Hi folks. 84 242 Turbo. The car has started to make a horrible sound from the exhaust side of the engine compartment. I am pretty sure it is an exhaust leak, but am afraid that it is a rod knock. Here are the symptoms:

1. loud popping / banging sound at idle. smooths out as rpm increases, but is stillpresent

2. 99% sure that the sound is coming from the exhaust / turbo side of the engine (possible audio illusion?)

3. car has always had a little exhaust leak where the cat flange attaches to the turbo. that is still present and I can hear it beneth the new sound. I did re-tighten the nuts there in hopes it would fix the problem. It didn't.

4. some fumes / smoke in the engine compartment (I think these are new)

5. I can place my hand between the exhaust side of the turbo and the exhaust manifold and feel a warm air breeze. This has been present since before the new sound. I have not been able to determine the exact source of the air leak

6. The downpipe from the turbo to the cat is intact with no holes.

The way I figure it the possibilities of this are:

a. bad exhaust like at cat flange / turbo outlet

b. leak where turbo meets manifold

c. leak where manifold meets head

d. cracked manifold

e. rod knock making believe it is an exhaust leak

I am sure there are some other dooms day possibilities (cracked turbo housing). Any ideas on how I should go about trying to track down the source of the leak?

Thanks,

Dave