[blykins]

...pull coolant back out of the expansion tank after shutting the engine off? Does it usually happen a few minutes later when everything starts to cool down?

Since I have put the thermostat in the engine and installed my expansion tank, I have noticed that IMMEDIATELY after shutting the engine off, there is a gurgle for like 2-3 seconds and then it stops. It sounds exactly like a sink drain, right in the area of the expansion tank. It sounds like it's sucking the coolant back in right that second.

The engine runs at 190 all day long....never overheats. Doesn't even spit any coolant out of the expansion tank to the ground.

Do I just have a little trapped air that needs to be bled out of the system?

Tony Radford had this same problem awhile back and he posted on it. I emailed him and he said his problem was trapped air, and they drilled a little hole in the thermostat to fix the problem.

Any ideas?