Supercharger Rattling

[littlebrooklyn]

It seems that our car has been rattling when idling for some time. Today my partner took it down to the stealership thinking it was just an idler pulley bearing, but apparently it's a clutch rattle from the supercharger.

We are taking the car in tomorrow for an assessment as they said it may need a new unit, but not sure if they just mean a whole new supercharger assembly or whether the clutch is a separate component that bolts onto the end of the supercharger itself...I have to say we didn't even know it had a clutch on that

The car has only done 25,000 miles, is this the kind of thing that goes wrong so soon? We have no idea at the moment whether it's covered under the warranty and just hope that it is.

 

[jimsinessex]

My 1999 CLK 230K had a kompressor clutch replaced at 62000 miles, the symptoms were a screeching noise rather than a rattle and the diagnosis by MB was the clutch bearing. The bad news was that the whole kompressor had to be replaced as the clutch unit was not available seperately, the even worse news was the car was out of warranty!
I asked for some goodwill and eventually MB offered 50% labour and parts, the whole job cost me about £600.
If your car is still within the warranty period it should definitely be covered in full.
I believe on the latest models the clutch has been eliminated, I can't understand why one is needed anyway.
Good luck

JIm

 

[zishan03]

Did the supercharger start to sound a little more high pitched by any chance?

Thanks

Zishan

 

[littlebrooklyn]

Well luckily the supercharger is covered by the warranty, so it goes in at the end of the month for a new one. We hadn't realised it had a clutch on it either. I don't think it made a more high pitched noise, just a rattle. In fact to be honest I can't even hear the rattle, but my partner used to be a Service Manager for another manufacturer and has always been really good at 'hearing' noises that a lot of other people don't even realise are there.

 

[philharve]

My C230K is a W202 of 2000 vintage. It has covered 97,000 miles without trouble. When you do get to hear the supercharger, such as when accelerating hard, it sounds like a vacuum cleaner, otherwise it should be virtually silent.

I can imagine that a well-worn supercharger would rattle due to worn rotor bearings but not until after a considerable mileage has been reached. A colleague, a chartered mechanic, informed me that the supercharger is capable of prodigious mileage and could last as long as the engine.

The clutch you mention is for engaging the supercharger. It is a magnetic design and has acquired a degree of notoriety for being a weak component. My C-class supercharger does not have a clutch, it was dropped from the design, and is engaged full time blowing air into the engine whenever it is running.

The supercharger is a simple design but precision engineered. The gap between the rotors is miniscule but over time they could make contact due to worn rotor bearings causing a rattle. The supercharger is a precision piece of kit and must be exchanged. You can't fit new bearings or a clutch without specialized equipment. Not a job for your average garage.

The precise nature of the supercharger explains why it is so expensive to replace.

The mileage you quote suggests the supercharger, or rather its clutch, is defective. Normally you would not expect clutch trouble with so few miles on the clock

REGARDS Phil

 

[mjtray]

When I was running a W202 C230K as a company car I had to have the supercharger replaced at 30,000 miles as the clutch was rattling badly.....sounded like a load of rusty bolts being shaken in a metal bucket!!

I had inherited the car from another employee who used to drive it hard and the service department at the garage mentioned that after driving at speed and then coming to a stop where you want to switch off the engine, you are recommended to let the car idle for a minute or so, so that the oil can cool down the bearings. If you don't you run the risk of the oil burning off the bearings, thus creating wear when you start the engine again.

Exactly the same principle should be applied to turbo's.

By the way I'm not implying that you drive your car hard....but if you do a lot of motorway miles, pull into service stations and just switch off, it could have an effect on the supercharger.

Thankfully yours is covered by warranty

 

[philharve]

Hi mjtray

The tip about letting a supercharger 'cool', just like a turbo, after a high speed run is new to me. I'll remember this. I don't do fast runs then suddenly switch off. Usually my road speed drops dramatically as I near my destination, e.g. cross country then town driving. I guess this gives plenty of time for the supercharger to cool before switching off. I suppose premature supercharger failure could result from the driving style you describe.

Does the supercharger share its lubrication with the engine, i.e. the same oil, and is it supplied under high pressure, i.e. does the supercharger have its own pump?

I've heard the clutch problem is usually caused by an electrical malfunction?

REGARDS Phil

 

[robbi-wan]

Exactly the same principle should be applied to turbo's.

Given that turbo's work in a different way, the turbo unit will have cooled sufficiently by the time the it has stopped spinning and you have parked.

rob

 

[littlebrooklyn]

Well we have only owned the car since May this year, so I'm pretty sure it's nothing to do with how we have been driving it, but I hear what you are saying