presure in cooling system

[bushwacker]

hi all do not want to sound dumb, but is the cooling system presurised,as when i take the cap of the expansion tank it releases air ie it hisses wether its hot or cold ......pete

[bigdazz]

this is normal

[Krusher]

Yes its normal for the cooling system to be pressurised when hot especially, when the system is cold you may get a small hiss of air
escaping but not much...Hope this helps

[Rifleman]

Be careful though, as you are not meant to remove the cap when the system is hot, or you may get scolded as the hot coolant squirts out. Release it slowly to allow the system to depressurize slowly.

[Drift]

As Keith says, If you need to open it when hot get a large heavy rag draped over the top this will arrest most of the water squirting out.
I once saw a mate open a rad on an overheating bus in Liverpool City Centre years ago, the water came out about 15 foot into the air, he was bloody lucky it missed a load of pedestrians
He didnt get scalded as the old buses had flick caps, so he hit it and ran.

The Fronty should spray that far but if it gets you it burns