Hi all, I have been scratching my head at this one for a while and figured someone here might have some knowledge on this. I have a bare stock 1991 camaro Rs with the tbi 5.0 in it, and I am having some bad cooling issues with it. The cooling fan wont come on until the coolant is boiling, and the temp guage is pointing to just before the red marks. At this point the fan kicks on and cools the car to the mark between the red marks and 220 and then turns off. I regularly commute in stop and go traffic and it is killing my car! My air dam is there, but is bent back to a 90* angle, the thermostat is new, and i just installed a new fan relay. What else is there to look at? Thanks!

 

There is a coolant sensor that turns the fan on and off. Its located on the passenger side head on my 86.
They are about $15-20 depending on the one you need for your style.
Should be able to pick one up at any good parts store.

 

mine does the same thing and I replaced all sensors and thermostat. cant figure it out???

 

A weak block ground will affect all things electrical. Clean up the grounds and battery terminal.....it's an often over looked thing. Everybody looks at power, never grounds.

 

I replaced everything I could, the relay on the firewall, the intake coolant temp sensor, the radiator fan coolant switch on the right cylinder head. The fan has power, the fan turns on when I turn the a/c on. Etc. I took the relay out and jumped the power to the wire that activate the fan and it works. Nothing is working still goes into the read.

 

I replaced everything I could, the relay on the firewall, the intake coolant temp sensor, the radiator fan coolant switch on the right cylinder head. The fan has power, the fan turns on when I turn the a/c on. Etc. I took the relay out and jumped the power to the wire that activate the fan and it works. Nothing is working still goes into the red. I don't know what to do anymore

 

Did you check the temp with a laser thermometer light ??(good investment) I bought one from Harbor Freight and found that my car was 25* cooler then the gauge was showing.

 

No I did not. But I put fresh coolant replaced all senora, thermostat with a 160 degree one, and the relay for the fan. But the fan still isn't turning on when it's apost to. The car almost hits the red on the gauge and then I turn the car off. I'm buying an after market fan for it. I'm done trying to figure it out.

 

The factory fan switch DOESN'T EVEN COME ON until about 235°. Then it turns off at about 210°

Meaning, the factory engineers (not that I'm saying those guys actually "know" what their designs are supposed to do when operating, but whatevz) think that anything up to 235° is perfectly fine; and, anything below 210° is TOO COOL.

What temp is the engine ACTUALLY REACHING? What makes you think it's "boiling"? If the reason you think it's "overheating" is that it's spewing, have you tried a new radiator cap?