Thermostat noisy when open ?

Ok, seems crazy but I have been chasing a noise all week that started after I completed the timing belt service last weekend.

When car is warm I hear a weird noise. Kind of a light metallic rubbing noise. I thought at first it was an idler or the alternator etc. etc.

I was just listening to the car as it warmed up and the noise appears very suddenly. I took the a/c and alt/ps belts off just to see what happened. No change.

If I let the car cool down the noise stops but then suddenly reappears.

This only happens at IDLE. If I even lightly touch the throttle the noise disappears. Is it possible the Thermostat is making the noise as soon as it opens ? And why ? I put a brand new OEM thermostat in when changing waterpump. Used gates kit but with OEM thermostat and OEM waterpump gasket.

As I sit here looking at the original waterpump the only thing I can think if is that the little bypass valve thing is resonating somehow. The noise doesn't really bother me...just want to make sure it's not something that could cause a problem with the timing belt.

Well, whatever it is, I'm beginning to think it was probably always there.

I just never heard it because it was masked by the squeaky a/c idler.

Just another thing to monitor and drive myself crazy over.

That's highly likely. It could also be air in the system? When the T-stat opens up you are hearing air bubbles circulating through the rad? Probably a stretch but worth an investigation.

-mike

Thanks Mike, I will definitely see if I can force some more air out of the system.

It's weird because if I blip the throttle the noise goes away. Once it settles back at idle it then takes a couple of seconds for the noise to come back. Freaks me out because it sounds so much like a rotating/rubbing kind of noise.

If all else fails I'll open the covers back up and see if anything looks / feels funky.