coolant steam!

[lowrider]

After a sporty drive home tonight I parked up to find steam coming form the coolant overflow tank.Whilst this was happening the temperature sensor remained unchanged(in the middle) It settled after I switched off the engine and even though it steamed heavily the coolant level has not altered much.

Help:frown:

[Colin]

Could you see exactly where it was coming from, the cap or one of the seams. Maybe you have a small split that opens up when the pressure gets too much.
Certainly should not be doing that, it's a sealed system. That's what the expansion tank is for to let the water expand when it gets hot.

[lowrider]

Looked like it was coming from the cap. Which I presume has a pressure release,but then surely it would show as overheating on the sensor?

[lowrider]

Update....

There no longer appears to be steam coming out and the coolant is no longer bubbling as much. I read a few threads about head gasket failure and am worried.I have checked the oil for white deposits,nothing.

As there seems to be an issue, I am checking the coolant on every journey,don't want a cooked engine! When I park up the level seems to rise from between the min/max to around the inside lip (where there is a join towards the top of the tank) If I start the engine immediately the coolant returns to its original level,that is, between the min/max. Is this ok?