Air in coolant

[ozzy]

I keep getting air into the cooling system and have to bleed the said system every 2 months or so.
Im not losing any coolant and its clear with no oil or fuel in it just every so often i can hear the air glugging around and it displaces the coolant to the top up resevoir wich gets full upto the filler cap.
If it is the head thats cracked is there any stuff that can be put in to seal it.
I know this is a temporay measure but i intend to drop a new Vege in when the old one finaly goes to engine heaven.
Apart from this the engine runs brill so could it be something else? Is there a test that can be done to find out where the air is coming from?
anyone else got/had the same problem.

[banana]

Spent the summer with this problem on my T25 1.6TD diesel ( notorious) but it was 127K. The water levels would drop and eventually an air lock from pressurisation would go to the radiator and then overheating occured because the fan would not cut in because of air around the sensor.. Once I stopped moving the water temp shot up. The garage pressure tested the van and found no leaks and it retained pressure. But water loss was 1 litre every 100 miles. Changed cap etc but no solution. Had to be a head gasket and not really worth changing. Bought a recon engine. less smoke, less oil consumption, no water loss yet.

[ozzy]

Im not losing any coolant just gaining air???

[TD]

If you ar egaining air, where from?. It is either leaks at joints/cracks in expansion tank or rad/pipes/
But to gain air you must dispel coolant to the top up tank.
sounds like pressure from cracks?

[hanloncole]

Not being funny, have you bled it properly there is a procedure to do it lifting the front of the van and ensuring 2000 revs whilst you fill up and also whilst you open the tap at the radiator keep the revs to at least 2000. Do you have a heater in the rear these also need to be bled too, and often leak unoticed. I had all this with my TD too following a coolant change would overheat and spew out coolant, only when i followed the bleeding procedure fully did i get agood result
Simon