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Thumping noise during drive

17K views 38 replies 10 participants last post by  James Whitaker 
#1 · (Edited)
Suddenly (like thunder from clear sky) the car gave me a present: thumping noise during drive. If i put in N during the drive, situation is same.

Noise is not strong but i can hear it.
frequency of "thump", "thump" ... is proportional to rotational speed of wheels (car).
loudness is not dependent on the speed.
I checked each wheel and they all spin freely without noises. no free play in wheels.
In rear wheels test (car on stand) i was focused also in drive shaft, however I did not hear any noises from it (which of course does not tell much, i cannot rotate wheels fast by my hands).

1) Flex discs?
2) Drive shaft bearing? How to check drive shaft bearing when car is stationary?
3) unbalanced tire? but i do not feel vibrations. i did not drive more than 70 km/h.
Thanks,
Samo.
 
#2 ·
The flex disk and center carrier bushing are the usual suspects. Pay close attention to the front disk. If it's bad and let's go, it isn't fun. Sitting on top of the transmission tunnel, directly above the disk is the airbag control module....

A 124 member here in Florida had the front let go while at normal speed. The resulting bag deployment and tunnel trashing wasn't pretty.
 
#5 ·
I had the same issue when I first purchased my car. It turned out to be 2) Drive Shaft Bearing. There was no way to check it without taking the exhaust out from the headers back. Then you could see down the shaft to the bearing.
I had to remove the entire drive line, from the transmission to rear axle (flex disc to flex disc), to replace the bearing. It sounds harder than it is, but it did take me all day to complete. And, the only special tool you need is some type of press to remove and reinstall the bearing itself.
 
#9 ·
That looks toast, I think... how long did it take you to get to that point, to be able to see the center support ? I just got a 97 s600 will probably being putting ...this on the list
It took about 2.5 hours to get to that point. That's removing the exhaust system from header joint back to the tail pipe, the center heat shield and rear transmission support.
 
#10 · (Edited)
thanks for your inputs gentlemen.

as i wrote i will check things today. first, is it clever to put car on stands and "drive" it with wheels above the floor? Maybe i can simulate driving conditions but i doubt because the weight of the car will not be involved in equation.

secondly, i hope i will be able to check free play at center support. i guess if i will find any, then it is clever to replace bearing and support (i am talking about something which i did not touch so far so excuse me my ignorance). In another words i imagine that there is a bearing and something which holds it (i have alldata.diy do not worry :)). So i assume something is wrong with the support not the bearing itself. bearing would probably give whining or grinding and not thumping.

P.S.: i can see from alldata.diy that bearing support is called "rubber mount". I am pretty sure it is dead. maybe i can risk in order to simplify the repair and replace only rubber mount. in theory bearings can stand a lot of working hours so most probably it will be fine. if it is easy to replace it, then i will do it.
 
#11 · (Edited)
thanks for your inputs gentlemen.

P.S.: i can see from alldata.diy that bearing support is called "rubber mount". I am pretty sure it is dead. maybe i can risk in order to simplify the repair and replace only rubber mount. in theory bearings can stand a lot of working hours so most probably it will be fine. if it is easy to replace it, then i will do it.
If you have this many KM on the car and you've never replaced it, probably you'll find no rubber left.

Indeed, it is called rubber mount and I was scolded for using this very same terminology some time ago:

http://www.benzworld.org/forums/w140-s-class/2577073-1404100481-rubber-boot-bearing.html

Steve

PS 2.5 hours is overly optimistic for the DIYer with no prior experience. Exhaust must be dropped and it took me almost 2 hour to accomplish this.

PPS It can be argued that if the flex disks are original, now is the time to replace them as well.
 
#12 ·
i checked situation:

1)flex discs are like new. coincidentally not so long ago they were checked by expert who worked 40 years on transmission at MB dealer and he said they are totally ok. but anyway, i checked them.

2) i do not have any experiences about how stiff the rubber mount must be. that is a problem now. Visual check showed that rubber around bearing is in one piece and there is no free play when i moved the shaft by hand. if i move it with screwdriver at position of the support then the shaft moves a couple of milimeters. i do not know if the support has its initial stiffness but for sure it is not extremely bad. maybe it is bad but for more accurate diagnose i should remove the exhaust. can someone tell me if some free play is ok? it is free play due to rubber not due to air.

3) at the front flex disc the sound insulation rubbed against the flex disc (bolts). it seems there are plastic clips from inner side of the insulation and they are broken. there is also some plastic incorporated into the sound insulation foam and this plastic definitely had a contact with bolts on the flex disc. consequently a rhythmic "thump" "thump" noise is logical.

conclusion:

i made 3 holes with screwdriver and glued the sound insulation to the chassis through them. i must wait several hours now and i will check the situation then. this of course does not mean that my rubber mount is ok, but i guess i can leave it if the sound will be eliminated? i think it cannot result in so big damage as if flex disc falls apart. please comment.
 
#14 · (Edited)
once again let me say that visually i did not see any missing rubber or so.
Unless you are looking at the rubber from the correct angle (i.e., looking down at it), you won't be able to see any cracks. Doing what the video shows only tells you that you have some lateral movement, which probably doesn't mean much since this is expected.

Check my pictures -- I had only 50,000 miles on mine when it was replaced. Rubber was hard and cracked.

Steve
 
#15 ·
first, sorry for my stupid expression: "once again let me say that VISUALLY i did not SEE any missing rubber or so."

...of course it is visually if i looked it :).

I will check your pictures and yes, the angle under which i can observe the support is far away from ideal. it is cold outside and glue is curing slowly, most probably i will let it over night, so hear you tomorrow.
 
#16 ·
Samosali,

First let me say that per your profile, you have nearly a quarter of a million miles on your vehicle, that is a lot of revolutions of the driveshaft center support bearing. Next your vehicle is 24 years old that is a long time for rubber especially under load. Lastly, the center support bearing is really only inspectable with the driveshaft out of the vehicle and I can guarantee that the bearing is shot. If your spin it in your hand you will hear the noticeable bad bearing. Next the center support bearing rubber mount is also really inspectable upon drive shaft removal. The alignment of the shaft angle is critical and the rubber mount usually fails by its sagging due to compression, you will see this as an unsymetrical mount (not round), or by cracked, dry rot or torn rubber. Yes there is labor in the removal and replacement of the driveshaft but not terrible to do and the parts mentioned above are not expensive purchased front on line MB dealer source.

SKG is the OEM for the flex disks, are yours OEM or some knock off brand? Do you know when they were changed e.g. mileage and time?

Upon changing out the aforementioned parts you will notice ride quality of smoothness and quiet will be quite noticeable.

My 2 cents. Hope it helps

Seth
 
#17 ·
Seth, I know :). I mean i can imagine that my rubber support is not healthy any more. I am not so sure about the bearing but anyway i agree that once I am there I will replace it.

But .... i tell you that it is not so bad based on what I have seen yesterday and I hope it can wait until spring when weather is fine and work on car is a joy. Now it is raining and it is cold, soon will be snow. Definitely it is on my list. may I ask you if removing of rear part of drive shaft is enough or i must remove both parts?

All what i wrote can change in next hours when I will drive the car. If the sound will go away than I am good. If not, I will replace central support ASAP.

BTW, I studied internet and found out that some moving (ca 6 mm) at the rubber mount is ok. if we think a little bit, the central support is there to enable some moving of the drive shaft. This is not supposed to be exactly on one place.

I am not sure if you are suggesting me to replace flex discs, too? Even if they look like new? Seriously, they are even not dirty, no cracks, no deformations, no strange changes of color on the surface, etc. They feel pretty soft if I touch them with non-sharp screwdriver. They are original MB parts and they were not changed in last 10 years and in last 120.000 km. I do not know the previous history.

Look, when we decided to drive these cars we actually signed a contract that we "wish" some troubles and that we do not wish peace. I mean, there is at least 100 pretty critical parts on my car which are worn and should be replaced. and another 1000 parts which would be nice to be replaced. So what to do? Then i rather buy a new car and problem solved. However, if i notice one little smallest crack in the flex disc, then I will replace it in the middle of the night to be completely clear.

Thanks in advance for your comments, i am always curious about what other people think and how they think.
 
#18 ·
Update: no more thumping noise. it was definitely sound insulation lining between the shaft and chassis. not foam itself but some plastic parts on it from inner side, i guess once they were clips for fixation. slowly the foam rubbed into the flex disc and it "grinded" it to the inner side (plastic).

central support is on a list. in comparison to broken flex discs, how dangerous is to drive with semi-functional rubber support?
 
#19 ·
"may I ask you if removing of rear part of drive shaft is enough or i must remove both parts?" - I had removed the entire shaft per WIS but I would expect you could just remove the rear. Just be triple sure to mark the 2 shaft PRIOR to disassembly since they are balanced from the factory. I am sure once you spin the center support bearing in your hand you will hear that it is dry as a bone and it is only 13 bucks OEM per my recollection. Another advantage of removing the front shaft is the ability to re-lubricate the center locating pin going into the transmission.

"I studied internet and found out that some moving (ca 6 mm) at the rubber mount is ok." - Yes of course it is supposed to move it is soft rubber. What I am referring to is the nominal alignment which is critical for the universal joints to prolong their life. It is obvious when comparing a used high mileage mount to a new mount e.g. the compressed mount at the bottom e.g. not centered symetrical. you can see this prior to removal.

"I am not sure if you are suggesting me to replace flex discs, too? Even if they look like new? Seriously, they are even not dirty, no cracks, no deformations, no strange changes of color on the surface, etc. They feel pretty soft if I touch them with non-sharp screwdriver." - No I am not suggesting you change them only verify them. Actually they are not completely inspectable (both sides of the joint) only the surface facing the driveshaft and you need to to "load the joint" to ascertain if cracked which is different from relaxed condition. If OEM the fronts usually last 100K miles the rears usually last 200K miles but that is average based upon temperatures and driving load.

I do sincerely wish you the best of luck with your maintenance, repairs and driving joy

Seth
 
#20 · (Edited)
"may I ask you if removing of rear part of drive shaft is enough or i must remove both parts?" - I had removed the entire shaft per WIS but I would expect you could just remove the rear. Just be triple sure to mark the 2 shaft PRIOR to disassembly since they are balanced from the factory. I am sure once you spin the center support bearing in your hand you will hear that it is dry as a bone and it is only 13 bucks OEM per my recollection. Another advantage of removing the front shaft is the ability to re-lubricate the center locating pin going into the transmission.

Seth
Seth:

In my response (#11 here) I have the link to my thread.

http://www.benzworld.org/forums/att...100481-rubber-boot-bearing-center_support.jpg

I concur that removing the whole shaft is the way to go. Not even sure one will get enough clearance in the back to undo only the rear half....

My bearing after 50,000 miles was snug and quiet, but the rubber mount was cracked and extremely hard. The boot was also shot.

The bearing is indeed not expensive, the mount is pricey and one needs to pay attention to the EXACT part number. I ended up buying two mounts -- my fault entirely because I had incorrectly assumed that C140 -- S500 and S600 -- will be the same, but they are not.

Steve

PS The OEM bearing is likely SKF re-packed in a MB box. Made in Slowakia for what it's worth (Samosali likes to point out the MB parts originating from Eastern Europe.... :)
 
#21 · (Edited)
Seth, Steve, thanks. Seth, please could you explain in one sentence only what is "center locating pin" which is going into transmission? Is it something which points out from the middle of the front drive shaft?

beside a rubber support I should buy a repair kit (bearing, boot and two protective caps)?

Samosali likes to point out the MB parts originating from Eastern Europe.... :)
because it is funny. 30 years ago engineers from MB even did not know where Slovakia is ... :) And today almost everybody do not distinguish between Slovakia and Slovenia.
 
#22 · (Edited)
Seth, Steve, thanks. Seth, please could you explain in one sentence only what is "center locating pin" which is going into transmission? Is it something which points out from the middle of the front drive shaft?

beside a rubber support I should buy a repair kit (bearing, boot and two protective caps)?



because it is funny. 30 years ago engineers from MB even did not know where Slovakia is ... :) And today almost everybody do not distinguish between Slovakia and Slovenia.
1. No, the 'pin' IS the the end of the output shaft (very back of the transmission).
Please see here:

http://www.benzworld.org/forums/w14...ailure-tranny-rebuildable-2.html#post13830698

The front part of the prop shaft slides in there . Look it up in your EPC -- there is a bushing (press fit) in the prop shaft.

2. You need the center support, the boot, and the bearing. Check carefully my thread at you'll see the three parts.

3. To the long list of MB parts made in Eastern Europe, you can aslo include the Bosch F8DC4 plugs, made in Russia (some discussion on that here: http://www.benzworld.org/forums/w14...you-s600-front-ads-shocks-2.html#post15044697). And of course, not to mention the infamous 'biodegradable' engine harness (what a joke, MB just got dupped by their supplier) made approx. 50 km away from a place I used to call home... :))

Best regards,
Steve
 
#23 ·
1) Flex discs?
2) Drive shaft bearing? How to check drive shaft bearing when car is stationary?
3) unbalanced tire? but i do not feel vibrations. i did not drive more than 70 km/h.
Thanks,
Samo.

Possibly neither of those items???

What I have found here in Sunny California is the sound/heat transmission tunnel insulation pad is falling on the yoke/flex-disk/drive shaft.

When it cracks off the insulation pad resembles a like a hard composite roofing shingle found here in the American Roofs..

Get under and check it out....

Ahhh Check to see if the yoke nut is still in place as Joe had the nut disappear on his S600

Martin
 
#24 ·
Thanks Steve. So biodegradable harness was made in Eastern Europe? that was really something ... :(.

I drove a car today and the thumping sound is actually here (again). The non-fixed sound insulation was evidently not a real culprit. all is clear regarding center rubber support replacement but i would still like to be sure what is going on. Here is description: the sound is loudest at ca 30 to 40 km/h (ca. 20 mph) and below. I do not feel any vibrations. it is soft sound "thump" "thump" "thump" ... like when you go over the frog and it stays on the tire ... I cannot hear anything above 50 km/h.

Any ideas? Thanks.

Samo
 
#25 · (Edited)
Possibly neither of those items???

What I have found here in Sunny California is the sound/heat transmission tunnel insulation pad is falling on the yoke/flex-disk/drive shaft.

When it cracks off the insulation pad resembles a like a hard composite roofing shingle found here in the American Roofs..

Get under and check it out....

Ahhh Check to see if the yoke nut is still in place as Joe had the nut disappear on his S600

Martin
yes i thought it is sound insulation too but it is not. the sound is still here (see above).
Can you please explain a bit more this about "yoke". What is it, where is it, i have no idea what you are speaking about. Is it a nut on the drive shaft close to the joint? If so, I must admit that i do not know why is it for. is it necessary to loosen it in order to get two halves of the shaft out?

Samo

P.S.: i did not do my homework yet so i did not check Steve_B's thread (yet).
 
#31 ·
gentlemen, thanks for your explanation about "yoke". We actually translate such things as a "flange" here. Never mind ...

please somebody tell me that i can use graphite grease (maybe some another one available in normal stores) for heavy conditions for bearings for every part on the propeller shaft (sleeves, splines).
 
#32 ·
please somebody tell me that i can use graphite grease (maybe some another one available in normal stores) for heavy conditions for bearings for every part on the propeller shaft (sleeves, splines).
Samo,

Obviously we are all free to slop on any grease we care to gooop on... But? If you want the CORRECT grease, these are the "Specified" Lubes:

For Centering Sleeve: MB 267.0 - Multipurpose grease (NLGI Class 2, Specification 267.0) - Mercedes-Benz Specifications for Operating Fluids

For the Sliding Splines: MB 266.2 - Long-life grease (NLGI grade 2, Specification 266.2) - Mercedes-Benz Specifications for Operating Fluids
 
#33 ·
Thanks Patrick. regarding lubricants I am really careless. Ok I am very mindful when transmission, engine and brakes are in question, but for other things I am inclined towards "universal" stuff, escpecially because chemistry is my weak point :).
 
#35 ·
i checked once again the center support. this time i removed heat shield and i got pretty good access. the rubber mount looks totally ok. no missing portions, no deformations. i checked it from both sides and 360 degrees around. yes, if i apply a lever, i can move the bearing for several millimeters but the design of the rubber support seems to be (initially) very weak. I mean, engineers evidently did not plan to make this portion of the shaft super stationary. if they wanted it so, then i assume the rubber support would look like several centimeters long piece of rubber ..but the whole thing reminds me more on diaphragm than on any "serious" rubber support which must endure enormous forces.

Another thing is that my rubber support is actually very soft, I would expect hard cracked rubber. So excuse me all those who expected that my rubber support should be bad after 24 years and almost 400,000 km. I dare to say that it looks almost like new. do not know if it functions like "almost new". I would like to hear how rigid actually the support (rubber) is when it is new.
 
#36 ·
Another thing is that my rubber support is actually very soft, I would expect hard cracked rubber. So excuse me all those who expected that my rubber support should be bad after 24 years and almost 400,000 km. I dare to say that it looks almost like new. do not know if it functions like "almost new". I would like to hear how rigid actually the support (rubber) is when it is new.
Well, Samo, I also "thought" my Flex Discs were ok, despite 300.000 Km... But? As you can see from my post, the Discs were in MUCH WORSE condition, than what they "Appeared" on Inspection.

Now, I'm not Implying your discs are bad... and I'm not saying the Discs are causing your symptoms...

All I know is: Replacing mine made a WORLD of Difference! Much, Much smoother Drive.
 
#38 ·
Well, Samo, I also "thought" my Flex Discs were ok, despite 300.000 Km... But? As you can see from my post, the Discs were in MUCH WORSE condition, than what they "Appeared" on Inspection.

Now, I'm not Implying your discs are bad... and I'm not saying the Discs are causing your symptoms...

All I know is: Replacing mine made a WORLD of Difference! Much, Much smoother Drive.
I am aware that new is new and old is old. it is just a question of balancing between putting all my fortune in this car and make it close to perfect OR fixing only those things which are really annoying and/or dangerous. I decided for latter. Because there is no visible cracks in flex discs I will keep them. Maybe PO replaced them and they are let's say 15 years old, not 25.

New rubber is MUCH SOFTER. Old rubber may look fine, but will be w/o its elastic properties. This is why cracks develop and shortly after the pieces will start falling out.

Accidentally, this is why tires that look new, but are more than 8-10 years old do not stick well to the road (RIP Paul Walker, the 2005 Porsche Carrera GT that he was killed in had its original tires -- Paul Walker's Porsche had outdated tires at time of fatal crash - latimes)
i am really shocked to see my rubber support sooooo soft. like i indicated above in my answer there is a chance that this part of the car was replaced in this century. this is supported by the fact that heat shield screws are evidently worn. i agree about the tires. to me 6 years is maximum. I did not know that fact about Walker, had no idea that tires played a big role in his accident. RIP.
 
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