i first thought it was a bad thermostat. lower hose wouldnt get hot, and radiator cap was never hot either. i replaced it, same results. to be honest, i just bought the car recently. ran fine on test drive, temp guage read normal, below half, after driving for a couple days, i smelled antifreeze when i parked it. popped the hood and saw it shooting out of the little hole in the top front of the resevoir.
after reading several posts on here about the phase I 2.5l, it has all the signs of the HG being bad.. car is very clean, no rust, 131k on it. but i dont have any idea if/how bad it was ever overheated by P/O. i bought it as a winter car, because i dont want to drive my super clean xt6 thru the salt, and my avalanche has a big block in it, so gas mileage in that kills me. i think i made a huge mistake thou!!