette is running 250* when running you DO have a problem. Is your radiator cap old? The radiator cap needs to be replaced about every ten years along with the coolant and hoses in a pressurized system. The 16 pound radiator cap ensures that your engine is able to see 260* without boiling over.

One cause of engines running temperatures like you are reporting is having a plugged or partially plugged Catalytic Converter. If you pull the Oxygen sensor you should still have most of the air going out the exhaust but roughly 5% will come out of the O2 hole. If you have a lot of air blowing out the O2 hole then it might indicate a plugged catalytic.

The rubber spoiler that goes under the nose of the Corvette is very important. If it is missing or broken then you would get a hotter engine.

The EGR is important for a normal L98 engine running properly. If your EGR is not working it pushes the combustion chambers temperature up into the "detonation zone". A faulty EGR will require you to run higher Octane fuel to prevent pinging or detonation. A simple test is to hook a handheld vacuum pump to the EGR and pump up the vacuum. The EGR diaphragm will move and it will rise and drop based on the vacuum. The EGR is controlled by the EGR Vacuum Solenoid which is bolted to the thermostat housing on my 1988 C4. There is a wire harness that attaches to the solenoid that uses a PWM signal from the ECM. Be sure that it is all connected according to the decal under the hood showing the emissions system.

Have you checked the engine's timing to be sure it is where it should be?