Magic coolant problem

[stu1806]

Hi,
I've got a strange problem that has been ongoing for about eight weeks now. The "STOP CHECK COOLANT" warning light and beep come on the dashboard but the actual temperature needle does not rise above the normal position. Most times when I open the bonnet the expansion tank is showing nearly empty.When i release the cap the coolant usually floods back into the expansion tank. This is the case nine times out of ten.Ocassionally however the tank remains almost empty and i have to add coolant. I have had the car running for hours (while parked) and am unable to see any leaks. I've had it parked on cardboard and still no evidence of leaks. Obviously there has to be a leak somewhere but i'm unable to find any evidence anywhere. I've tried to bleed air out of the system by topping up tank to brim and leave running till air comes out. Quite a bit of air came out but this hasn't solved my problems. Any help would be greatly appreciated.Thanks in advance.

[Quatrelle]

I seem to recall someone had this problem a while ago. Might be worth doing a search (but don't use the word 'magic'!).

[stu1806]

Thanks for the reply. I've tried to search using all sorts of combination of key words. Not found this problem yet but will keep looking.

[Quatrelle]

Did a search on 'coolant level' and found these - don't know if they're any help.

Coolant Level Cold

Coolant Loss

[stu1806]

Thanks. Had a read of the links you added and found similar ones myself. The few threads I've read seem to not have a definitive answer. I found one suggesting a possible leak on the radiator which might be helped with rad weld. Other than that it seems it's the head gasket although I've got none of the symptoms. I'll give the rad weld a go first and let you know how it goes. Thanks for your help.

[Peter D]

It appears your coolant system is being over pressurized by combustion gases. Get a garage to test the header tank fumes before you do anything. Regards Peter