94 TA Overheating and fans wont come on. - PY Online Forums

Jack Blum · #1 07-27-2009, 11:36 PM

OK, I have replaced the temperature sender by the water pump and the sensor on the left side of the block. The fans still wont come on and it just sits there and overheats.

If I unplug the MAF sensor, it stumbles and then the fans both come on and it cools right down. I think it's going into some kind of safe mode. If I plug the MAF back in, the fans will go off and it overheats again.

I am at a total loss as what to replace next. Any ideas, or seen this before?

Also any idea how to properly purge this water system. There are 2 vents on the cooling hoses that I assume you open to purge the air. But is that while running or just off and cold?

I am buying the service manuals but they wont get here for a week or so.

Thanks, Jack.

quicksilver97ta · #2 07-29-2009, 02:16 PM

The PCM turns on the fans depending on what they are set for and it looks at the temp sensor on the water pump to do it. The fans do come on as a trouble mode when you unplug the MAF. I wish I could tell you what to try next but if it was my car I would plug my laptop in and see what the PCM is seeing as far as the temp settings and the temp sensor but of course I'm already set up to do that. How hot does it get? In stock form these cars are set to run 200* easy. Do the fans come on when you turn the A/C on? They should.

I don't know whats proper

but I purge the system with the engine running with rags handy so not to piss on the friggin optispark. I also jack the front of the car way up to get the radiator cap as high as possible, this helps alot. Watch the gauge like a hawk.
Now that you mention it is all this going on at the same time? The sensor at the head can be dry and skyrocket the gauge while the one at the pump will be cooler and not turn on the fan. hth

Jack Blum · #3 07-29-2009, 04:47 PM

Good point about the AC. They do not come on if the AC is on. The only time they seem to come on is by unplugging the MAF.

The other strange part is that the gage is reading OK. Gets up to the red zone and at that point I usually shut it off.

Forgot to mention another thing that happened. It got so hot once that it popped out the water level sensor just under the cap. I snapped it back in and it has not popped out, but I wonder what kind of pressure it took to do that.

I will try getting the front end up and see if I can get any more air out of the system.

Thanks, Jack

Bull · #4 07-31-2009, 10:41 AM

Is it necessary to lift the front of the car up to purge the air? I recently did a tune-up and water pump on my '95 Formula. Afterward, I repeatedly opened the bleeder screw on the upper rad hose (I only saw one bleeder, not two?) while the engine was off, adding more coolant as necessary. I then opened it a few times when the engine was running, and that's it. Even driving in very hot, humid weather the other day, the temp would get up near the red zone but then come right back down when the fans kicked on.

BTW, that tune-up was not fun!

quicksilver97ta · #5 07-31-2009, 12:13 PM

Quote:

Originally Posted by Bull

Is it necessary to lift the front of the car up to purge the air? I recently did a tune-up and water pump on my '95 Formula. Afterward, I repeatedly opened the bleeder screw on the upper rad hose (I only saw one bleeder, not two?) while the engine was off, adding more coolant as necessary. I then opened it a few times when the engine was running, and that's it. Even driving in very hot, humid weather the other day, the temp would get up near the red zone but then come right back down when the fans kicked on.

BTW, that tune-up was not fun!

No, not necessary. There is just alot less air to bleed when you do it that way.

Bull · #6 07-31-2009, 01:39 PM

Ok, thanks for the info!

JOE DEYTON · #7 08-05-2009, 03:45 AM

I have a 94 Z28 had my PCM reprogrammed so the fans come on earlier and added a 160 stat. I think they changed some hoses after 95. The other bleeder I believe was on the heater hose never had a problem with my LT1 overheating. My friends TA had some issues so we wired up a manual fan switch. His is a 93 so a little harder to reprogram. I been through these things a good bit so if anyone needs to know anything let me know.

Jack Blum · #8 08-05-2009, 08:56 PM

Replaced both the temperature and fans switch sensors. Fans seem to come on now when they should. It was probably a bad fan switch sensor.
Only problem I have now is the sensor that detects the water level (just under the top hose on the radiator) keeps popping out, so I will have to get a new one of those.

Thanks all, Jack.

quicksilver97ta · #9 08-06-2009, 09:04 AM

Quote:

Originally Posted by Jack Blum

Replaced both the temperature and fans switch sensors. Fans seem to come on now when they should. It was probably a bad fan switch sensor.
Only problem I have now is the sensor that detects the water level (just under the top hose on the radiator) keeps popping out, so I will have to get a new one of those.

Thanks all, Jack.

Great, glad it's fixed. That coolant level sensor is notorious for going bad anyway so consider yourself ahead to just replace it now. Again, glad it's fixed, these 4th gens are fun to drive when operating properly.