Hi.
I got another problem with my 4x4 Saph.
I've just rebuilt the engine.
During driving with normal speed everything seems to be right. The temp. gauge shows "O" (maybe a little to high, but sometimes between O and R), temperature outside is about 27 - 28°C.
When I get back home and turn off the engine, the coolant in header tank starts to "boil" after about 1 minute. (I see bubbles coming out from the turbo return hose).
As you see, the coolant level raises just to the cap. All the "boiling" takes about 2-3 minutes and when it cools down, the water level returns to the normal (max mark).
Radiator fans are working okay. I cooked a thermostat in a pot and it's good (opens just before the water starts to boil). I replaced the tank cap. I made two "CO₂" tests on hot engine (one of them for over 4 minutes). The reactive fluid does not change the color, so I think maybe there are no exhaust gases in the coolant. There's no coolant in oil and no oil in coolant. I did not touch the "bleed screw" on the thermostat housing.
Can you tell me what may be the reason for such water boiling? (I got another cossie and it doesn't boil the water so intense after turning off the engine).
What else should I check?
Thank you for your help!