C180 Gearbox Noise ?? - Help !

[bradspau]

I have a manual 1998 C180 W202 Classic. When driving, I intermittently get a low pitch grating-type noise, that comes and goes, (sorry, it’s difficult to describe!) around the 2,000 and 3,000 rpm mark. I am assuming it is coming from the gearbox/clutch area. When I dip the clutch, the noise disappears. It does it in every gear, but is more noticeable when pulling away and in 1st and 2nd gear. It’s always done it…is this a ‘feature’. It doesn’t seem to be causing any problems and it isn’t particularly loud, but I am just intrigued to find out what it could be. Thanks in advance for your help.

 

[NormanB]

No experience of a manual MB - but.

Can you hear this noise with the engine in neutral can you invoke it by depressing the clutch - it could be the clutch thrust/release bearing (hopefully).

NormanB

 

[Brian WH]

I have a manual 1998 C180 W202 Classic. When driving, I intermittently get a low pitch grating-type noise, that comes and goes, (sorry, it’s difficult to describe!) around the 2,000 and 3,000 rpm mark. I am assuming it is coming from the gearbox/clutch area. When I dip the clutch, the noise disappears. It does it in every gear, but is more noticeable when pulling away and in 1st and 2nd gear. It’s always done it…is this a ‘feature’. It doesn’t seem to be causing any problems and it isn’t particularly loud, but I am just intrigued to find out what it could be. Thanks in advance for your help.

Sounds as if it could be the Clutch plates worn out mate.

Try pulling away with plenty of revs and slightly dip the clutch to see if you can get it to "slip", you will hear it, keeping the revs on. If it slips then it is worn, if it doesnt slip but disengages only, then it could be the bearing.

Hope this helps.

 

[Simon]

How many miles has it done?

I don't think it's typical, or a feature of the model as mine's nice and quiet @ 92000 miles.

My first thought was it might be the propshaft universal joint but you say it stops when you depress the cluch, so it's not that as the prop would keep turning anyway. I think the others are right - cluch / release bearing. These would not cost a fortune to have replaced.

Keep us posted.

 

[Dieselman]

I doubt it's the release or thrust bearings as it makes the noise when the clutch is engaged so neither the release or thrust bearings are in use. Both would be more of a problem when the clutch was disengaged.

Brian may be onto something as the rev band is when most torque is generated so slip will be greatest.
One thing bothers me though. if the clutch was bad enough to slip in first and second it wont drive the car in fifth, especially up hill.

Try this test.

Handbrake on firmly, gearbox in fourth, rev the engine and dump the clutch. good clutch = engine stalls sraight away, bad clutch = no stall or long slip.

One thought comes to mind. is the exhaust close to the body so causing harmonics or does it blow slightly?

 

[Alex Argent]

My money would be on the thrust release bearing. Although I have driven autos for a number of years, the symptoms sound the same as the problems I have experienced on previous manual models. The noise can be more or less apparent when the clutch is either engaged or released - depends on the nature of the bearing failure. Not exactly a 'big' job but fairly labour intensive (exBenzive!) as the gearbox obviously needs to be dropped down to get at it. If it's a job you feel comfortable doing yourself, it might be worth thinking about changing the clutch pressure plate and drive plate at the same time, especially if the car has covered a considerable mileage. Most modern clutches should be capable of 100k+ miles, but the release bearings can tend to wear out sooner, especially if one has the habit of 'riding' the clutch (i.e. foot resting hard on the clutch pedal between changes).
In saying all of that, it will be prudent to undertake the simple slipping tests mentioned in previous posts.
Hope that helps!
Regards,

 

[bradspau]

Thanks for all your suggestions. I will try the clutch test tonight and let you know the outcome. Car only has 55,000 miles on it, should the bearings be worn to that extent already?. Presumably the clutch test only test for a slipping clutch. If the test passess, I assume it could still be the bearings?? - Has anyone got an idea of the cost involved at a merc specialist NOT a stealership? Confident to do it myself though, but need to be absolutley sure its the bearings first. Dont want to do all that hard work for it to be the same after.

I get underneath at the weekend and check the exhaust mountings, etc, as suggested by Dieselman.

 

[Alex Argent]

QUOTE=bradspau........Confident to do it myself though, but need to be absolutley sure its the bearings first. Dont want to do all that hard work for it to be the same after.....QUOTE

....which is why it may be worth considering changing the entire clutch whilst you've got the gearbox off. 55,000m doesn't sound a lot, but it depends on how it has been driven (previous owner(s)?).

Can't comment on stealership prices, but would hazard a guess at approximately 3 hours labour, most of which would entail 2 pairs of hands = 6 hours @ say £55 p.h. = £330 plus parts + VAT.

If you're happy to have a go yourself, you could save a bit more by buying independently of the dealer. Check parts prices on:

www.gsfcarparts.com and/or www.eurocarparts.co.uk

Remember to add VAT. Also, there's usually a choice of OEM parts or third-party parts - your choice!

Regards,

Alex

 

[jimmy]

Depends on how it's been driven but a clutch should last more than 55K miles. A new clutch kit would be around £150 or so and fitting time is quoted at 3.8 hours.

Note I said clutch kit, if you are taking the engine or gearbox out you always put a whole new clutch kit including cover, plates and release bearing in even if it is found not to be faulty.