oracle8dw

I have some concerns over the engine noise on the cold start. I've got my GL350 2011 54K recently. When I'm starting my car after it's been sitting for a while(hours), it makes loud flopping noise for a first 10sec or less, after that engine gets quieter when warms up. First I thought some parts (belt or fan) are loose somewhere (sorry for my ignorance).
Last time when I was visiting an independent mechanic for a "check engine" light fix (nox and cam sensors replaced), I complained about noise and was told that engine is fine and this noise is normal for a diesel engines.
It is my first diesel GL, but I drove BMW X5 Diesel for a month and it was noisier overall but did not have that startup flopping noise.
Any word of advise folks? What is your experience?

sak335

I have a 2012 350 that doesn't do anything like you have described. Mine starts right up and settles into an idle right away with what I would call typical diesel clatter, but it's quiet enough that most folks don't know it's diesel when they are riding in it.

jasonjeross

Timing chain! Check out my thread about this.

kooby

I have a 2011 GL350 Bluetec with approx 80K miles. I have the same issue, I have started hearing the clatter/knocking at start up over the past month. It happens always in the morning when the car has been sitting over night or after a few hours of sitting. This is not typical Diesel engine clatter but a loud knocking for 2-5 seconds just after start. The knocking goes away after (perhaps) the oil pressure builds.

The posts that i have been able to find to date deal with a member who was told that this might be a potentially stretched timing chain, but no resolution was ever found as the member traded the car in. (I'm not sure I'm ready to accept a stretched timing chain).

I have also see a member with a ML350 Blutec post in the pertol sedan thread as exhibiting the same symptoms, but no resolution.

All other posts that i could find on this topic deal with pertol engines, not related to diesels, although the noise is the same and the fix is a change of the timing chain tensioners and installation of check valves for the tensioners as these tensioners bleed oil out over a few hours. But again on petrol engines and not diesels.

If anyone could point me in the right direction, I would appreciate it.

KrustyKustom

I have a 2011 GL350 as well making the same flopping or chatter for about 4 seconds on a cold start....sometimes. I have had to the dealer twice, once for a week so they had multiple cold mornings and they determined it was in fact the timing chain but because it went away quick there was nothing they would be authorized to do.

I started studing the chain and tensioner myself. The tensioner is accessed from outside the engine block so I decided to replace the tensioner. Fairly easy job. When I got the original tensioner out you could tell the end of it had been "hammering" whatever it rides on and there was not a lot of spring tension on it. Now I understand it pumps up with oil pressure but with a new tensioner hand in hand there was significantly less tension. I installed the new tensioner, started it and the rattle was worse, then it went away for two or three minutes and slowly you could hear the sound coming back. Not liking that sound I put the original tensioner back in. All better, but I still have my cold start up flop.

Took it back to dealer and they say it may be a bad oil pump? I am just bummed as I have changed the oil every 5k and never cold start hard drive the car. I also have a 2012 Sprinter van with the same engine and it sound smoother than my GL through the rpm range making wonder if the GL is suffering from general low oil pressure causing some extra clatter? The GL has 55k on it and uses no oil at all, been a great vehicle aside from this but I am not sure what to do next?

kooby

This is exactly the same issue as I have. I was going to swap out the tensioner myself as well but now that you mention it did not help I'll hold off. I wonder if the tensioner requires check valves as in the petrol motors? Also, did you use an original MB part for the tensioner replacement or was it an aftermarket part? - not sure whether that would have made a difference. Please keep us posted!

It would good to here from others that may be having the same issue.

KrustyKustom

I used a original part tensioner. When I had it out I looked down in the bore and there is only a small oil port so if there is a check valve it is not like a gasoline engine. Also I pushed on the timing chain slider with the handle of a ratchet and it only moves about a 1/4 to 1/2".

Not sure what the next move is. I am sure over a lot of miles the loose timing chain is not good at start up.

Almost wish it had a manually adjustable tensioner so you just tighten it to where it was quiet.

kooby

Krusty - see the linked thread below:
https://mbworld.org/forums/new-m-cla...ml#post6048177

KrustyKustom

Thanks for the link. I am just out of warranty so the repair is on me. Hopefully we will hear back from the poster on the replaced timing chain service bulletin.

kooby

Yeah, I'm out of warranty as well. I've replaced timing belts before but never a chain. When you did the tensioner, did you notice whether you had good access to replace the chain?

KrustyKustom

From the timing chain tensioner access ( i removed the front wheel well liner) you could see what would have to come off. There is a housing that essentially bolts to the front of the engine the chain would ride inside of. Looks like a fair amount of stuff would need to come off including the main crank pulley. I may study up in startek info on the steps and also see how many hours they show to do the job.

I have gone from mad to concerned to wanting to trade it off, but then I get 29mpg on a weekend ride and can't see going back to a Suburban. I hope that guy posts what the TSB was for the repair as well as what parts were replaced.

samiran

Krusty (or anyone else) any progress diagnosing the cause of this problem?

I have a GL350 with the same issue. Was talking to an indy about replacing the tensioner, but this (and a couple other forums) seems to suggest that replacing the tensioner will not address the problem (particular a Jeep CRD forum).

Seems to be at least a handful of people have this problem, but no one has successfully fixed it.

kooby

It would be really nice if MB finds an easier solution to this like a check valve in the tensioned oil channel (such as the gasser solution) rather than a full chain replacement. I talked to an indie who ID'd the problem right away. He quoted me $1,500 parts & labour for replacement of chain and tensioner. Parts alone up here are about $500-$600. MB quoted $2,000 for the job.

Krusty - any more developments on your side?

KrustyKustom

No new developments from my side. I am just driving it, grimacing every time I start it cold. Mine sometimes does it and other times it does not cold. I just drove it 2500 miles on a vacation and got 15.7 mpg towing a 30 foot airstream which is awesome.

Here are my thoughts,

Is there a check valve bad (not on parts diagram)?
Is the primary oil pump slow to build pressure?
Why did the new tensioner clatter worse?

There is something up for 2011 model owners to be sharing the same issue.

kooby

I agree about the oil pump. That might be an easier fix. However, when I called my MB dealer to get a sense of repair cost, they ID it within 15 seconds of me describing the symptom as needing a new chain and tensioner. In addition, I was told that the chain is on back order. Those pieces of info put together may lead one to think that this might be a systemic issue, likely being taken care of under warranty for most.

I am wondering whether we would need any special tools for this, i.e. to pull the crank pulley (in the Hondas that I had and changed timing belts on, you needed a special socket tool to pull the crank pulley). If special tools are required, I'm gonna pass on a DIY repair given the delta in cost for an all in repair of $1,500 vs. parts of $500 + cost of special tools (plus 8-12 hours of messing around with my truck in the garage).

KrustyKustom

I read the procedure somewhere and replacing the timing chain involved pulling the LH side valve cover only. But it likely will require special tool to split the chain and reconnect it?

For 2k I think I may do it. I want to run it along time, and longer it goes the harder it is on those cam sprockets.

Menace

My GL350 Bluetec had this exact problem last week...fortunately mine is CPO, so the dealer replaced the timing chain and all is well again. They did not replace the tensioner. Vehicle only has 48,000 miles.....

KrustyKustom

What year is yours?

coldslug

Salut

coldslug

Hi guys maybe a got a clue on whats going on. Tooked mine to the my maintenance specialist yesterday. They say the rattling noise was due to a bad tensioner which is located under the alternator. Changed it and made it worse. So we came with this explaination : my old tensioner was busted out is case so its pushing on the chain further than the New mercedes one. So it could be 3 other sources for this problem: slack on chain itself, worn plastic chain sliders or the last one wich i dont want to be True, a bad sprocket ,pulley problem which can be fix only by pulling out entire engine. Today or tomorrow should be sure of what is going on.I keep you informed.

KrustyKustom

I replaced my tensioner myself with two different units, one a OEM Mercedes and a German made Febi/Bilstein. Both the rattling was worse than with the original tensioner. I compared on the bench the original with the new ones and like you said the OEM tensioner was pushed out further, actually it would come completely apart (spring etc). The new tensioners would only go to a certain point then stop.


I think it is a chain issue. At 40k there is no way the sprockets are worn and mine never made a sound until about 38k miles. Apparently changing the timing chain is done by removing the left hand valve cover, you do not have to remove the front of the engine.


Keep us "rattling" GL350 owners posted. So far everyone that has posted this issue has a 2011 model, strange coincidence?

Menace

Mine is a 2011 GL350 Bluetec. They did not replace the tensioner, just the chain. Definitely fixed the problem.

KrustyKustom

I am going to send mine in, I will sleep better without being scared of cranking the wifes car up.

coldslug

Ok guys so my maintenance specialist tooked off the entire engine with the sub craddle to gain acce s to the chain housing. YES you can change the chain by splitting it make it pass through the gears and sliders and put it back togheter but you just maybe pushing the problem to upcome further in time. When we open up the chain housing we du inspection all gears and it seams to us that all the chrome on those gears went away, exposing the metal under which starts to melt under friction. When we open it up, the chain didnt almost touch the upper double gear. A lack in chrome hardening gears cause that problem and the only way to repair it in my case was to take the engine out, because the lower bolts of the cover, thanks to MB engineering are only accessible by the oil pan! I post à photo later.

coldslug

New chain fit very tight, problem soldes dont know yet why this happen on 45k engine!