vettin_it

My buddys 94 z28 has been doin this for a while. basically he sums it up as he drives for about 10 minutes fine then the temp gauge reads that its overheating. soon after he says that the engine has a hard time running, like the computer is trying to shut it down? It's not boiling over and hes positive its not overheating.

Dealership said its the instrument/gauge panel that needs to be replaced for $700......I call BS on that though..

Any ideas?

Green96Z

If you're absolutely sure it isn't overheating, it might be the temp gauge sensor. There are 2 temp sensors: one in the water pump for the PCM, and one in the driver side cylinder head for the temp gauge. The one in the head goes directly to the gauge and not through the PCM, so it could be your problem.

vettin_it

But if that sensor isnt going to the computer then why would it be trying to shutdown?

Injuneer

The PCM does not shut down the engine on high temp.

How do you know the engine it NOT overheating? Have you scanned the PCM to observe the coolant temp gauge readings?

izzyz28

Sounds like he's got a bunch of air in the system.

red 95 z28 lt1

if it was the one sensor for the pcm then the fans would come on as well, are the fans running at high speed when this happens?

LaredoZ28

I agree with the air. I had the same problem with mine till i got all the air out.

JP95ZM6

Air, or failed coolant pump, or stat stuck closed can all make it tough to diagnose overheating.

LaredoZ28

^^Very true. I put a new stat in mine filled it back up with coolant blead the air properly and it fixed my problem. I had put a new water pump on it like a month b4 so i know it wasnt the pump.

vettin_it

thanks for the help guys. These are things that I had suggested but he insists its all fine and not overheating. maybe with some people to back me up he will let me check this stuff out

Injuneer

Again.... hook up a scanner.... can't argue with what it shows as the coolant temp sensor reading.

LaredoZ28

Yes I forgot to mention hook a scanner up to it so you can see what temp the pcm is reading. Good suggestion Injuneer.