Strange engine noise
Thread Starter
Newbie
Joined: Dec 2014
Posts: 4
Likes: 0
CLK 200 Kompressor
Strange engine noise
Can somebody tell what is this strange rattling noise when pressing and lifting off the throttle? Is that the timing chain or chain tensioner? Or something else? 
Thank you in advance!
Thank you in advance!
Newbie
Joined: Dec 2010
Posts: 14
Likes: 0
1996 SL500
That's curious... I have a couple of thoughts:
I doubt that a timing-chain tension noise would ever be so oddly dependent on RPM or on-off throttle, as your noise seems to be... Typically, timing-chain related noises are pretty constant once they start.
Also, at the RPM where that noise shows up, the teeth of the chain are moving so incredibly fast that you wouldn't be able to hear independent strikes or rattles, again, as your noise seems to present...
My crazy guess is that there is simply a lose fitting of some peripheral component on the engine - it almost sounds like one of those tie-down metal latches used to secure the plastic engine cladding or air-filter housing, etc., which is vibrating and rattling when the engine gets to a certain band of harmonic intensity. I'll play the video for my MB mechanic (he's excellent) later in the week, and will report back on his thoughts...
Just FYI: I have an old 911, and I was 100% sure I had an intermittent timing chain issue, as the sound was exactly like what you'd imagine a chain to sound like while running over a tensioner and the engine was at idle... Nope, it was just a valve in the oil system that rattled at certain temperatures and conditions.
I doubt that a timing-chain tension noise would ever be so oddly dependent on RPM or on-off throttle, as your noise seems to be... Typically, timing-chain related noises are pretty constant once they start.
Also, at the RPM where that noise shows up, the teeth of the chain are moving so incredibly fast that you wouldn't be able to hear independent strikes or rattles, again, as your noise seems to present...
My crazy guess is that there is simply a lose fitting of some peripheral component on the engine - it almost sounds like one of those tie-down metal latches used to secure the plastic engine cladding or air-filter housing, etc., which is vibrating and rattling when the engine gets to a certain band of harmonic intensity. I'll play the video for my MB mechanic (he's excellent) later in the week, and will report back on his thoughts...
Just FYI: I have an old 911, and I was 100% sure I had an intermittent timing chain issue, as the sound was exactly like what you'd imagine a chain to sound like while running over a tensioner and the engine was at idle... Nope, it was just a valve in the oil system that rattled at certain temperatures and conditions.
Thread Starter
Newbie
Joined: Dec 2014
Posts: 4
Likes: 0
CLK 200 Kompressor
I found what is causing the problem. It is the variable valve timing adjuster on the inlet camshaft. I have disconnected the cam adjusting magnets electrical connector and the noise disappeared. If I connect the cable to the electromagnet the sound reappears immediately. The adjuster needs to be serviced or replaced...
