AO Platinum Member
Join Date: Feb 2002
Location: The land that Time forgot
The header tank cap might be knacked. It's supposed to release pressure in the system at 1.2 bar or thereabouts. Stick a new one on there.
Another.. worst case.. scenario is that your head gasket has been mortally wounded.
If you have a bleed valve on the radiator (on the reverse of the top left or sometimes right as you look at it), try bleeding it when the system has cooled down. You should have no air in there at all. Do it again a couple of days later and see if the air has returned. Keep doing it until the air has all gone... or until you can say for certain it's always filling up with air from somewhere.. That's your HG.. blowing gas into the coolant.
You won't necessarily detect CO with a sniffer test and you may well have no water/oil mixing.. but if the system is pressuring up then start saving.
The only good news is that in this case, you usually get coolant blown out of the header tank cap (so you can see it all over the bonnet liner) .. If you don't have any coolant out of the header tank cap, then it could be that the header tank cap is just faulty.. which is where we came in...
No bullets for Chaingun..