[ripley]

Hi all just changed the head gasket on a 57 plate corsa d all good started first time job done....went for a run and all looks good untill i popped the bonnet and found the water was boiling out from the header tank....not so sure what to do now i hope its just an air lock and it will sort its self out or could it be that the head is warped???? any input would be great thanks terry.

 

[GRAHAM.C]

Did the engine overheat before you changed the head gasket ? If it did it would have been a good idea to have had it checked and skimmed,if not it could possibly be warped which would make it blow again.
If that is not the case,it is most likely air locked.You need to fill them at no more than a trickle.You could try filling it,run it with the cap off with the heater on full,and while running keep squeezing the water hoses.

 

[Walksall]

It may well be, as said above that you were in too much of a hurry to put the coolant in!

If it overheated before the gasket was changed, the head COULD be warped, but I would be inclined to find WHY it overheated in the first place - likely causes of overheating:
1) Thermostat failed (if you buy a new one, I would recommend a genuine GM one)
2) Blocked airways through the radiator (inspect)
3) Blocked 'water' passages through the radiator (is the coolant circulating?)
4) Failed 'water' pump -unlikely, but possible.

1,2 and 3 are worth checking before removing the head again.

Regards