KSira

So my car is loosing water. When the overflow tank is filled to maximum mark when cold, and the car is driven for a while with boost, and then stopped and idling, it looses a lot of water trough the overflow hose. It also looses water while driving.

Also the temperature tends to get high after idling a bit, but drops instantly when revving the car. Currently I'm thinking air or broken water pump. The system was drained this winter, and the idle temp was better after bleeding the system.

Any thoughts? Try bleeding again or is time to pull the head?

Mighty Shilling

start with a new reservoir cap.

KSira

The cooling system holds pressure even after a couple of hours and when opening the bleeding valve the pressure seems to be very good.

fortysixandtwo

Still, try a new cap first, they're cheap.
If its the head gasket, I suppose the symptoms will be somewhat dependent on how bad the leak is. I recently pulled the head off my car and found, as I suspected, that the head gasket had failed. My symptoms were; an erratic cold idle, loosing coolant when using boost and dirty coolant from combustion gasses. If driven without using boost, there would be no coolant loss.