W203 270cdi auto noise

[mornin clatter]

Any ideas would be greatly appreciated , i posted a youtube video with the noise, it was filmed while the car was in P. I noticed that the sound will occur no matter what the position of the gearbox lever, no matter if the car is rolling or is parked. As a rule it will start only after the engine is hot and between 800-1000 rpm, i can never get her to make that sound when first starting on a cold engine. I managed to get under the car yesterday, and pushed and moved the exhaust while the sound was made , without any results. So i suppose it has nothing to do with exhaust supports, and it seems to come from the upper part of exhaust, my guess being the cat converter. Nothing out of the ordinary, no strange turbo noise, no smoke , pulls well.
Thank you for taking the time to read.
https://www.youtube.com/watch?v=7i4hfK96Rgc

 

[whitenemesis]

I'd suggest the parking brake cable clips rattling, or the cable contacting the propshaft.

Try tapping the cat, possibly loose innards?

 

[mornin clatter]

Thanks for the quick reply, i will have another look, and try to locate the clips.

 

[panason1c]

It could be one of the pulleys or alternator belt tensioner..... remove the belt and run the engine with the belt off to see if the noise is still there.

 

[mornin clatter]

HI panason1c, i checked the belt and pulleys and they are ok, that was my first idea as well.

 

[BlackC55]

Worn engine mounts?

 

[mornin clatter]

The best way to check engine mounts?
Just grab the engine and try to move it or is there any other way?

 

[Leabrooks]

Check the centre exhaust connection (after the rear cat) roughly under the middle front seat area where there's a flared joint with a large clamp around it. The clamp can sometimes break causing leaks, and the flared flanges on the pipe can rot though at this point (hidden until the clamp is removed). My 270 had this problem, the clamp had broke (a tenner from MB) and the flanges had pin holes in them yet everything else was sound, a new clamp, some epoxy metal weld stuff (to repair the holes) and new exhaust jointing paste cured it. Paint the lot before fitting the clamp with some aluminium paint.

 

[Leabrooks]

I should add its not a simple slot over exhaust joint (as most exhausts), its a ball and cup arrangement with the bracket pulling the two pipe ends tight together.

 

[mornin clatter]

Thanks for the reply. As i was under the car and got someone to hold the revs to reproduce the sound i could definetly hear it coming from the area that you just pointed out. I just have to remove the clamp next time and have a better look at the exhaust connection. Did your car made a similar noise? Thank you.

 

[Leabrooks]

Yes, mine sounded just like that. Be warned on removing the rear silencer (to effectively clean the joint of old exhaust paste) that you might find your rear silencer has rust holes in it and may need replacing (as mine did). I replaced the rear silencer with an Eberspacher replacement (excellent quality) repaired the pinholes in the 'ball' on the rear of the cat pipework, smeared exhaust compound on the mating faces, aligned the new rear box assembly in its rubber hangers and fitted a new clamp (from MB dealers) and then painted all pipework with alu paint for extra protection. If your lucky your rear box will be OK and will just need removing and refitting, they are pretty easy to remove (but heavy, so put a jack under the rear box when removing/refitting, or get a friend to help). HTH

 

[mornin clatter]

If you don't mind , why is it necessary to replace the clamp, does it become loose ?
So the cause is the pinholes on the mating surface or the clamp.
Thank you.

 

[mornin clatter]

Problem solved , it was just as Leabrooks said, the noise came from the exhaust joint, but i got off easier, as i only needed to apply exhaust paste, and no more noises.
Thank yoh Leabrooks!