Thread: Coolant Issue ~ TD5?

I have recently replaced the leaking plastic overflow hose with a one piece rubber one.
What I am now noticing is that when I do a morning cold check, the coolant level in the overflow bottle is down a few inches, however when I release the pressure cap the coolant flows back in to the bottle, almost to the correct level!

Is this possibly caused by an air lock in the system, assuming that the pressure in the system compresses the air, which would 'uncompress' when the pressure cap was released, (the air may have been introduced to the system when the overflow hose was leaking) or is it something more sinister?

Originally Posted by Redback

Mine used to do this, it did for quite a while, it stopped when I had my head gasket done.

Is it related, I don't know, might be wise to have it checked.

Baz.

I must admit that is one of my worries, but I can't understand where it goes to be able to return. The only thing that I could think of, was air compressing, as water/coolant can't compress.