Bought a 93 LT1 that recently had a new water pump installed. Car ran cool for 10 days then overheated. I changed the thermostat and the car seemed to be fine. Two weeks later it's getting hot again, but not every day. Anyone know of something I'm missing?

 

Have you cleaned the debris out of the front of the radiator?

 

Can you be a little more specific with details?

When you say overheated, exactly what temp was it?

Who changed the water pump and thermostat?
Was the system purged of air afterwards?

Try this:

With the engine cold, open the surge tank cap and ensure the coolant is full. Remove the air cleaner duct system and locate the two bleeds one at the throttle body and the other at the thermostat housing. Tuck a rag under the throttle body bleed screw and open it until you have a free flow of coolant. Be sure to capture all of it in the rag. You don't want to get coolant on the opti-spark distributor. Then go over to the thermostat bleed tuck in some rags and open it until a free flow of fluid no air. Re-top off the coolant in the surge tank. Put the air clearner back on. Leave the surge tank cap off and start the engine monitor the temps as it comes up to temperature. At about 185 or so the thermostat should open and you should see flow through the surge tank. Re-top it off if necessary and close the cap.

See if that doesn't solve the problem.

Also inspect all your hoses for soft spots. Look in the intake under the nose for debris and also look at the passenger side of the radiator housing you'll see an opening between the radiator and condensor. Use a flash light and look for debris. If there is any inbetween you can get a couple foot long piece of PVC pipe cut a elongate angle on one end and tape the other end to the vacuum cleaner hose. This is just wide enough to fit in the opening and allow you to remove and debris. Be very careful only drag across toward you but not touch the radiator fins. Push it to the far side away from the fins the drag back across nearly touching.

I should add: normal temps while at cruise will be from 196 - 205 depending on the time of year. In stop and go traffic they may be from 220-231 or so, you should see both fans kick on at 228. It should be able to hold it stead around the 220's in hot stop & go. Once you get moving again the temps should come back down to around 205-212. Or less depending on the conditions.

 

Mine had similar problems when I got it, just needed a new radiator cap. I think I would try that, its cheep and easy to do.

 

Thanks,
Car is running 265+ on highway. But not every day. Dealer changed the pump and I changed the stat. I'll bleed the system and check for debris. Thanks again for your help.
GW