Is my head gasket blown?

[Scottyboy94]

Hi, I have a 06 plate vauxhall zafira 1.6 club. It's done 98k miles.
I haven't had it long but the coolant is like grey sludge (which I know is a blown head gasket as oil is getting into the water). But before I bought it, the car had been sitting for a good 6 months. So I cleaned the coolant tank and put fresh water in just to see. Now no oil has gone into the coolant tank since but oil is going down quick.
The exhaust doesnt smoke and theres no warning of over heating but you you can smell burning when its heated up. There is a rattling noise when you put your foot down on the accelerator and lift off. Just wondering if it could be something else before I replace the head gasket.

 

[Burnerman]

I wouldn’t jump in with a head gasket replacement just yet.....rather, Id take the top off the expansion bottle, then rev the engine and look for air bubbles.
Check the engine for oil leaks......the head gasket can weep oil without pressurising the coolant.
John