G'day guys,

Recently I've noticed that the coolant reservoir in my 2004 Gu3 is bubbling. I took it to a mechanic and they said it might be the head gasket when doing an overall checkup (no pressure test or anything). The car was fine when I bought it (340,000 k's). It doesn't overheat at all, I have noticed some loss of coolant and noise from the coolant when I accelerate.
I took it to another mechanic and they assured me they were sure it's not the Head Gasket because it's not showing any signs of it (oil, startup, steam from exhaust pipe) but rather the EGR. He booked me in to get it blocked and said it should solve the problem. Is he just giving me false hope or will this fix the problem?

Has anyone had a similar problem before? Or can make any suggestions? I'm not too mechanically minded but eager to learn.

Thanks