I've recently had the intake manifold gasket (and intake manifold as it was corroded) replaced by a local mechanic. The parts including the manifold were all OEM.

Since the repair, I've had to top up the radiator several times within probably about 400 miles of driving. Usually what would happen is that the "low coolant" light comes on and when I check the level in the radiator once the engine has cooled down, the level in the radiator is between a 1/4" to 1" below the filler/pressure cap neck on the radiator. I followed the instructions in the owners manual - start the engine with the cap open, top up until the coolant level reaches the bottom of the filler neck, then put the cap back on. Header tank is filled to the "hot" mark at this point. Driving the car at this point shows normal engine temperatures (185-200 degrees, I rarely see the temperature hit even 210 in the mountains). After letting the engine cool down over night, I noticed that the level in the header tank only changed minimally, if at all. this behaviour was present before the repair, too - the level in the header tank pretty much never changed.

Last night when I checked the level in the header tank with the engine hot, I noticed that there was a sound of gargling/boiling coolant from the front of the engine, somewhere below the throttle body. Given the engine temperature (coolant was around 200F when I turned off the engine), I was a little surprised by this, is that normal for a C4? The only other car/truck we've owned with a similar engine (a slightly newer GMC truck) certainly didn't do that, but that one also ran at an indicated 210F once the engine was warmed up.

Apart from the new manifold and gaskets, the thermostat and the radiator cap were both replaced with OEM-spec parts (ie, no low temperature thermostats or high pressure caps).

I guess the main question is - is this normal behaviour, or do I need to take the car back into the shop? I normally do most of the work on our cars myself and at this moment I'm kicking myself that I didn't do this job myself, too.