1989 IROC-Z
5.7L
700R4
Dual fan

Alright, I've been researching this issue for the last hour or so and I've yet to draw anything conclusive.

Ever since the heater core replacement was completed, the car has been running hot. At stop lights and even in traffic, the heat would start to blow cold and the engine would rapidly overheat. After idling it with the radiator cap off and filling it in an effort to get the air out of the system, I have yet to have that problem again.

It now just seems like it runs way, way too hot. The left fan doesn't come on until 240~ degrees and the right fan doesn't come on at all, even if the A/C on (it's not charged, if that makes a difference.) From what I understand, the two fans are independent of one another and the right one shouldn't affect the operation of the left.

From a couple of things I've read, people say it's normal for the engine to get this hot before the fan comes on but this doesn't seem right. I know it was designed to run hot but I'd like to make sure before I put my mind at ease about it.

Any help you guys can offer is greatly appreciated.

 

Couple of things.
Have you checked gauge is actually reading correct engine temp?
What temp ( indicated ) does engine come down to after fan runs?
Is engine using coolant?



There is no gas in the A/c system to operate the pressure switch that signals the fan to run

 

I have not checked the accuracy of the gauge but it has been reading correctly (to my knowledge) until this point. I don't have an infrared thermometer, are there alternatives?

Engine comes down to about 220 before the fan shuts down again.

Yes? I don't have a reason to believe it isn't?

 

If you can borrow a scanner it will show the actual engine temp as being seen by the ECM ( which controls the fan )
which is supplied from a different temp sensor to the gauge

 

Alright, yeah I can do that. Do any auto parts store carry scanners of OBD-I? Or do I need to make some calls?

 

.

 

Did you " burp " air out & top off the rad, & fill over flow jug to the correct line?

 

Yes, yes and yes but I don't think i burped it properly. I ran it without the radiator cap on, topping it off as it dropped down but it would burp coolant out the top and replace it with air again.

This is my first cooling system issue so it's been touch and go.

 

Warm engine , thermo open , heater on.
Run engine at revs ;2000 + ( should see coolant level drop in radiator )
Pour coolant in while holding revs up , replace cap before letting off revs.

 

Tried it and I can't do that, coolant level doesn't go down, it just spits it back out the top of the radiator and onto the battery. Which creates a cavity and more air gets sucked in. What am I missing here?