CLS55 Engine Rattle

[BeansMeansCLS]

Had my CLS55 fitted with a 77mm pulley and map, car made really good power both stock and after the pulley upgrade.

Recently however I've noticed a rattling sound coming from the engine bay on idle - on closer inspection it seems to be coming from the top of the engine/rear of the supercharger close by to the throttle body.

As far as I'm aware it wasn't making this sound before, any ideas?

The rattling has now got me worried it could be something major!

 

[AMGeed]

These aren't the quietest engines on tickover, but a rattling sound isn't normal.

In your position I'd take the car to my indy to have it checked out.

 

[BeansMeansCLS]

Will take the supercharger belt off tonight to rule it out, if it does appear to be the charger, what are my best options?

Is it worth sending to someone to refurbish or just bolting a second hand one on? I've heard the internal bearings are a bit difficult to change

 

[BeansMeansCLS]

Update: with the belt off (SC disengaged) I don't hear any rattle. Spinning the charger manually with the belt off, no rattle.

Put a stethoscope on the surge tanks and I can hear the rattle, it sounds like its coming from the rear of the surge tanks. Have uploaded a video.

 

[BeansMeansCLS]

Video (sound becomes clearer at 8 second mark):

20190128 195902

 

[andy27168]

Hi,
I have had very similar issues with my charger on my CLS once was a faulty charger pulley (84mm) the rivets had become loose. Then latterly which seems to be the same noise you are having I never got to the bottom of it I weighed up my options talking to companies about rebuilding it which was around £1500 IIRC.
After much deliberation I decided on a second hand unit which I found on Gumtree less than 10 miles from me complete with throttle bodies, surge tanks and front pulley from an S55K for £550.
Speaking to PCS and looking at other forums etc it appears it is almost unheard of for one of these chargers to fail especially on a car with less than 100k miles (about 90k miles).
The only issue I have had which is more of a niggle than anything is the build plate for the engine which is on the charger I want to swap them over but cannot think of any way of getting them off of the charger.

 

[eight]

Does sound like bearings - if it doesn't do it with the charger belt off, you've found it
I changed the oil in mine - might be worth a go?

 

[BeansMeansCLS]

Hi,
I have had very similar issues with my charger on my CLS once was a faulty charger pulley (84mm) the rivets had become loose. Then latterly which seems to be the same noise you are having I never got to the bottom of it I weighed up my options talking to companies about rebuilding it which was around £1500 IIRC.
After much deliberation I decided on a second hand unit which I found on Gumtree less than 10 miles from me complete with throttle bodies, surge tanks and front pulley from an S55K for £550.
Speaking to PCS and looking at other forums etc it appears it is almost unheard of for one of these chargers to fail especially on a car with less than 100k miles (about 90k miles).
The only issue I have had which is more of a niggle than anything is the build plate for the engine which is on the charger I want to swap them over but cannot think of any way of getting them off of the charger.

I'm thinking the same, a swap with a second hand unit would be the most cost effective option.

Going to investigate a bit more tonight. Someone has suggested using a drill to turn the supercharger (whilst the engine is off) by screwing a bolt into the front breather port (in the centre of the pulley) and listening for noise.

 

[andy27168]

Hi,
I thought about doing similar, wasn't really worth it, the charger was noisy, to get rid of the noise was either a rebuild or a second hand one, and as I said I went with a second hand one.
Good luck with whatever you find/decide to do.

 

[Gbrowncls55]

Unlikely to be the supercharger itself as at idle its not running (clutched taabout 1800 rpm I think). But yes of course it could be either of the mail puuleys or an idler pulley. removing the belt will get you a step closer.

 

[moodi]

Unlikely to be the supercharger itself as at idle its not running (clutched taabout 1800 rpm I think). But yes of course it could be either of the mail puuleys or an idler pulley. removing the belt will get you a step closer.

He did remove the belt and noise went away

 

[andy27168]

Gbrowncls55 does have a very good point regarding the supercharger not running at idle.
Do check that you can stop the charger turning with the engine running do this when the engine is both cold and also when hot, if you cant stop the charger from turning on idle then the charger belt pulley hasn't been correctly shimmed.

 

[BeansMeansCLS]

Not necessarily true,the magnet is definitely engaging at idle, I can hear the magnet disengaging once I switch the engine off.

With the belt off, the pulley was only free to rotate when the engine was off and magnet had disengaged, if you look closely you can physically see (and hear) the magnet disengaging from the pulley. The sound appears to be originating from the drivers side charge tank.

 

[Gbrowncls55]

Pulley should be disengaged from charger at idle and up to 1800 rpm or thereabouts. If yours is running there would appear to be a s/c clutch fault. Whatever sound the supercharger makes if running at idle could perhaps be heard from the area you suggest. I've never heard it but then mine does not run at idle.

 

[alexanderfoti]

The superchargers turn at idle and low RPM due to air moving through the charger. If you run the car with the belt removed, the charger still spins, but can be stopped.

However, if your magnet is engaging at idle, then you have a fault, and you are probably hearing the chattering in SC gears.

I would disconnect the electrical connector to the magnet and see if the noise goes away.

 

[BeansMeansCLS]

Are we 100% sure that the magnet should never engage at idol?

Will carry out more investigation tomorrow....let's hope it doesn't snow!

 

[alexanderfoti]

1000%

Who fitted the pulley? If it isn't shimmed correctly it will engage at idle when it shouldnt, even without the clutch engaged.

The clutch is switched ground so if there is a wiring fault or a shirt to ground, it will engage.

 

[BeansMeansCLS]

It was fitted by MSL. There seems to be a correct gap between the pulley and clutch, it spins freely and doesn't contact - I've heard some people run with no shims at all.

 

[BeansMeansCLS]

1000%

Who fitted the pulley? If it isn't shimmed correctly it will engage at idle when it shouldnt, even without the clutch engaged.

The clutch is switched ground so if there is a wiring fault or a shirt to ground, it will engage.

Regardless of whether the pulley is shimmed correctly or not, the magnet shouldn't be on at idle? - Magnet ON = pulley engaged, Magnet OFF = pulley disengaged.

I can't see a scenario where incorrect shimming would cause engagement at idle unless the surfaces between the clutch and pulley are directly touching which they're not.

UPDATE:

Disconnected the electrical connector for the magnet and I can stop the supercharger spinning at idle, there's no rubbing and good clearance between the clutch surface and pulley - the magnet is definitely engaged at idle.

With the supercharger not spinning...there's no noise The rattling seems to be originating from the back of the supercharger towards the throttle body.

I'm going to change the supercharger oil to see if that makes any difference then report back.

The constant engagement of the magnetic is another issue.....

 

[moodi]

Just checked - my magnet is also on from start (super cold start if that makes any difference) and couldn't stop it by hand. No issues with rattling.