M-a-x-G

Funny noise when starting the car: a S350, W211, 6cyl.
Every now and then I have the funny noise after starting the car; it settles within seconds, and only occurs occasionally.
I was able to record it. Any technicians or others might have an idea what this is?
Apart from this, the car runs fine.

Any hints appreciated.

M-a-x-G

Looks like it is the timing chain tensioner...

becosemsaida

Timing chain tensioner, oil spec not recommended by MB, oil needs to be changed??. Faulty oil pump (hope not). Seems like the oil takes time to com up to the heads, or it might just be the chain tensioner that's worn, little peace of plastic but the labor to fix this...........

I recommend NOT to use the car much until you have sort this out.

Beco

M-a-x-G

Oil as per specs... service due in 3,000mi (5,000km). I am ruling out the oil pump, as the sound goes away after a few seconds. Pressure is there, otherwise I expect a light or warning to come on. Most likely not the guide rails, as the car has only 60,000 mi (95,000km) on the clock.

Two weeks ago I got a P034600 The position sensor for the intake camshaft (bank 2) has a malfunction, which is either a separate thing or due to the dying tensioner,

I'll book the car in for a service soon... will be interesting as to what they have to say. (Will report beck here.)

M-a-x-G

OK... further update.

The oil is according to spec; was for a B-Services at the Merc dealership.

I replaced the cam chain tensioners and installed the check valves on both banks. No improvement.
(BTW: the tensioners were already the modified ones, implemented in Jan 2011 when the car/engine was manufactured.)
Something still rattles for two seconds on cold (engine) start. Given the short time it takes to fix itself, I still assume it has something to do with oil pressure being built up, but I could be wrong with my suspicion.

Any experiences with this sound / problem?

I have one trouble code left: P002177 The position of the intake camshaft (cylinder bank 2) deviates from the specified value. The commanded position cannot be reached.

I have also replaced both (intake/exhaust) camshaft position sensors on bank 2

What else should I be looking at. Any hints / help appreciated.

Marc Jackson

M-a-x-G

Cold start rattling can have multiple reasons.
Given the cost associated with troubleshooting and fixing this issue, I started with systematically addressing this issue.

The easiest fix (for me) was to replace the camshaft chain tensioners. As it turned out, despite the information about engine numbers, which have or do not have a potential tensioner issue, my engine built in January 2011 already had the modified tensioners installed... which is something I realised when I replaced them.
I also installed the check valves. In my opinion (because I did not take rattle duration timings with a stopwatch) I think the rattling is a second if it all longer (can't really tell). The only evidence pointing in that direction is that I now get an engine light coming on once a week which is directly related to this issue... and which may clear itself after some time.
When I changed the tensioners, I also changed both camshaft sensors on bank 2, while I had the intake manifold removed to change the spark plugs. I did this because of the DTC: "The position of the intake camshaft (bank 2) has a malfunction." (Just in case; and the sensors were significantly cheaper than visiting the stealership).

Given all these changes without improving the rattling, I now concede that the chain must have lengthened... and decided to keep driving the car as it is, I am doing 1,000km a week (625 miles), there has been no other concern or issue than the cold start rattle.

The options I have left:
1. replace the third chain tensioner (a relative pain to do)
2. replace the chain only, which can be done without pulling the engine, but leaves the old guide rails in place (all of which seem in a condition to do another 100,000km).
3. pull the engine and replace chain and guide rails. (right, lots of work; leading to the question, why not replace the engine given the effort.)
4. get a refurbished replacement engine (quite expensive, and because it is refurbed, things with borderline tolerances could cause early problems).
5. get a new replacement engine (I reckon this will cost even more, but should mean a long life).
6. sell the car as is (given that I am done with ICE cars; my next car will be an EV, clearly eliminating engine and gearbox trouble).

This M276 engine has three chains. The bottom one is unheard off to cause problems. The middle one was replaced from what I understand based on my research, but not the tensioner. Given the short length of the second chain "I do not believe" (always a funny thing to say without evidence) is the culprit, as I think it is too short to make this kind of noise.

Once I have some spare time, I mostly likely opt for replacing the chain only; mainly because it is the least costly effort. Take off air intake plenum and bank 1 camshaft cover, cut a chain link, connect the new chain, manually turn the crank until the new chain comes back, put a link in, and we're done. I would also remove the check valves I've installed.

All these decisions and suspicions are based on my understanding of this engine based on research and gained from forum posts.
I am certainly inviting further hints and ideas from actual mechanics / engine rebuilders.

Marc Jackson

M-a-x-G

I hope this will fix the rattle issue for you; given the time since your post: did it fix the problem?

Marc Jackson

rustybear3

That's one expensive rattle.

teksurv

I had a similar rattle at start on my 2013 C350 (M276) and two chain tensioners were replaced. I don't know which, but this is common within a certain range of M276 manufacture.

M-a-x-G

Thanks; when you say 'camshaft', what exactly was it? Maybe you have a part number on the invoice? I'd really appreciate your response. Thank you.

M-a-x-G

Further updates; however, none the wiser.
Had the car at the dealership. Used a stethoscope to figure out the rattle.
Identified two sources: 1. coolant pump bearing; validated by throwing the belt off; noise gone.
2. Camshaft clearance in valve cover, or camshaft adjuster.

The more I think about this, it seems like the adjuster.
It is not the oil pressure; that has been check and found OK before the oil was changed.
Tensioner replacement and check valve install did not improve the situation.

Given that the camshaft position sensor reports incorrect or implausible position, thus triggering the 'check engine' light, it seems save to assume the camshaft adjuster is defective.

Any further thoughts or input based on my description?

M-a-x-G

Eventually made it to the workshop in September.
The left intake camshaft adjuster was the problem, has been replaced and the rattle is gone.

artim808

Did they replaced chain as well or only the camshaft adjuster?

M-a-x-G

Camshaft adjuster only.
Unless there is a lengthened chain, there is no need to change the chain.
The four adjusters have individual part numbers, meaning they are all different.
Some change one bank, others both banks. I decided to only have the intake left fixed, because the intake left seems to be the one most commonly failing.
.

DennisW212

Hi I have the noise upon start up with the same code P002177 is this the driver side intake cam adjuster bank 2? on LHD vehicles I was thinking of just replacing one adjuster they are expensive

M-a-x-G

Based on my research, it is almost always the left (in driving direction) camshaft adjuster.
I took the risk and had one fixed; that approach worked for me.
On that note: It was replaced at 143,373 km; I now have 165,738 km on the clock. So, 22,365 km later and she still goes like clockwork.
Good luck with it.

mercyfan

Is left in driving direction that mean on driver side in US?

M-a-x-G

Left is left, no matter where you drive; maybe I should have clearer by saying left side of the car.