Water out of over flow

[Jtrigga]

So I changed cambelt and water pump on the gti about a month ago and since then after a longish drive or a hard drive il turn the engine off and water will come out the over flow pipe. I've bled it all up the temperature sits nice the water isn't pressurised and the heating works nice so I'm quite confused what it could be.

[Tom]

Buggered rad cap?

[Piggy]

If its not pressurizing (more than it should...it does need pressure to maintain its temps) then it has to be rad cap either gone or not screwed on right. or lost its seal perhaps

[Jtrigga]

Oh yeah I forgot about that il have to try another one is there anyway to test the cap?

[Tom]

It should have a spring in it, id guess yours doesnt, or its very very weak. Mines hard as f*ck giggidy.

[Jtrigga]

Yeah mine has a spring you can push it down if you squash it with 2 hands.

[Niall]

Yep buggered rad cap or the neck on the bottle on the rad. The neck on mine is shagged and does the exact same. Never bothered me.

[Jtrigga]

Yep buggered rad cap or the neck on the bottle on the rad. The neck on mine is shagged and does the exact same. Never bothered me.

Yeah it only does it when I stop and turn off the engine do you have to keep topping yours up then?

[Jtrigga]

Wound this cap be alright to use it says 20psi which I believe is the right pressure

http://bit.ly/1dqtFKT

[Niall]

Yep buggered rad cap or the neck on the bottle on the rad. The neck on mine is shagged and does the exact same. Never bothered me.

Yeah it only does it when I stop and turn off the engine do you have to keep topping yours up then?

Nah eventually it will blow enough out so that theres enough room in the tank to expand and not blow it out and its only just below the max line.
Also, new genuine rad cap from Pug is only about 7 quid

[Jtrigga]

Yep buggered rad cap or the neck on the bottle on the rad. The neck on mine is shagged and does the exact same. Never bothered me.

Yeah it only does it when I stop and turn off the engine do you have to keep topping yours up then?

Nah eventually it will blow enough out so that theres enough room in the tank to expand and not blow it out and its only just below the max line.
Also, new genuine rad cap from Pug is only about 7 quid

I get it now that's why when I top it up it blows out the top again and doesnt do it all the time thanks for your help everyone.

[x-axis]

Definitely the rad cap. I had the exact same issue last week. It stopped immediately after I changed the rd cp.

[bitwrx]

Important to have a rad cap that maintains pressure because it raises the boiling temperature of the coolant. Not a worry at the rad, which will not get above 90 deg or so, but when you switch the engine off, stagnant coolant at the hottest bits of the engine will boil, expand and push coolant out.

When running, any steam produced at the engine will reduce the heat transfer and you will get hot spots. Hot bits of engine are bad.