Hey guys I have a 1991 Camaro that originally came with the v6 but was soon after swapped to a 350 tbi. The swap was not done by me and I have no idea what the motors like inside but they said it was rebuilt by jasper engines. Also it has dual magnifier exhausts. My car was parked for the winter and I just took it out. I had it idling in my driveway. It idled for about 15 minutes well I was inside. I drive it some before I left it to idle. I came outside and their was smoke everywhere, actually steam everywhere. And I opened the hood to see that my radiator overflow cap was gone (on the ground) and the fluid was boiling out everywhere onto the motor, my gauge said the car was not too hot but I don't trust the gauge because sometimes it goes crazy and bounces from top to bottom. But anyway I came outside and the fluid was boiling (a lot) and their was steam and water pouring out the overflow. The actual radiator cap was still on but whistling from the pressure release valve. I'm just puzzled and wanted to see if anyone had any explanation. Also when it was boiling the water was way above the full hot mark. Thanks. Blake

Try a new cap first.

Would the cap being faulty cause the fluid to boil or just the pressure release valve to mis function?

The pressure of the cap is what keeps the fluid from boiling.

So if the cap o my overflow cap was off would that cause it to boil also? Because I'm pretty sure that dumb plastic cap is pretty much stripped out

He's not talking about the plastic cap on the bottle; he's talking about the radiator cap.

Replace it.

Yeah I know. I was just wondering if the plastic radiator cap would have any effect because it doesn't even screw on, it's stripped out. It just sits on there

For the overflow tank

The radiator cap is not plastic.

If it is, you need a new one anyway; it's garbage from day one.

The recovery bottle cap IS plastic, and that's OK. Leave it alone. Don't worry about it, stripped or no.

We're not talking about that. We're talking about the RADIATOR cap.

Replace it.

Yes it does. You can pick up a 16lb cap pretty cheap or you can upgrade to a thermocap like I did. https://www.thirdgen.org/forums/cool...cap-gauge.html

A bad head gasket can do the samething, replace radiator cap first. Overflow cap doesnt matter it just keeps debris out.

A little confusion here. There are two caps. Radiator cap and overflow cap. Some GM radiator caps are plastic. I was talking about the radiator cap on my last post.