okay Guyz i need help. I got my 1994 Camaro Z28. Stock 350 LT1. Couple weeks back my water pump went bad, it was leaking from that little hole on the bottom. My dad and friend replaced the water pump. After we took it for a test ride, we went to Auto Zone, then went to Kragens cuz they have a Performance asile there. After we drove more then to Taco Bell, then we realised it was over heating. Water was boling from the raditaot and resvoir tank. We were like WTF? The water pump and hoses were all good, i even bought a new raditaor cap that night. We realised the fan wasnt on, we check the fuses and relays they where good. I didnt use the Z28 for like 2 weeks till we checked to see whats the problem. We found out when we connect the Maf Sensor. The fans turn off, but when we unplug it they turn back on. but in doing so the Check Light comes on. So ive been using the car with the maf sensor dissconnected. So the Check Engine Light comes on. What could be the problem??

 

It sounds like the temp sensor for the ECM or the wiring from it to the ECM may be bad. The temp sensor for the ECM is the sensor that is located on the water pump. But I would scan the car and see what the ECM thinks the temp is.

 

We went to AutoZone, so i could scan to see if it was giving me any codes. But the thing would not fit my car so it could scan. So you think its the wiring?

 

Not neccessarily the wiring, but the water temp sensor for the ECM, Or come to think of it it could be air in the system too, I would bleed the system (bleeder on the heater hose and on the thermostat housing). But if the bleeding doesnt correct some of it I would check the sensor.

The 94s have the older OBD 1 socket. It would be best to get a real time scanner that tells you exactly what the ECM is seeing from the sensors.

 

Yea I have OBD1, Autozone only had the scaner for the OBD2. Im gonna have my boy check it out, hes the mechanic. I havent used the Z much its been parked for weeks now, since skoo is out. But it runs hella good. But i need to fix the problem cuz the Check Engine Light is on, its annoying.

 

When the SES light is on, the fans are turned on by default if my memory serves, getting the light to go off (in this case by plugging the MAF back in) should turn the fans off, that's working properly I believe.

Did you verify that when getting up to overheating temps that the fans actually weren't running? It could have just been air in the system causing it to overheat regardless of fan operation if you guys didn't bleed the system after the WP swap... I'm assuming it's not this since you seem to indicate that with the fans forced on it doesn't overheat, but just to cover that base...

If you've verified that when reaching temps they should be on at that they aren't, then you need to look at why. Since they come on with the check engine light it's obviously not their wiring directy, it's got to be something related to them getting the order to turn on from the ECM. Which mainly means wiring/sensors the ECM uses to know engine temps, as others above said the ECM's temp sensor. If it's thinks the engine is colder than it is (regardless of dash temp gauge readings) the ECM won't turn the fans on. Just about gotta be related to the ECM not reading the temps right I would think since they do come on w/ the SES light. I'm not one of the real LT1 gurus here though, hopefully more help will be along shortly if it's something more in depth...

This link has some info on the cooling system: http://shbox.com/1/4th_gen_tech2.html#cooling
If you have a decent digital volt meter you can do some testing of the sensor with this info: http://shbox.com/1/4th_gen_tech2.html#ect

 

Exactly (you explained it better),

The sensor I mentioned on the water pump tells the ECM what temperature the water in the motor is, this is only for the ECM, the gauge sensor is on the driver side head and is gauge only. The ECM is told via its program when to turn on each fan by preset temperature. If the temperature is not read by the ECMs sensor (on the water pump) then the fans will not come on until then.

You verified the fans and their appropriate system working by the default "unplugging the MAF". which puts the ECM into a different mode and it just keeps them on because it senses a problem.

With a scanner you can see what the ECM is reading from the sensor and know wether the temp has been met to turn the fans on.

I would bleed the system and then go from there.

 

My friend didnt bleed any system. The engine did get extreamly hot, it was over loading the water in the water resovoir. That was the only place it was gushing out water. When we turned off the car, you could hear it boling. yea when we connect the maf back up, the Service Enigne Light turns off, but that causes my fans to turn off. Will the primary fan, the secondary only turns on when the ac is on. On the sensor from the water pump my friend put water gasket silicon was that right?

 

ok, have you tried bleeding the air out of the cooling system? that and a bad cap are tied for the #1 reason for boil over

 

Check the coolant level while the car is cold. Take the radiator cap off and see if it is low.

 

Yea i bought a new radiator cap. I dont think there air in the system. The coolant is fine when the car is cold. Its not leaking its the fan problems.

 

Its gonna be for sure i bealive the sensor on the water pump.

 

I've had a bad sensor in my water pump and even without the fans on the car would only get hot if i was sitting still in traffic for long periods of time. If you were stopped for a long time and it overheated then, get the replacement sensor from gmpartsdirect.com.

Also sounds like you've got air in your coolent system. Look at your manual it tells you how to get it out.

Try both of those and you should have it fixed.

 

If you didn't bleed it, then there IS air in it.
Bleed it PROPERLY FIRST, then come back if the fans don't work properly. (I'd bet they do once you get it bled properly).

Why not start with the easy, free fixes -you know; the ones that 6 people have already told you will fix your trouble, BEFORE dumping more time and money than necessary into this?
And if you're not going to listen to the advice given, then why even post a question?

 

yeah, I haven't said any more because he never tried to bleed it, so, i gave up until he does