C220 CDI: Rattling Noise on Startup

Hello,

I have a '99 C220 CDI. This morning, I tried to start it, but it wouldn't start. When I try to start it, I hear a rattling or clattering noise. Can anyone help me with this?

Hello,

If the rattling sound is coming from the KAT unit, it's possible that the monolith has become detached and is blocking the KAT.

It seems to be coming from the direction of the clutch, but the clutch pedal feels normal and can be pressed as usual.

Hi,

Perhaps the starter motor isn't engaging properly, or there might be a problem with the power transmission.

hello,
I also think the starter motor is likely the culprit. Your starter probably has a planetary gear system that can break and then produce noises like that. (Have you ever tried starting it by pushing? Does it work then without the strange noise?) Of course, it's difficult to diagnose a noise that you can't hear. That's why my suggestion is to record the noise and upload it as an MP3 file so we can listen to it.
Gerrit.

Hello machine,

I don't think the starter is the only likely culprit. Faults can also overlap or occur in quick succession as a result of each other. If you're sure that your machine (or engine, strange name - you're probably much more than that...) has the basic prerequisites for starting (e.g., battery voltage, control signals), you need to listen carefully to pinpoint the source of the noise. If the starter sounds normal, as far as you can tell from the noise, things will become more complicated. Your engine may not have a dual-mass flywheel, but perhaps a clutch spring is broken and rattling a bit... You need to better localize the noise!

Hello,

Thank you for your suggestions. The starter motor engages normally. The engine turns over normally. Regarding the OM 611 engine, if a clutch plate spring were broken, the engine would start, but it's not starting. The noise (a metallic clanging sound) seems to be coming from the clutch bell.

Hello machine,

Are you sure the preheating system is working properly?
Perhaps that unusual sound seems strange to you simply because you haven't heard it for so long before! A diesel engine makes a bit of noise, that's normal!

Since I'm completely unfamiliar with the C220, this is just a shot in the dark: Could the OT (output transistor) sensor on the clutch bell have disintegrated, with pieces falling inside (and now rattling around)?
Does the C220 even have a knock sensor?

It would be a good idea to have the error codes read now. Perhaps you could borrow a suitable device for that?

Best regards, Rainer.