In my 02 Monte 3.4L. I was looking at replacing the radiator cap. I usually use a Stant lever type cap. That way you can make sure no pressure is in the system before you loosen the cap. I noticed the OEM cap had an arrow pointing at the overlow hose. So, I wasn't sure if the radiator needed the OEM cap?

At the parts store, it pulls up a 10331 Stant cap.

 

just get a cap that is good for the pressure that will be created.

 

The Stant cap meets OE spec and has the added feature of a pressure release handle. It will replace your original cap with no problem.

 

I put the new Stant radiator cap on along with a new Stant thermostat, radiator hoses, and I flushed the coolant.

I noticed with the car at operating temp, I can remove the radiator cap with no coolant gushing out. Every other GM car I've had, when the car is at operating temp and you try and remove the radiator cap. Coolant will gush out.

What would cause the coolant NOT to gush out when you remove the radiator cap with the engine at operating temp?

The car doesn't overheat and the coolant needle stays close to the middle of the gauge when at operating temp. The heater works fine.

 

Did you completely bleed the system of air after all of that?

 

There shouldn't be any air. I've opened the two bleeder screws over 10 times since to work out any air.

I've flushed other GM cars that didn't have any bleeder screws at all and didn't have any problems with them.

This is the only car that I noticed doesn't seem to build up coolant pressure. Though it did build up pressure when I put a coolant pressure tester on the radiator and ran the engine. It ended up overpressurizing as the pressure went to 20 lbs before I shut the car off. I don't see how that happened as coolant never gushes out while running with the cap off if there was an over pressure problem. It passed a block leak test.

 

The only thing I can think is that this cap isn't pressurizing the system.

 

I did notice with the cap on, and I squeeze the upper hose. That the fluid will move in/out of the overflow tank.

But on my other GM cars. With the car cold and radiator cap off. Start car and let it warm up to temp. Shortly after the thermostat opens, coolant would start gushing out of the radiator.

Though on the Monte. When it gets to operating temp with the cap off no coolant ever comes out of the radiator. So, it makes me think of something other than the cap.

But maybe it doesn't matter since it doesn't overheat, both radiator hoses get hot, and the heater blows hot.