I'm afraid they were my symptoms too, I replaced the radiator as I thought this was at fault but still my coolant would disappear. The sniff test confirmed the hydrocarbons in the system, although it didn't change colours immediately so I'm hoping its a minor gasket failure.
I had to drive 80 miles home today so a hot day combined with the knowledge that the head gasket had gone made me extra paranoid. I drove with my heaters full on sweating my **** off, the temperature gauge didn't go much above 90 but I pulled over three times to check the coolant levels, there was some weird stuff happening that my baffles my A-level physics.
So water temp gauge at 90 degrees, under pressure due to pressure cap, coolant mixed with water....in my mind this should raise the boiling point of water, yet my coolant was bubbling up and escaping at 90 degrees.
The fan was kicking in ok, worryingly when driving its almost impossible to know when the coolant is escaping.
One of my theories is that when you fill the coolant up its cold water in between minimum and maximum, as the temperature increases the volume of the water expands (not sure whether this is the case...) during this time the water leaks from the expansion tank whilst driving. Then when parked up, engine off, the coolant cools and the volume decreases.....dropping to a level at the bottom of the expansion tank.....its almost as though the expansion tank is the wrong size. I figure that maybe my pressure cap is faulty too but guess it could be exhaust gases escaping into the coolant....
Can anyone explain whats happening.....videos here .....
YouTube - ‪VIDEO0041‬‏
YouTube - ‪VIDEO0042.3gp‬‏