Apeiron

My car overheats at idle with a stock 5 blade fan and thermostatic clutch. I haven't checked the clutch to see if the fluid has leaked, which might be the problem, but if that's not it, what should I do? Should I try a stock 7 blade fan, or maybe a steeper pitch aftermarket fan? I don't really want to convert to an electric fan, but that's a possibility too. Even if the clutch has just leaked, should I just replace it, or try something else?

Damon

That fan should be PLENTY for keeping your engine cool. If the viscous clutch is of unknown age, jsut replace it. That sucker should be moving a TON of air when the rad is hot.

If that doesn't help your next part to replace is the water pump (might as well do the stat while you're at it) and them finally the radiator. This is due to the cost of the parts- cheap stuff first and the difficulty of perfectly diagnosing the true cause of the overheat. A bad water pump and a bad rad act very similarly.

Of course, all this assumes that the engine is running acceptably at idle. If you've got mechanical or massive tunign problems this all goes out the window.

Apeiron

The water pump and rad are both new so they're not the problem. It stays cool enough as long as its moving anyway. I'll try heating the clutch with a torch and see if it engages.

Mark A Shields

What about your radiator cap? Replaced it lately? Also if your timing is off or you're running lean then your car will overheat. Make sure you don't have a leak around the thermostat, the loss in pressure won't help.

Apeiron

The cap's new with the rad, no leaks anywhere.

Hellraiser

Do you have a fan shroud? If so check to see if it is damaged in any way, and that its the proper size for your application.
I had a similar problem with a built 350 in my old 86 camaro...
It ran about 230 in the summers in NY, but when i moved to florida i found the car was overheating at idle constantly.
Turned out all i needed was a shroud (id never installed one)
to help move the air straight through the radiator.

Apeiron

Yes it has the correct shroud.

82camaro

If the fan clutch is over 5 years old, replace it. Even if it kicks in when you heat it, it might not be kicking in completely. I had this exact problem with my 91 Jimmy. The fan clutch would kick in and make the fan pull air--just not enough air. With the new clutch (cheapie lifetime from autozone) I can idle with the AC on, in town, when it's really hot out.