I have a 95 z28 convertible. I was driving to kansas for a job and soon as I get in the state start losing coolant. Limp it around, Radiator and hoses were all new, change the radiator,which was still under warranty.

All seems well but now the fans wont turn on.
Connections are tight.
Replaced the temp sending unit in the water pump, still wont work
checked fuse, fine.
changed out modules and that didnt work

what else could it be??? broken wire somewhere maybe?

 

Also a while back my heater core went out and I had to bypass that, could that some how be related? It has ran a while just fine without it.

 

The power to the fans does not go through the fuse box. It is supplied directly from the red "+" distribution box on the passenger inner fender, and protected by a fusible link. The fuse box fuse only protects the "signal" side of the relay.

See Shoebox's diagram. You should have the 3 relay "late production" setup.

http://shbox.com/1/fan_schematic_1995.jpg

Is the indicated coolant temp going above 226*F, where the fans switch on low speed? Do the fans come on if you turn the A/C on?

 

Indicated temp is going well above that, tested it this afternoon, and fans are NOT coming on with the AC turned on. I am wondering if the guage temp sender is working correctly, but that still wouldnt explain all of the issues.
How possible is it that the fusable link blew?

 

It's a fuse. It's purpose is to protect the electrical circuit. If there was excessive current draw it's blown. Check it. You either have 12V at the load side of the relay or you don't.

 

I noticed this evening that after the engine supposedly got so hot the radiator hoses were not very warm at all, and the coolant was not very warm at all, warm enough to touch, I'd say 100-110 degrees, also when the car gets hot if cools down in minutes. This is why I think the gauge may be wrong.

 

I'll check that out in the morning.

 

You need to see what the coolant temp sensor in the water pump is reading, or at least how the PCM is reading it. You can do that using the free 94/95 OBD-1 software you can download from the "sticky" on the "Computer Diagnostics and Programming" forum.

It is possible for the engine to be very hot, and the coolant hoses to be cool, if your t/stat is stuck closed.

 

You can also check the sensors using Shoebox's guide:

4th Gen LT1 F-body Tech Articles

 

You should also read the cooling system info on my website. There you will find how can check fan capability by shorting pins in the DLC.

 

I've read all of that before, and read it again last night. Refreshed myself quite a bit (once again shoebox thanks for the awesome info on your page.) again.

Unfortunately I am not at home, but on the road for work, and am having to change motels again tomorrow to keep up with the pipeline we're working on. So I finally threw in the towel and took it down the street to a midas. I hate declaring defeat on something so seemingly easy to fix, but I am tired of working on the car in either an Autozone parking lot or Motel 8 parking lot... in snow... in below freezing temps.

 

SO I talked to Midas and they are saying that the waterpump (which is a few months old) isn't pumping correctly and that it or either the cam rod is broken. So they are wanting to take the waterpump off...charging only $278... which seems very cheap.

But how the hell does that have anything to do with the fans? Gotta wait until the techs are in for that to be explained.

 

"cam rod"??????

Did they indicate the drive gear for the pump (which is driven off the back of the cam sprocket) was not working?

If the pump isn't working, the sensor in the pump may not be getting as hot as the sensor in the head. That could be the cause of the fans not coming on. Scanning the PCM to see what the temp sensor in the water pump is indicating would clear things up.

 

Just an update. They showed me the coupler and it was heavily worn on one side, not sure it was that big a deal but certainly would have been later on. Car still was over heating and finally they figured out the impeller in the water pump had somehow come off the shaft inside the waterpump, which was less than 6 months old and from Advanced.