a while back i had a 160c thermostat installed in my '79 (400sbc). when i'd start her the temp would reach 220 then settle back down to 160/170 within a short time, so it worked pretty good. Recently, when i start her up, the temp will go to 260 and then fall back down to 220 and stay there. Only after about 40 minutes of driving will the needle fall below that to about 190 and in traffic goes back up to 220/230. can anybody please tell me whats going on here? i thought my temp problems were over!

Don't take this to heart, but are you sure that your gauge is accurate?


my .02 cents

Chris

Sometimes get this since the temp gauge sensor is in the head, heats up before the thermostat sees the heat. Usually though it's a junk thermostat - or the radiator is not flowing well.

isn't that too low of a thermostat? i have always heard to run the 195. i run that now and my new engine with my electric fan never gets over 205.

well i was using a 180 for a while but it got to be running too hot so i switched to the 160 about 2 months ago and this worked great until just recently. As for the gauge working properly, its a valid concern as the sender looks kinda beat but i'm not sure where to get hold of a new one. But then again, when the gauge is reading over 220, its blowing some pretty hot air. I have a feeling it could be a flow problem. Will a radiator flush rule that out?

A thermostat, by itself, has no effect on the cooling of your engine. It is just a small piece of metal with a temperature-controlled spring whose job is done once the temp reaches its threshold value. The function of the thermostat is to prevent the coolant from circulating until the temperature is high enough to cause it to open. Once the coolant is circulating, the radiator has the job of dissipating heat. The engine will run at whichever temperature is higher, the threshold value of the thermostat or the equilibration temp that the cooling system is capable of maintaining. If the engine started running cooler after you put in the 160* stat, it is probably because the outside pemps were getting lower and you were starting to use the heater more.

If you are having problems with the cooling system, a do it yourself flush may help, but if it is serious, you may need to take it to a professional. Be aware that if the radiator is full of crud, so is the block.

There are a number of things you can check to see if your cooling system is doing its job before you start to flush. Make sure the coolant is full and you are not losing any from leakage. Check the hoses for leaks, and (with the engine off and cool) check the lower hose to see if the internal spring is in place. If it has rotted away, the hose may be collapsing from suction of the water pump and limiting coolant flow. Check the fan belt for proper tension and see that there is no glazing that would make it slip. If there is a clutch fan, be sure the clutch is not shot. Use a shroud and make sure it is sealing to the rad. Check for airflow through the radiator. Sometimes you can get crud building up between the fins of the radiator or the condenser if you have ac. Check for build-up between the radiator and the condenser. Although it is not too much of a problem for Camaros, Corvettes are notorious for overheating problems due to leaves, candy wrappers, assorted road debris, etc. getting between the radiator and condenser (because of the angle they sit at in the nose). If the water pump has been on the car for a while, the vanes on the impeller may be rotting away and the flow will be less than necessary for good cooling. Most of these are quick and easy to check before you want to try the flush routine. Good luck.

hey thanks i'll check out all the stuff you just mentioned before i flush it. Cheers

Sean

First, have someone check the radiator cap to make sure that it is good. My dad chased a overheating problem on a 69 Javelin. The dealer changed everything but the cap. The son of the owner of the place I worked at knew in a second what the problem was. Yanked the cap off, put it on the tester (it looks like an old hand tire pump with a gauge on it and a bunch of adaptors to fit all the different caps and radiators) and found the cap was shot. All Auto Zone and Advance Auto Parts stores have the pressure tester I'm taling about. Also have them pressure check the radiator while you're there. The engine won't cool if the coolant isn't under pressure due to a leak or a bad cap.

Testing a thermostat: I allways test a thermostat before I install it as I have found top name thermostats (like Rober Shaw) that were bad. To test it, put it in a pan of cold water with a thermometer (like a candy thermometer). Slowly bring it to a boil while watching both the thermometer and the thermostat. It be should open completly near the operating temperature.

Do you have a fan shroud? If not, get one. Is it a clutch fan? Make sure that when the engine is warm that it is rotating at full speed.

I agree with Cardinal. Do the simplest things 1st. If the coolant level is full, have the cap AND the system pressure checked before you do anything. Losing pressure in the cooling system due to a bad cap or a leak somewhere else will wreak havoc on a cooling system and sometimes make it difficult to chase a problem. I've seen it a hundred times also, people will spend small fortunes trying to fix a overheating problem, when all they needed was a radiator cap. If you find that there's no leaks and the cap is good and still have problems, then it's time to look at the other things already mentioned.

If you have billet aftermarket pulleys, you better check to ensure they are the correct diameter. Underdrive pulleys without the proper high output waterpump and oversized aluminum radiator will cause the motor to run hot all the time.

Like they said, check the easy stuff first.

I had the same issue....
I changed the thermostat, I changed the fan clutch, then, I looked in the radiator, saw white crusty stuff and decided to flush it...

Flushing seemed to help but the radiator started to leak a month later. A new aluminum radiator (autozone- $105) seems to have been what I needed all along.