Manifold leak or induction noise when cold

[macca2210]

I've got a '94 E220 (W124) with about 200,000 Klms

When the engine is cold, it sounds like it has a leak in the manifold, but I cant seem to find the leak. From outside the car, when it's accelerating away from the house, it sounds like a hole in the manifold close to the head (quite a sharp sound, and sounds like one cylinder).

With the bonnet open, it sounds like the noise is coming from the induction area. It's not there at idle, but with a few revs the noise is quite loud. Seems to run OK when the engine is hot.

So now I'm puzzled at what could be the problem. Any suggestions?

Many thanks

 

[Bolide]

Has your car got an air injection pump? It's on the left hand side of the engine compartment above the alternator. These things rattle away for about a minute after starting. Some UK cars have them

Nick Froome
www.w124.co.uk

 

[macca2210]

Has your car got an air injection pump? It's on the left hand side of the engine compartment above the alternator. These things rattle away for about a minute after starting. Some UK cars have them

Nick Froome
www.w124.co.uk

I don't think so Nick. The engine is a 4-cyl twincam model M111.960 . In the workshop manual I have, it shows an air breather from the crankcase to the head, but no pump. (There is a reference to a pump for the older generation 6-cyl engines only)

 

[jibcl500]

Are you running LPG?

jib

 

[macca2210]

Are you running LPG?

jib

No. Just running normal premium petrol 95RON.

I'm wondering what happens if the VVT plays up - could the valve timing be wrong if the mechanism wears etc...