Go to a mechanic and have the pressure test the system and do a block test. The pressure test will determine if there is a leak in the cooling system and where at and the block test will determine if you have a blown head gasket. Check your oil and see what it looks like. If it has coolant in it you may have a blown head gasket which isn't cheap to fix.
What year wk did alot of people have problems with the head cracking inbetween I think cylinder 3 and 4