shawnmichael

I've read several posts on here about rattles in the rear but most seem to point toward interior trim pieces being loose. I have a more significant rattle that sounds like a shock. My right rear shock to be specific. Has anybody had a similar rattle/knock and what was your fix? Has anybody had a rear shock replaced without having had a rattle?

I seem to remember somebody saying that the top mount nut had come loose on the shock assembly....anybody recall?

I pulled the tire this weekend and tried to see how the shock assembly was mounted. Looks like there are two bolts holding a "mounting piece" to the truck (at the top) with a single nut holding the shock to that "mounting piece" from the top. Of course there was a single bolt/nut holding the shock at the bottom.

The shock had a lot of resistance, telling me that it's still "good" as far as shock absorbing goes but I don't think I can rule out something else, especially since the shock shaft (with the threaded end that goes up through the mounting piece) was not centered in said "mounting piece". I'm thinking that the shock shaft is what is rattling against the mounting piece....and I'm hoping that the nut is just loose and I won't need to have to spend $200+ on a new shock.

Any insights? Anybody knock the style/size of the two bolts holding the mounting piece to the truck?

At some point in the coming days/weeks I plan to remove the shock entirely and drive down the neighborhood street to see if the knock goes away. That would be the easiest way to either pinpoint it or rule it out. The knocking/rattling happens at slow speeds so I don't need to do anything crazy to verify if this works or not.

fabbrisd1

If your GLK is under new car warranty (4yr/50K miles) I would recommend a dealer look at it diagnose/fix.... I have not seen "loise" mounts in a GLK..

shawnmichael

I don't mean this to be too sarcastic, but obviously, if I was under warranty I would have it at the dealer for a suspension rattle. I've got 60k miles so I'm definitely outside my window.

I got lucky in that the other problems that I've had occurred under warranty (timing chain tensioners, wheel bearing, repeatedly blowing 12v auxiliary fuses, auxiliary battery relay) but I've already had brake/rotor problems, a CEL (Evap Emissions systems leaks) and this suspension rattle that are all not covered.

I love to hear people ignorantly talk about how good MB is and that you have to spend money to maintain these high performance machines. What they fail to admit to themselves is that these are repairs, not maintenance. A person should not have to spend this much effort, time and money to keep a 2013 vehicle running in 2015.

shawnmichael

Ok, so I made some progress last night.

I removed the shock like I said I was going to and drove around the block. NO NOISE! So the problem is the shock. But...I would hate to buy a new one and put it on and realize that it's more of a design/mounting problem than a shock problem. The shock is still extremely strong. That tells me (as an electrical engineer) that the shock is still good. Any insight? Can the shock be bad and rattle if the shock is actually still good? Should I try insulating the mount from the body with a piece of rubber or is there any likelihood that that would fix anything?

I also took some pics just in case somebody wants to know how to disassemble. Holy crap there is a lot involved with just removing a shock. The passenger interior trunk trim pieces all need to be either removed or loosened just to get access to the two nuts holding the shock to the body. Lots and lots of nuts, bolts, clips, etc.

NYCGLK

sorry to hear that...I think there are always bad apples with any manufacturer. If had problems like you, I would have sold the thing and moved on. Mine is 6 years old and the only warranty work I had was dead command screen. Your experience is not the norm.

cottager777

I had the same symptom and had to have the right rear shock replaced under warranty. They could not find any part of the suspension that might cause the noise so by default they replaced the shock and the noise disappeared.

shawnmichael

That's good to know, thanks for contributing. While it's possible that it could have been a bad pothole or something over the years that led to this, I would venture to believe that I'm not the only one who's had to replace a shock. It's just hard finding the people who have.

I read one other post somewhere about a guy who had a shock replaced but it didn't work. So even though I already bought it (from Tire Rack) and have it sitting in my garage, I've been a little leery that it wouldn't work.

vandygrabass

shawn/folks -

wow, I am having this exact issue right now. bought a 2011 CPO with 42k miles 3 weeks ago. started noticing a rattle from rear but only at slow speeds, really. I took it to my dealer yesterday and he called today and said it is the - get this - right rear shock. wow, so what's up with the right rear shock specifically??

problem is, my dealership said shocks are not covered by CPO. shawn, my advisor's assessment fits your assessment - he said the shock itself is fine, plenty of life left, not 'broken', per se, but that something in the shock is making this noise. to replace would be $640.

i'm currently in contact with the mercedes dealership from which I bought this CPO from a few weeks ago as the CPO checklist specifically mentions shocks/struts as something that is supposed to be checked during certification.

will let you guys know what happens...the good news, I suppose, is that the noise itself is not awful and is only an annoyance and the shock is still perfectly functional.

but again, why the right rear specifically for all our cases?

shawnmichael

Thanks for posting. I'm glad to know that I'm not one of only a few who either had the problem or told people about it. Unfortunately, I think most people blame themselves when their expensive cars break because the alternative (that we made a bad purchase) is worse to think about. That being said, I sold mine two weeks ago and got a new Lexus GS 350. So I can provide insight, but I can't go back and look at mine.

So... I would definitely recommend fixing it yourself if I were you (and the dealer declines to fix it). I bought the shock from Tirerack.com for about $90 and it took about 2 hours tops to install. It requires removal of the wheel and wheel well liner, and removal or loosening of most of your passenger side interior trunk panels. But it's not that hard, you just have to find the snaps and screws/bolts holding everything on. 2 hours and $90 is a far cry from what the dealer wants AND you learned a valuable lesson...Don't assume just because a car is more expensive than another that it is better quality. I can't tell you how many people have said to me "it's the price we pay for the privilege of driving a Mercedes Benz". That's BS!

Now for some insight into why/what I think the problem may be. There is a mount piece at the top of the shock assembly that the shock shaft attaches to (with a single nut). That mount piece has two studs coming off of it that go up through the truck chassis/body and get held on with two nuts from inside the trunk. At the top of that mount piece is a very thin piece of rubber integrated into the mount. I "think" that rubber piece is supposed to prevent knocking/rubbing on the chassis/body and after a couple years of wear, simply fails to do so. Once it compresses and/or wears down enough, you have a metal on metal contact point. But I could be wrong. That being said, I put a washer on those studs BELOW the chassis/body which ensured that when I tightened the nuts down there would be less chance for play between the chassis and the shock. I felt that there was a chance that the nuts were not fully seating/pulling on the studs and (since the rubber was worn/compressed) it was allowing the mount piece to rub against the chassis/body. When I put it all back together...voila! No knocking at all. If you choose to do this also, I made sure that I found washers that were just big enough to fit over the studs. I didn't want to have any play in those washers or I risked having them moving around also.

Now that I've said all that, you could probably just pull the top of your shock out (only one bolt holding the bottom on) and install a piece of rubber (Lowes sells a 4"x4" piece of rubber that is probably 1/8 to 3/16 thick that would work perfect) cut to exact dimension of the mount and install it between the mount and the body (cutting holes for studs). If my theory is correct, that should prevent the knocking noise between the mount and truck body. The second picture that I attached shows the mount studs better. I can't find a picture that shows the mount from the end (with the rubber). It's possible that you could fix this problem by replacing the mount with a new one (with fresh rubber).

Rascally Wabbit

I have the same rattle as posted by others & will try to resolve it this week. This link displays the parts involved. Item #40 is the focus or perhaps the cause of the noise.
http://www.mbpartsworld.com/showAsse...driveLine=9984
Wondering if anyone who has had the shock absorber replaced by the dealership also had item #40" replaced too. It is described as "bearing" but from the comments it is not a bearing but load bearing perhaps. Looks to me that MB complicated this by adding the extra piece. Many vehicles (not strut type) with a shock absorber & a bayonet attachment at the top simply have two rubber bushings & 2 plates which are mounted one of each above & below the sheet metal where the shock is attached. Wonder if there is a TSB out on this. Any & all comments are appreciated!

shawnmichael

You are correct, that is the culprit. I wouldn't recommend purchasing it because simply adding washers fixed my problem. Lowe's sells a 4" x 4" sheet of about 1/8" (maybe 3/16") rubber. I think they stock it in the plumbing section. It would make a great buffer to add where this mounts to the body.

Rascally Wabbit

Finally got around to tackling this rascal. Removed the RR shock absorber from the GLK. No signs of anything rubbing on the body around where the bearing plate mounts & none of the nuts were loose. Incidentally this bearing plate does not contain a bearing, is only load bearing between the shock absorber top mount & the unibody. The bearing plate has two studs which mount it to the unibody. The studs are threaded for their full length. The upper rubber face of the bearing mount appeared to be scuffed. Shock absorber action was very stiff & a challenge to compress when it came time to reinstall. Went ahead & purchased a 1/8" thick sheet of rubber from the local hardware. Cut three holes, two for the studs & one for the shock absorber stem in the rubber. Placed it on the mounting plate so it is between the mounting plate & the body, tightened all the bolts secured further by blue Loctite. Results are the rattle has changed, sounds muted but still present. This tells me that the problem is either in the shock absorber itself or some where else in the rear suspension. As to why it affects the rr shock absorber only, my guess is that it is the axle which applies the motion & torque under most circumstances. IF you decide to tackle this yourself, the top stem of the shock absorber internally is a 5 MM hex to facilitate the removal of the top nut. Any further comments or questions are appreciated!

Rascally Wabbit

No comments yet so here is the next step for me. Likely it is something about the shock absorber but to ascertain that it is, the next step will be to swap out the shock absorbers from left to right & see if the noise moves. At this time I will remove the rubber piece which I installed & as mentioned changed the rattle. Have more time than money (retired) so I will tackle the job this next week. No delays!

lyonkster

I have had the same rattle for years (right rear), which no one has been able to diagnose. This thread motivates me to look again, maybe start by disconnecting the rear shocks and see if the noise goes away.

Rascally Wabbit

The rattle has to emanate from some where. Very strange that the shock absorber action is very stiff, no sign of an internal failure or for that matter any exterior sign of leakage. Hoped to start on this but now delayed due to the "CEL" light has illuminated.

LiftOff

Any updates regarding this?

I have noticed a sound coming from the rear of my GLK as well.
It only happens when driving at low speeds or going over some bumps.
I can easily produce the sound by putting the car in reverse, backing a little and then switching to drive. As soon as I tap the breaks when moving forward, I can hear the noise.

I'm thinking it might be a bad shock...

AzCamel

From previous suspension work on other cars I am going to say the top hat is the issue, luxury cars tend to use softer rubber that wear exceptionally faster then normal economy cars, it's a give and take between comfort and longevity. I would look at replacing just the top hat only instead of the whole shock assembly.

LiftOff

Would you recommend adding the extra rubber piece as others have done, Or just ordering a replacement "top hat"?

AzCamel

Adding the rubber piece is a bandaid and will depend on the density of it your better off adding a layer of urethane which is harder and will last longer, they are much harder to find. The issue I see with doing that is you might lose some of the "comfort", it will stop the rattle but will also transmit more vibration. IMO I would just replace the top hat and use blue locktite on the bolts, from the post the above it seems the Bulls and bolt gets loose over time and cause premature failure.

louiet3

@AzCamel, are you referring to item #40 mentioned above as the top hat? Thanks.

AzCamel

yes the top hat is#40, but Mercedes also use soft rubber for the spring seat so you might consider changing that also if the price is cheap.

AzCamel

I would if it is cheap enough, take it apart and inspect it for play and cracking. BMW and MB print seat are soft and wear faster

louiet3

Would items 150 and 170 be the spring seat you referred to?

AzCamel

yes

Rascally Wabbit

So now a year later- where did the time go? There were a couple of issues on our GLK so wife decided to throw money at it (her car) as I had not taken the time (interest?) to delve back into this issue. Went with a private reputable shop whose rate is $101. per hour. I explained that I had added the extra rubber piece at the top with no change in the noise & was not certain it was the shock absorber. The metal plate at the top is just that, more an adaptor than anything. When tech removed the rt. rear shock absorber, it was found to have a small amount of free movement when depressed before there was resistance from the shock itself. Had both of the rear shock absorbers replaced & all is quiet. So from my experience the issue is the shock absorber. I would have preferred to swap out the rear shocks left to right etc. to see what would happen but did not. Interesting that the one which failed is the one on the drive side which takes imo more stress.