atom-ant

Hi Guys,

I am getting a strange whine which is not consistent as a proper worn-out bearing but does feel like a bearing - I think! - It is driving me mad!

It is coming from front somewhere however there have been occasions where my natural stereo system fails to identify if the noise is comming from left or right. One thing is certain when I turn left; the noise is more obvious and does feel like a duff bearing - no noise when I turn right.

Today I jacked up the car, pushed the brake callipers a bit back so there is no disc pad friction music and spun each tyre starting from front right (suspect) since I thought I'd hear something. I was shocked to find there was no noise at all and the all four wheels including front right spun quietly. The front ones (both wheels) however would keep rotating for a while (could be loose bearing lock bolt the one with hex ?). There is negligible free play if I move the wheel when holding it from top and bottom.

I have brand new set of Dunlop SPORT MAXX RTs so it cannot be tyres since previous ones few weeks ago had exactly similar noise.

I am annoyed that I am unable to identify this sound. Even tried shifting to neutral and switching off the engine (on a safe road) to rule out it is not transmission or axles but noise is there...

Any advise / help would be highly appreciated.

thanks in advance.

CGSColin

It could be one of your front CV joints. The fact that it happens when you turn certainly points to it. One obvious sign would be if one of the rubber boots covering the joint is damaged and let dirt and debris into the bearings. Even if the boot isn't damaged it could still be the joint though.

Carsy

CGS, The noise is from the front on a rear wheel drive.

Try a stethoscope on the wheel bearings when jacked up & rotated.

If the noise is evident at low speed have someone cycle/run beside the car to ascertain which wheel!! It is not as silly as it sounds.!!

Also a wheel could be bent slightly , maybe change front to rear to check.

CGSColin

Doh, I missed the part where it wasn't 4matic. My bad!

atom-ant

Thanks guys, so far I have been unsuccessful. Went to a local garage just to get them checked if it is a wheel bearing and if so which one. I definitely know it is comming from driver side front or rear (UK right hand)
so the garage failed to find any issue with wheel bearings. There is no free play nor a whine was heard when all four wheels jacked of and hand spinned. They said come back when noise gets worst ??? The moment he said this i left the garage...

So taking mater in my own hand again. I am going to replace the front and rear wheel with the thinner spare wheel in the boot at a time to identify if it is a wheel rim or whatever.

All cv boots etc etc looked healthy.

The noise starts at 21mph.. more vocal at 33mph then it disappears at 50-60. When turning at sharp bend on left only ( at 30-55mph) i can clearly hear a griding noise. The noise on straight road is not consistant grinding in fact sign wave type low high pitch patern. I will see if i can youtube it some how.

The issue if when i turn left it is so difficult to identify that grinding noise; if it is front or rear.

Open to more ideas.. thanks once again.

atom-ant

Rear Right (Near side) bearing it is after all of that hunting around. seems like not a DIY home job compared to front ones!

atom-ant

I feel like kicking myself after spending the time and money on the rear bearing that was in fact not faulty and was utterly misdiagnosed by 'me'. How will I sleep tonight.

The irony is that I have spent money on RHD front and rear bearing and the howling is still there. I am now thinking it has to be Diff ( I have learnt an expensive lesson so even if it takes months to diganose I'll now take my time). Luckily I didn't use merc labour else I would be in utter depression for a long long time. The cost of both front and rear bearing was 176£ OE ( The parts which did not need changing AT ALL). How can I be such a Minion. The mechanic is my friend who was happy with a bottle of red wine. I just cant believe the howling is still there!

The rear one had to be pressed 50 mins job hangs on with for bolts from inner side of hub. Front was literally 20 min job. few photos attached.

Since the whole scene is changed. What could this noise be ?

My mate (with red wine) did not test drive the car before we changed parts (he trusted me though he said things look ok, but i insisted!!!!)
He is advising changing diff oil. I am now sceptical about everything! to the level that I can declare my self to be paranoid!

BTW the noise is still there howling turns to grinding when I turn left.

Carsy

My car is susceptible to picking up stones which lodge between brake disc & disc steel protector. It makes a terrible sound & changes when turning.

I said before if the noise is evident at 20mph have someone cycle beside the car.
Changing the diff oil is a cheap option, at least check the diff level & quality of oil ( any metal ?) . Also you could remove the back seat to give you a clearer idea of diff or rear axle joint noise.

To me the most likely cause from your description is a rear axle joint.

I have attached a few diagrams which may be of use.

Good luck & keep us posted.

atom-ant

Thanks @Carsy. So the axle joints can still be shot eventhough the boot seems ok and there is no sign of grease arround it ?

Carsy

That is a possibility . If you partially remove the boot you may be able to find evidence of metal in the grease indicating wear.

Removing the back seat is an easy option to see whether the noise increases.

atom-ant

An update, sofar I have been unsuccessful. Tried removing the rear seats. So the noise does get more prominent and I can sort of tell it is rear mid right handside-ish.

One observation, when the car was jacked up I observed the part Number A2043500172 item 80 in diagram to be loose. By loose I mean the rubber mounts are loose and weak, you can easily move it by hand.

What will be affect of this part on being faulty. I am trying to rule out everything here.

Carsy

That is a Vibration Absorber . If the mounts are worn then that could produce a noise .

They could be loose and not under tension when jacked up ?

How many Km has the car done ? . They should not be worn unless high mileage or rough conditions.

Is there any metal on metal?

atom-ant

Sorry was away on holiday (driving UK > France > Belgium and back) that insane noise has neither increased nor reduced
I am removing the CV boots next weekend starting from driver side rear axel shaft to assess damage ( If I can spot any). I am not giving up. I love my car, we'll get there in the end!!!

Re: Vibration Absorber - it is just loose as one of rubber has decayed there is no tension (metal on metal) i.e. the main mounts for diff are solid. The car as of today has done 136K Miles. I bought the car at 21K (not 121K) and all the millage I have done is just motorway miles. The car is not cheap to run in city (start stop driving)

Will feed back once I have examined the axels.

Carsy

Interested to know what you find.

I would think about renewing the vibration damper mounts . They will not be doing their job & maybe that it the cause of your noise?

C300Sport

I agree with you Carsy. As tight as the tolerances look to be around the damper, it could set up a bit of a resonance/rub in certain situations...tracking down things like this can be maddening.

atom-ant

Thanks guys - will replace the mount soon - has to be done.
Been very busy so have not done the big operation yet (i.e removing boot covers). however I did a quick test,..

I jacked rear one side at a time. (so one wheel in the air - the side that was being tested) had to switch ESP off.
Rear right when jacked and wheel spinning in idle 1st gear seemed absolutely normal.
Rear Left when jacked and wheel spinning in idle 1st gear ( I get faint rumble.) If I touch the rear wheel arch I can feel harmonic vibration. I even tried a car stethoscope but it did not yield any result.

So I removed the rear seat (base and damping foam) and the noise got a but more noticeable. So it is under the fuel tank rear left between the Diff and the hub (axel area)

I can only think of rear left wheel bearing that is the only part left lol that is not changed yet.

2 weeks ago I also change the diff oil (blo%%dy expensive) 30£ / per litre/bottle (hypoid original Mercedes) took 1.2 litres. The drained oil was clean; no fillings or shavings on the magnetic bolts. So diff is ruled out - To double ensure I checked the diff with stethoscope at various speeds when car was jacked.

The funny thing is that the noise is prominent ( turning left - loading right side) it should be the other way round as growling feels from rear right when driving but my test revealed growling from rear left. I think this rule does not apply my merc lol.

I am living with it but not letting go.

Carsy

Thanks for the update. You are getting it into a corner now. Left CV joint or wheel bearing ?

Keep us posted.

atom-ant

FYI - still living with it. Have not got time yet to fix. will update soon.

Rickynoman

Hey All,

I don't know if you have figured out the solution -- but I had a noise that was driving me crazy -- and it seemed to be coming from the same place you were mentioning.

It was a grinding noise, and I could only really hear it when I was in underground garages, or on the road at night when there was little noise.

It turned out to be the alternator. The alternator was fine, but apparently Mercedes alternators, and all other motors on the serpentine belt have a chip in them that cut power to them when in straight aways to make sure all power is to the wheels. then, when you let off, the alternator gets surged to repower all these motors (a/c, power steering, etc.). the problem is that eventually the alternator gets tired, and starts to whine. It still performs well, but gets loud. sounds almost like an electric motor. The weird thing is that the draw and power levels are all where they should be... so a mechanic won't be able to diagnose the issue with traditional meters. Have them change it out -- you'll be pleased!

try swapping the alternator to see if the noise goes away -- I did and it worked. now every time i hear a W204 go by with that noise, I tell them to change the alternator if it annoys them.

atom-ant

Happy New year all.

Thanks @Rickynoman. I am still dangling with the noise issue. for me it is certainly not the alternator. It is the prop shaft bearing. I am waiting for it to get worse (not blow) to make sure the diagnostic done by an a new indy is again not incorrect.

Rickynoman

Happy New Year to you as well!

Gotcha! well as long as you know the problem, then you can figure out the solution.

Just thought id post my experience with the alternator because it was an odd issue that yielded an annoying noise, that was hard to diagnose, but very simple to fix!

Best of luck!

kodpkd

Bearing noise is very hard to diagnose. You can't tell if they are bad by looking at them, unless you taken them apart and actually look at the individual roller bearing, or ball bearing. A sealed bearing when not under load feels perfect. If you jack up the car and listen, even a bad bearing wont make noise. I have tried to use an auto stethoscope. If the sound seems like it is coming from the right side, it probably isn't. It is the opposite side. Good luck

atom-ant

Hello Again. I personally do not like threads where there is no solution or end. Happy ending is always better. On that note I would like to thank everyone especially @carsy for helping me diagnose / sharing ideas schematics etc.

My car is now fixed. Problem that started in july 2015 got fixed in Feb 2016.
It was propeller shaft bearing which was the culprit. I wasted a lot of money here and there but cant complain! expensive learning

Yes it was a bearing but not the wheel bearing nor CV joint or the differential. It was clear that the noise was in mid section, there was no real vibration etc which could have helped in root cause!!
So if your car has weird noise then persevere and take your time before you start changing parts.

My car is super quiet now yet that droning noise is engraved in my brain! human nature Eh!!!

Carsy

Great news, thanks for the feed back , not everyone does as you say.

Pinching yourself & smiling will stop the drone!!