Hello all,

I'm hoping the collective wisdom here can help please

My c200 with 240,000 kms on it has started making some strange engine rattles at hot startup (occasionally, and only for a second or 2) and today it started rattling (differently) at idle/low revs, particularly whilst on a slight uphill incline. At normal revs driving and whilst on the flat she seems to be running OK. I've checked the oil and everything appears fine and there's no code/dash alerts.

Any ideas as to what might be causing this?

Edit: it appears that the two issues might be unrelated, the first could be the cam chain tensioner, but the second item, I'm not too sure.

Edit 2: I've taken her for another drive and the 2nd engine rattle is persisting at all revs, but more pronounced at idle/low revs. A quick look under the bonnet shows minor oil leaks as per the photo - is this a clue to the problem?
This is my daily driver so I'm keen to get this fixed asap

 

What sort of oil change schedule do you follow??

What oil grade do you use ??

Do you know that engine oil thins out increasingly as it ages and as it enters operating temperature.

 

Oil is changed whenever the service alert pops up, IIRC its about every 15,000kms
Synthetic 5w-40

It was a warmer day than usual today (early spring here), and this did start happening after a longish drive, so I suspect that has aggravated things

 

15,000km is waaay too long for timing chain engines, I recommend to my clients to change the oil/filter every 5000 - 10,000 km max. Regular & often oil/filter changes are the secret to the life of timing chains.

I think the wear is already done to the timing chains, but you could try changing the oil & filter & see if it improves the issue.
Also you have to realise that the engine has done 240,000 km, (with extended oil change intervals) so you've done well to get this far without any issues.

I think you will find the two oil leaks you have highlighted are irrelevant to the issues at hand.

 

Thanks for your reply and please don't quote me on the 15k service intervals, I simply change the oil when the car alert tells me to, whatever frequency that might be.

I think that whilst the cam chain tensioners are due for replacement and part of the first problem, the second (more pressing) issue/rattle is possibly oil pressure related (?) as it happened after a longer-than-usual drive in warmer weather. I've just restarted her from cold and the issue has disappeared. I'll take her for a run tomorrow and see if the problem reoccurs, and change the oil this weekend either way.

Yes, 240ks is a good innings, but the car upgrade isn't planned for another few months so i just want to keep her in good usable order till Dec/Jan - She has been fantastically reliable for the last 10 years of ownership and hence a new one is in the pipeline.

 

As an additional note, when I checked the oil level when the engine was hot, and rattling, the oil level seemed higher than usual - could this be a sign of something?

 

10kMi oil change
While following recommended interval is possible... 10KMi is twice as long as it really should.

Once the engine oil is burned black it looses its hability to remove heat effectively.

The low oil pressure is what causes the VVT gear to wear out its lock pin to rattle loose. Don't ignore rattling too long or the camshaft will also need replacement. Chain tensioner has been limp since the very early stage.

This is producing metal particles in your engine that can be dangerous for spun bearings.

Your best interest is to be pro-active to minimize cost.