LT1 Overheating, can't find problem?!
 

Okay, my 95 Formula has been overheating and I can't find the problem. I'll drive it for 15-20 minutes after letting it idle for 5-8 minutes on the driveway. It'll creep up to 210 and then all hell breaks loose and it rockets to 240-250 and the coolant boils away and I shut it off. I've been fiddling with it for the last month and I'm pissed off :bang: I flushed the radiator, flushed the block 5 times, tested the thermostat (works) manually wired the radiator fans so I turn them on with a switch, took the front plate off the water pump and it turns when the engine fires up, no coolant leaks anywhere, the rear steam pipe is on correctly on both heads, replaced my main two coolant hoses even. WHAT THE ****! I let it idle on the driveway with the fans going and it slowly creeps up to 240. I raised the front nose all the way up and bled any air bubbles that might be trapped and pumped out all air pockets and tested the pressure and it all holds pressure. ***I feel the engine and it feels very hot, but I touch the radiator and hoses and they are ICE COLD*** why is that? Water pump works fine. :mad:

stuck thermostat?


did you use the right kind?

Test the thermostat by boiling some water and drop it in there to watch it open. If it opens, its fine. If it stays closed, ya found your culprit.

You say the coolant boils away, so are you losing coolant? Sounds like a leak somewhere. Have you replaced the radiator cap? Check all the hoses for damage.

First I'll state the obvious: coolant is not flowing through your radiator.

Your thermostat should open at 180 degrees I believe. My Corvette typically runs between 208-213 degrees, and the radiator fans come on at 225 and 230 as far as I know. This will only happen in traffic, regular driving never goes above 215.

If you haven't tried getting a new thermostat, that is the first step. They're cheap, so you might as well get a new one to see if that fixes the problem. Just go with an OEM 180 degree t-stat. You can get them at any auto parts store; try that a.s.a.p. and see if it works.

- Vinnie

Yes I have the correct gen II LT1 thermostat in there. I put it in a pot of boiling water and it opened just fine

Why would it not be flowing? There's no visible leaks anywhere under the hood or under the car, and the water pump IS turning... I'm lost. I removed the radiator and flushed it and power sprayed the inside the remove any gunk out if any. I tested the thermostat in a pot of boiling water and it opened just fine. I have the radiator fans manually wired, I turn them on at about 170 degrees and they stay on. Nothing is adding up.

I haven't replaced the radiator cap. All the hoses are brand new, I just put them on and they're all on tightly. No leaks or damage on any of them

I've tested the thermostat in a pot of boiling water. It opened like a charm. I tested it about 3 weeks before the overheating problem started getting bad.

Try bleeding the system. Air in the passages could cause your problem.

check/replace your guage sending unit (the one in the drivers side cylinder head) there are 2 the other sending unit in the front of the waterpump is for the pcm for calculations.
iam willing to bet your sending unit has took a dump and you are freaking, we've all been there. if you've verified that you are pumping coolant into and out of the radiator and your fans are working there is nothing else i think it could be

Does it smoke at all, like a cracked head and that's where you are losing coolant? Mabye a bad head gasket and you can't see where the leak is?

Since its obvious you dont have coolant flow through your rad hoses, Id say the water pumps starting to go out or maybe(unlikely unless its been sitting for awhile) the fins in the radiator are clogged too.

Since the upper hose is right where the thermostat elbow meets the rad hose, id be willing to say thermostat or waterpump.

I brought the front end of the car as high as I could get it, and opened the bleeder valve and pumped the radiator, there is no air bubbles or pockets anywhere in the cooling system. I even drained the block 4 times with coolant.

I'll try that thanks. But what would cause the engine to feel piping hot, yet the radiator and hoses are ice cold??

I replaced the passenger head gasket last November. I can't tell if it's smoking because it is -7 degrees out right now and all cars have steam coming out the tail pipe when it's this cold. It's impossible to tell what is steam and what is smoke

I'm starting to lean with this guy a little bit. :nod: more or less WP rather T-stat, since you said you tested it already.

The water pump is working, I took the front plate off and fired up the engine and it is turning just fine when the engine is running. I also power washed the sh** outta the radiator at the shop to get any foreign debris out of the inside. It's squeaky clean. But the car still overheats.

Since it pulls coolant, motor gets hot and overheats, but doesn't seem like its putting it back hot, or not at all, I'm gonna point my finger somewhere in the return portion of the coolant cycle. I just don't know enough or just sounded like an idiot. :confused:

For how intricately the cooling system is, the procedure is simple. Coolant simply circulates throught the system to keep everything cool. Since the radiator hose is cold, your not getting complete circulation. So if you say your waterpump is working then you definatly have a clog somewhere, or something. Even though the waterpump appears to be working and usually you loose the WP gasket before the pump actually fails, I wouldnt count it out as the culprit.

But I would start with the cold hose and put some time in.