Hi Guys,
This is my first post here. I am hoping for some help or advise about my Camaro's cooling problem.
I have had this problem since buying the car just over a year ago, have been trouble shooting it and trying to pin down the issue for awhile now.
Basically the car runs fine until I take it out on the highway at around 75 mph the engine heat climbs and does not stop, eventually it will peg out and overheat. By setting my heater fan to hot and blasting on the heat it cools the engine right down. Same is true if I drop the speed down to 70 mph or less.
The electric fan is turning on (I already replaced the electric motor hoping it was defective), I have done a DIY radiator flush, replaced the thermostat (even ran it without a thermostat for awhile), replaced the radiator cap, and the cooling system does not leak.
The car will heat up like normal while driving at speeds of 70 mph or less, then my fan kicks on and it cools right down, but at speeds of 70+mph it never cools down. I think the car runs a little hot all the time. What is the average temp for a V6 Camaro to be running in normal circumstances?
Anyway just can't figure this out, should I have the radiator flushed at a radiator shop or should I just replace it? Could it be the water pump not keeping up at higher speeds (and RPMs)? Is the heater core blocked and causing the heat (I don't think it is this as the heater blows VERY hot when I turn it on to cool the engine down)? I've even thought the catalytic converter might be plugged causing exhaust restrictions and heat to build up at higher speeds (RPMs). I had a bad knocking sound (like rocks rattling around in it) coming from the catalytic converter awhile back then it stopped. But the car seems a little sluggish since this happened.
Any help or advice would be much appreciated.

 

Is the air dam under the radiator missing?

 

First thing that comes to mind it air in your block. You need to purge the air from your block in order to get proper cooling. The radiator being full really does not matter if there is air trapped. What happens is this air gets to the water pump and causes the pump to cavitate and once that happens there is no water flow. Turning on the heater helps to move the air away from the pump, that also explains why you dont get much heat out of the heater. The 3.8L engine has a bleeder screw on the top of the thermostat housing, I dont remember where the one is for the 3.4L

Do you use water only or antifreeze? If water only then the issue is most likely steam pressure causing air gaps and the same issue as the first paragraph.

The plastic air dam under the car helps push air up into the radiator, at all speeds, you need it if you dont have one or if yours is broken you will have issues.

Check out what I said and see if that helps.

Massey

 

Thanks for the tips.
I think you may be on to something with the air dam idea. My heater does blow SUPER HOT. I've taken a couple of trips this summer and had to turn the heat on full blast on the highways and cooked my feet the whole way.
But my car IS missing the air dam under the front end. Original owner had to replace the front end after it was backed into in a parking lot. I noticed he did not replace the air dam. I was wondering about that myself, had also thought my front end cover might be restricting air flow, but then I remembered that it would heat up even before I put the cover on it.
Gonna go with the air dam idea. Gotta find one for sale now. I'll repost with the results as soon as possible.
Thanks for the help guys.

 

Wrecking yards usually only want a couple of $$$ for one. I think the last time I checked they said $10 in my area. Also make sure that all the other plastic shielding is in place as well, it does not do much but it does keep the water out of where water does not need to be, like your lights.

Massey