W245 - an irregular rattle/knock when cold from the lower front left

[chris10895]

I have a 2011 B Class petrol 1.7 with 59K on it which (more often than not but not always) rattles from somewhere low at the front … I'd say somewhere around the clutch housing area. Depressing/engaging the clutch or selecting a gear makes no difference.

It's a heavier sound than such as a slack timing chain (which is at the other end and is fine)
Once run for several miles so that it is well and truly hot, the noise disappears but whilst evident it is concerning. Clutch? Splines? Clutch plate shock absorber springs? Transmission (which was rebuilt after 30K due to worn bearings!!)? I can't think of anything that is driven from the left hand side of the engine except the clutch and transmission.

Anyone experienced the same and know if it's something to be concerned about? I can't imagine that it came out of the factory like that.

I might be able to record the sound and upload it as an audio file.

And, in case you wonder, neither of two dealers can or will offer a suggestion as to what it might be … but then they didn't diagnose that my cam-chain hydraulic tensioner was losing pressure … I worked that out myself and asked them to renew it. Timing chain noise disappeared.

 

[Rodg]

Can't help Chris but I found your problem while looking for a solution to exactly the same problem - except I have a 2001 auto S3200 It doesn't sound that loud in the care but today when I opened the window I realised just how loud it is. It goes if I brake or if I drive for 20 minutes. Hopefully we both find some good advice.

 

[chris10895]

Can't help Chris but I found your problem while looking for a solution to exactly the same problem - except I have a 2001 auto S3200 It doesn't sound that loud in the care but today when I opened the window I realised just how loud it is. It goes if I brake or if I drive for 20 minutes. Hopefully we both find some good advice.

The noise isn't evident immediately on start-up but after a few minutes, in it comes … irregular and quite prominent … and hollow sounding as if in a box, such as a large casing like there clutch housing. Then, after a drive or even 10 minutes idling, it has calmed down and become quieter and regular. Finally, after a run it virtually disappears.

I lifted the bonnet and the source then seemed to be more central, so it could be 'travelling' through various components. I have considered the gearbox and its oil … levels too high or too low or wrong grade … but since it is not stopped by depressing the clutch, at which point all the gearbox components should be stationary, that seems unlikely.

In some ways I regret buying this car. I put a total of 250,000 miles commuting on a pair of W168 A Classes with few problems … broken rear springs and a new set of belt pulleys, on the early one (plus the inevitable renewal of brake discs) and hoped for the same reliability. This B Class has had a rebuilt gear box (after 30K), new drive shafts, lower ball joint, front wheel bearings (twice on one side), starter motor, front anti roll bar with bushes plus drop links, rear bushes, and new engine mounts. New rear dampers are about to be fitted and there is a persistent but intermittent squeal from the drive belt or its pulleys which may need attention. Various items of plastic trim have distorted or cracked with age. All this on a car that has been treated well and with a full MB service record. Not inspiring! Pity because it has a number of unique and desirable features that I look for in a car.

The car is going to the local Mercedes dealer this week and they have been asked to investigate the noises. I'll keep you posted.

 

[mioba]

I would be inclined to find a good mercedes indy to diagnose and fix the issue. Any dealer as you mentioned will throw money at the car. Paying through the nose is going to make you fall out of love with the car in no time at all.

 

[alexanderfoti]

Don't rule out things on the aux drive (AC compressor, altnerator etc) Is it possible to video the sound?

 

[chris10895]

I'll try and record the noise tomorrow morning from cold. I have been to both the main franchised dealer and the independent one that I bought the car from a couple of years ago. The latter haven't been able to offer any sort of explanation … they specialised mainly in the older 'real' Mercedes and I suspect that they rarely saw one of the 168/169/245 series. In any event the dealership has been sold and the new owners have set their stall up as a classic car dealer with less emphasis on the Mercedes marque.

I take the point about considering the auxiliary components … noise can travel through the engine bay and there are already question marks over the state of the drive belt and pulleys with their tendency to squeal, though not on every journey.

Watch this space.

Incidentally, off topic for this section but connected with my early disenchantment with the car … the handling was appalling … it would lurch viciously off course when encountering road irregularities, so much so that I thought of getting rid. Then I looked at the tyres … three were Michelins (Energy Savers) and the F/O/S was a Firestone, put on by a dealer when it was sold to the trade. A full set of Michelin Cross Climates transformed it. The moral is … don't mix makes of tyre on the front.

After the current issue is resolved (I hope) perhaps I'll post a list of 'gotcha's' for protective buyers and current owns of this model at a suitable place in the forum. It might save some tears and expense for someone else.

 

[grober]

Dual mass flywheel? As the springs weaken the front and back plate can knock against each other. As the assembly warms up with the use of the clutch and engine warming up the slack might be taken up quietening things down??

 

[chris10895]

Petrol engine. I believe that DMFs only apply to the diesels … although I stand to be corrected.

 

[chris10895]

Apologies for the delay in posting an update. The car went up on a lift last week to sort out the suspension and to have a closer listen. The finger is being pointed very much at the pulleys of the serpentine belt ... the squealing sound has become a regular feature and it seems to relate to the knocking/rattling which does reduce after a while. Hopefully the pulley set (it comes as a 'cassette') can be replaced in the next couple of weeks and will either prove or disprove the diagnosis.

I'll post the result once it's done.

 

[grober]

If your alternator has an overrun clutch drive pulley you should seriously consider changing that at the same time? Many poly v belt tensioner / pulley problems are as a result of overrun pulley mechanism failure.

 

[LostKiwi]

Belt tensioner pulleys can knock when worn.

 

[chris10895]

Interesting replies and thank you. I do wonder how it is that I can go to both a main franchised dealer and an independent Mercedes garage and neither has yet come up with these ideas ... save that the technician at the main dealer has pointed out grease contamination of the area, possibly from a previously split CV rubber boot, and some discolouration of the tensioner pulley metal body. No mention of alternator overrun clutches. I'll look into that aspect ... it's not very clear if I have one fitted although I see that the pulley on the car is hollow on its outer face whereas all images of overrun clutch pulleys on the internet show the pulley face flush with the rim (presumably because there is the clutch mechanism inside it).

 

[chris10895]

Apologies for the long silence … the issue now seems to be resolved.

After replacement of the pulley pack/tensioner/poly-v-belt (the noise continued), running of the engine with the poly-v-belt removed (the noise stopped), replacement of the water pump (the next and cheapest option suspected by the technician before considering the AC compressor or alternator) (the noise returned) … it was the crankshaft pulley!

Apparently there is a rubber centre section which acts as a vibration damper … in this case it was reportedly hanging together by only a small part of the rubber structure.

So, going back to my original post … although the noise seemed to come from the clutch/gearbox area, the noise obviously did travel through the engine. Why it disappeared when things had warmed up, I have no idea.

Tomorrow morning will be the acid test after the engine has cooled overnight. I now need to anaesthetise my wallet … fortunately the dealer did not charge for the water pump as it had been on their recommendation but proved to be wrong, but the cost has still been painful.

Thanks for all the suggestions and advice.

 

[Wighty]

Apologies for the long silence … the issue now seems to be resolved.

After replacement of the pulley pack/tensioner/poly-v-belt (the noise continued), running of the engine with the poly-v-belt removed (the noise stopped), replacement of the water pump (the next and cheapest option suspected by the technician before considering the AC compressor or alternator) (the noise returned) … it was the crankshaft pulley!

Apparently there is a rubber centre section which acts as a vibration damper … in this case it was reportedly hanging together by only a small part of the rubber structure.

So, going back to my original post … although the noise seemed to come from the clutch/gearbox area, the noise obviously did travel through the engine. Why it disappeared when things had warmed up, I have no idea.

Tomorrow morning will be the acid test after the engine has cooled overnight. I now need to anaesthetise my wallet … fortunately the dealer did not charge for the water pump as it had been on their recommendation but proved to be wrong, but the cost has still been painful.

Thanks for all the suggestions and advice.

That's good of the dealer not charging for the water pump . Glad it's finally sorted , sounds like it was caught just in time