Where is the anti-freeze going?

[Stirling]

I just came back in from topping up the anti-freeze in the tank. I can now drive 5 km or 500 km and at the end of the journey the tank will again be about 1" below the cold fill line.

I haven't seen any leaks anywhere. Is this the result of an air pocket?

[Scooter]

I'd start by replacing the rad cap.

[quattro20v]

I had a small leak at the after run water pump. It was hard to find as the water would vapourize immediately as its so hot. Its located on the passenger side firewall. I replaced this along with the hoses and that solved my problem.

Worst case, you may have a head gasket leak. Check to see if you have any oil residue or film in the expansion tank.

[quattro20v]

Its located on the passenger side firewall.

I meant to say, the coolant pump is on the passenger side, mounted on the inner fender.