My 91 rs 305 tbi is giving me fits. I have not been driving it much in the last year, but it a a problem I cant get to go away.
First, radiator was replaced last summer, as was the thermostat to a 180- radiator tank cracked and was leaking. This is the first time I ever saw the temp gauge go over half way.
Now, when I crank up and leave the house, around the 7 mile mark, my temp keeps climbing and climbing getting to the 240-250 range before dropping back down, then the rest of the trip will keep the needle about the proper place and it never goes high again. It does not always do this, but scares the crap out of me as I watch it climb just waiting for the steam to hit the windshield.
So, I am figuring faulty thermostat that is sticking closed and after it cycles open once, it is good. Change the thermostat to a 160 failsafe and figure my problem is solved- not, same thing.
I cannot remember if for certain I changed the water pump shortly before the radiator problem, but I believe I did. I had radiator problems with this and my tahoe at the same time and havnt drove the camaro much since that time because I was building a house, they were and still are doing a lot of major road construction around me and I also had another work car.

I am thoroughly stumped on this one. I thought maybe the gauge or sender was just acting screwey, but I put a digital temp probe in the radiator and it was almost spot on to what the gauge said. Even with the 160 in it right now, it will sit and idle around the 200-210 (dictated by the elec fan mostly)mark, as per the dash gauge and my probe.

Thought maybe I have the wrong waterpump- reverse flow, but not sure how to tell. Every smallblock I have now is set up for serpentine and the waterpumps all look almost the same to me.
Upper rad hose is getting hot so.water is flowing thru it.
Tried burping the system several different times thinking maybe air was somehow trapped in there, but never any headway.

Anyone have any ideas?
If I did change the waterpump( and I am fairly certain I did) it would have been a new- not rebuilt autozone unit. Could it be faulty (bad imp) or the wrong one? How to tell?

 

Do you have a coolant bypass?

 

Guess you are referring to the vacuum heter valve under the hood?
Car is bone stock under the hood, everything as it came originally.

 

Got an air dam?
My car will do that when I dont have good air flow.

 

Yes, have an air dam, but it is not an airflow problem. While the car is moving more than enough cold air is flowing over the rad, it was under 30 degrees the last time I drove it and watched the temp gauge climb.

 

Anyone?

 

Your cooling system may not be pressurizing, do you have a leak or a worn radiator cap?
Also when my radiator was getting old my car started to run hot (240'F) even with a straight belt driven fan beating air all the time. It was getting clogged up with solder bloom. I believe the heater core can get the same way and if you don't have a good amount of bypass coolant you can have all kinds of weird cooling problems.

 

Fairly sure the system is pressurizing, I have a cap with the flip lever to relieve pressure and after it warms up, it definately has pressure.
Radiator is new last summer, heater core new a few months before the radiator.

I did realize that the heater control valve was stuck and would not let coolant circulate thru the heater core, changed it yesterday. Dont know how this would affect my problem, but at least I will have a working heater now. Will probably drive it tomorrow and see how it does.

 

ok i have the same problem and i have a bypassed and cracked heater core, should i replace this and go from there? i have an 88 rs with a 350 carb

 

You have to have a coolant bypass, the bypass doesn't have to go through the heater core (but it helps so you can turn on the heat to help regulate temp).
Is your thermostat fully opening?
I just cooked several used thermostats in pot of water last night and one I had been useing last summer only opened between 1/3 and half way.

 

Are you losing coolant? It could be a blown head gasket.

 

Not losing any coolant and no blown headgaskets/ cracked heads.
All plumbing under hood and entire car is exactly the way it left the assembly line.

 

Changed the heater valve because it was stuck- no flow to heater core and all is fine now. Guess the heater valve was also blocking coolant flow?

 

this sounds similar to my problem