Rattling noise when cold

[Zrun]

I've this rattling noise from under the car(or from engine) when engine is cold..

 

Strange thing is that it only occurs at about 1400rpm-1600rpm..

 

When the car starts at cold, the sound is quite obvious, as the car idles at 1500 rpm... If I step on gas slightly, it disappears at 2000rpm.

 

The mechanic says it is the lifters.. But there's no sound before he changed my clutch and flywheel. I think it is the exhausts pipes somewhere...

 

Just got my clutch, seals, flywheel, starter changed... The clutch feel deteriorate after 1 week or so.. I think some oil is leaking on the flywheel.. Obviously, the mechanic is not going to dismantle my transmission for free just to check for any leaks again..

 

If clutch is oil contaminated, what possible cause? Engine oil leak? Transmission oil leak?

[Turbobrick]

The cat-convertor could have worn out, the ceramic inside may have broken apart and rattling inside.