Overheating Puzzle to Solve

[AstitchINtime]

After about one month of ownership of my 03 nonturbo PT I bought used, it started overheating (bubbling noise, temperature light go on, etc.) in stop-and-go traffic. Changed the thermostat and flushed the radiator. After 1 week it started overheating again.... but the peculiar thing is that even though I filled the reservoir a little above the "add coolant" level (or close to halfway between the minimum and maximum level in the reservoir/overflow), after the last time it overheated, the reservoir/overflow came out with the coolant level topped off (ie. way above the maximum level), just under the opening and bone dry under the radiator cap.

No leaks of anything (no puddles of coolant or water).
No smoke (only steam the last time it overheated).
There is pressure inside the hoses when it overheats and of course it's hot to the touch, but softens when it cools down.
Fan seems to turn on when AC runs - don't know if there is another way to test this --- but if it was the fan, would it make coolant flow in one direction and accumulate in the reservoir/overflow???

Do fail-save thermostats ever lock closed? or only lock open? And with either case, would it explain coolant accumulating in the reservoir?

Thanks much for any input and help.

[Hooligan]

Couple of things come to mind: Air needs to be bled off and you have two fan motor speeds, one for low and one for high speed.

[AstitchINtime]

thanks for your reply. how do you test each fan speed?

[CREWZIN]

When you first turn the car on in the morning, also turn the air conditioning ON. The low speed fan should come on. It comes on every time the air-conditioning is used.It's hard to hear so be careful when looking for it to be on.

Without moving the car, if that's when the car heats/overheats, keep an eye on the temperature guage and if the needle starts to raise over half way, the high speed fan should kick ON. It's very loud, you can't miss the sound. Don't let it overheat but if it gets anywhere near the red and the high speed fan hasn't kicked on then that part of the fan could be burnt out.

You also have to check the relays in the fuse box located in the engine compartment. The High speed relay can be swapped with the horn relay (both the same) to check it out. You know the low speed relay is good IF the fan came on during the first test when you turned the car on.

[AstitchINtime]

Thanks for the helpful info. If it is the relay, how much should I plan to spend to replace it?

I read in other posts about overheating re: "flashing the PCM" and a "TSB" number.... do i have to worry about those? Mine is an '03 non-turbo w/ more than 110k miles.

Thanks again

[CREWZIN]

Never heard of flashing for overheating, but I wouldn't be surprised if there's not a TSB giving hints to the mechanics of what to look for. Seems to be a basic problem with the PT because of failing parts.

I wouldn't worry about the price of a relay, that'll be the least of your problems, probably less than a Big Mac at McDonald's.

What about your timing belt, water pump and non-covered belts? Have they been changed? 100K is what we are recommending to everyone for the change.

[AstitchINtime]

Thanks for reminding me --- when I checked my lower fan earlier this morning and turnedn the AC on, I heard a squealing noise that turned off when I turned the AC back off after a few mins....

I am still waiting on funds and the right mechanic to go into my timing belt. Hopefully soon. Is there a direction connection to any of those you listed to overheating/ does it contribute?

[CREWZIN]

No, no connection from anything to do with the timing belt and overheating.

A cracked block, loss of water and trapped air in the system, bad thermostat all could cause overheating, but the most likely culprit is the high speed fan. Last resort would be a bad PCM (Power Control Module) which controls everything but lots of other things would go wrong before that.

[AstitchINtime]

Thanks again for your tremendous help!

[AstitchINtime]

Originally Posted by CREWZIN

When you first turn the car on in the morning, also turn the air conditioning ON. The low speed fan should come on. It comes on every time the air-conditioning is used.It's hard to hear so be careful when looking for it to be on.

Without moving the car, if that's when the car heats/overheats, keep an eye on the temperature guage and if the needle starts to raise over half way, the high speed fan should kick ON. It's very loud, you can't miss the sound. Don't let it overheat but if it gets anywhere near the red and the high speed fan hasn't kicked on then that part of the fan could be burnt out.

You also have to check the relays in the fuse box located in the engine compartment. The High speed relay can be swapped with the horn relay (both the same) to check it out. You know the low speed relay is good IF the fan came on during the first test when you turned the car on.

Does the high speed fan have a low-hum sound to it compared to the low speed fan (higher pitched hum that comes on and off when the AC is turned on)? With the AC off, after driving car around a little while, I noticed that a low humming sound came on together with the high pitched hum when the temperature needle was close to the middle, then tried it again all while idling and did not notice either sound come one.

Would the high speed relay come one while idling? Does it have a low pitched hum? And if it's a bad relay would it work only sometimes or not at all? Thanks again