Hi, couldn’t readily find any other thread that described this issue (including the “noises” sticky) so posting here.

Background: 2002 C230K coupe fastback/hatchback with ~150k miles, only owner & bought new ~23 years ago, I dutifully do my Service A + B & whatever other maintenance/repairs are required.

Issue: experiencing severe vibration noise & shaking ONLY when turned all the way to the locks. Very noticeable when I exit my garage as I have to make a 90° turn. The car literally sounds & feels like it’s going to shake itself apart!

Troubleshooting: Took it to a local mechanic & he claimed maybe it’s the power steering pump but then later insisted it’s the supercharger (which I disagreed with & is expensive to replace too). He then replaced one of the idler/tension pulleys (even though I didn’t think anything was wrong with it). In the end nothing was really solved.

I’ve attached an MP3 of the sound in the hopes someone may have an idea what the cause & solution could be!

Note, in the recording (recorded from the driver’s seat) I turn the steering wheel all the way to the right as I exit the garage & the vibration/shaking occurs @ +~3s. I then move forward, break, then turn the wheel all the way to the left & the same vibration/shaking occurs again @ +~19s.

Any help appreciated!

PS: I have limited help & tools but am willing to do whatever to fix the issue. Also, FWIW, some stored scanner codes:

• TCM - Transmission Control Module: 2

1. P2600 The Voltage Supply Of Circuit 87 Has Undervoltage: Stored
2. P2315 One Or More Messages From Control Unit A1 (Instrument Cluster) Are Not Available On The CAN Bus: Stored

Thanks!

 

Your mechanic is a genius. A Supercharge issue? Really? Did he also check the fragrance flacon in the glove box?

But seriously...
Rear diff and half shafts?
Suspension components all good?
Not much else could cause noise / shaking only at extreme turns.

Unless the fart filter in the seat needs replacing?

 

If I were in your shoes I'd remove the serpentine belt and check each pulley. The one that usually has a problem is the sprag (1 way) pulley attached to the alternator which can seize up, but it makes a different noise.

Actually I think the M111 (that's the engine you have) supercharger is known to have problems for some people on this forum. I have a different engine so can't comment. Hopefully someone else can chime in. With that said, I'm going to guess that this isn't the problem you're dealing with.

 

Can you tell if the noise is from the belt slipping on one of the pulleys for a component that is dragging (i.e. the PS pump)? Or is the noise coming from the component itself. Can you have someone turn the wheel while you check?

For PS pump I vaguely remember another thread from a long time ago about people blowing out their pumps doing donuts with their cars, wheel turned to lock and high rpms. The release mechanism in the pump doesn't handle both at the same time very well. Could be your pump was subjected to similar strains at times so the relief mechanism is now damaged.

 

Thanks for all the replies. I think all pulleys have been replaced now (to my mechanic’s credit there is a pulley on the supercharger but pulley sound issues typically are constant & not something that only occurs during startup AND (even weirder) ONLY when the car FIRST starts up for the day (could it have something to do with the power steering fluid being cold/non-expanded at the beginning of the day? I notice the reservoir level seems to drastically change depending on when I check it). Where is the power steering pump when standing in front of the hood?)

After driving 45 mins in city traffic to get to the mechanic’s shop, I now can’t reproduce the issue… argh!

Re. the below:

> Rear diff and half shafts?
> Suspension components all good?
> Not much else could cause noise / shaking only at extreme turns.

Probably? I don’t really hear any other creaking except rotor breaks, but will ask to check when I get back on the lift, but again would issues like that only happen on first start of the day??

Never did donuts with this car or really push the car that hard these days now that I work from home (at most only 1-2 miles a weekend to restaurants or grocery stores)

Truly stumped as to the cause!

PS: did the sound in the MP3 provide any clues? FWIW, the sound does seem louder nearer the supercharger area.

 

With the problem only showing up when steering wheel turned to full lock, the likely cause would be the power steering pump.

This vibration sounds wildly violent, so I expect this problem to be easily spotted. Find a helper to watch your engine bay while the problem is recreated, or try to record a video.

 

There is a TSB that the fluid level must be higher than printed on the reservoir, so put it when cold between max cold and min hot level.

Questions (to get an idea if the engine is ok):
Does it occurs only when the engine is cold? ->cold engine runs on fixed AFR and has high load during SAI
If yes, during Secondary air injection cycle or after? -> during SAI the belts have a higher load than on warm engine
Are both belt tensioners ok? -> belt slip at supercharger, common problem
Is the coolant sensor full of oil? -> wrong AFR on cold engine

It could be belt slip at the supercharger tensioner (25% change)

 

@112233 Issue ONLY happens once at FIRST startup of the day (so engine would be cold presumably). After that, I am unable to reproduce it (maybe I could if I left the car off for 12 hours again but I haven’t honed in on the exact duration required)

If the issue is related to loose belts, how could I visually tell?

Re. the coolant sensor: where is that located? Is it inside the reservoir?

 

@smgak , can I turn the steering wheel to the stops when off so I can “prime” the issue? Although thinking about it now, the wheel wants to “snap back” by ~30° if I turn it all the way to the stops, so it might be hard to rig it there.

Also, is there such thing as turning _too much_? Like are you allowed to turn all the way to the stops? ie: is that why it snaps back?

 

Another data point: FWIW, the mechanic claimed that the issue doesn’t occur if the belts are all removed (which would imply an accessory)… but unfortunately I wasn’t there to witness it … & I don’t know if he/his assistant turned the wheel all the way when they started the car.

 

@jkowtko , @slammer111 , how would I be able to tell if the belt is slipping? I think 2 of the 3 tensioner pulleys have all been newly replaced (#7,8 for “belt II” on p374 of the manual)

2002 MB C230K Coupe Manual, p274 Poly Belts


[edit: ok, just checked with Gemini on belt slippage symptoms & all the things it mentioned don’t seem to be an issue, ie: squealing, accessories not working as effectively, CEL, etc. Also, I think my mechanic installed a new belt a few months ago]

 

Ok! I think I found the culprit!
(made myself a DIY automotive stethoscope & carefully started poking things after a 2nd person started the car & turned the steering to the stops)

Seems to be loudest & originating from the (Bosch) throttle body assembly (see attached pic) which is mounted near part #20 & atop the front of the A111-098-037 intake connection (top L side of part labeled #17 in 2nd pic)


Bosch throttle body (Bosch part #0-280-750-045)

Intake connection (MB part #A111-098-1037)

My question: Is this really possible? I’m surprised a simple part with just a flap could cause so much vibration + noise & only when turning to the stops?

 

Good work. It might not be fastened properly.

 

The coolant sensor is under the front cover of the engine right below the leaking camshaft solenoid. Just take off the connector and look into it (you have a M111, right?)

Belt slip, you see lots of black rubber dust around the charger pulley. Otherwise it is hard to see. At the other belt you feel vibrations at the tiny dampener. I'm on my 3rd set of tensioners at the supercharger so far.

If it is gone at a warm engine, I would rule out the power steering pump with over 50%.

 

@smgak , it seems attached pretty tightly. If it were loose, wouldn’t it rattle all the time VS only at 1st startup?

@112233 , yes, it’s an M111 I believe.

Q1: I’m looking up replacement parts for this Bosch throttle body (part # 0 280 750 467 = MB part # A1110980109) & I am finding cheap Chinese versions for ~$100 (that I can get via Amazon by Sat Aug 30- perfect for me to repair over the long weekend) VS a replacement Bosch that is ~$300 (arrives after Labor Day weekend) VS a used Bosch for ~$29 (arrives Sat Aug 30~ Sat Sep 6). Which would you go with? Is this a safety critical part where the complete failure of it would be catastrophic at speed?

Q2: What tools + drive sizes do I need to replace this?

Q3: Do you need to do any ECU reprogramming if this is swapped?

Thanks!

 

Wait, this is the recirculation flap, that humming noise is normal, because it is an PWM motor inside.

During cold start the engine is going in secondary air injection mode. In this mode the recirculation flap is fully closed (humming noise) and the charger makes full pressure, therefore the high load on the belt. This mode is around 45 s long.
You can reset this flap very simple. Turn on ignition, wait 15 s, turn off, wait 5 s, ignition on, wait 45 s. Than you hear the flap moving, after that ignition off again 5 s.

If you want to remove the flap, you need E11 or 12 nuts, remove the silencer on top of the charger. Very easy work, there is some hose below it, otherwise you see everything that needs to be removed.

While youre in there, it is a good idea to clean the silencer inside from all the oil, there is an oil seperator inside, and regarding the flap, remove the plastic cover, and take out the motor (2 torx screws) and clean all inside. oil the bearings from the motor.

 

@112233 , “recirculation flap”? Surely this intense vibration from it couldn’t be “normal” when turned to the stops.

What do you mean by “reset”?

Also, what does the silencer look like? is this what you are calling the “throttle body assembly “? & where is it in the exploded diagram?

PS: I think within 45s the noise & vibration goes away anyway?

Thanks!

 

With reset, the flap learns the 0 and 90 degree position. Switch on the ignition, go in front of your car and listen. If you open the air filter housing, you can watch the flap.

The silencer ist the black intake connection part between air filter and charger inlet. Not on your schematic image

 

Ok, I did some research on this SAI & see various videos about what you’re talking about now but all those show a 2nd throttle body assembly in the back of the engine bay near the driver side, where the sound doesn’t appear to be originating from.

The sound is originating from the throttle body assembly in the front of the engine bay on the passenger side. I did find but the narrator says there would be other performance & codes, which I don’t. My question: is this front throttle body assembly only used for this SAI phase?

Thanks!

 

No, it is used to control the boost on normal operation. I add a video where you can see a dirty flap which can produce the P0410 error, compared to a cleaned flap.
Compared the the TB at the manifold it is much more noisy because it has to work against the spring which opens it up. The TB spring opens ist only a few degree not 90 like the recirc flap.
You will have to clean it on some day, it will fail. You can do a search P0410 in the net and can read all day long.

 

Thanks, but I’m not getting a P0410 code?

Regardless, I ordered a replacement part (arrives Saturday) & will try opening it up + working on the car / hopefully recording it this weekend.

 

I am finding variations of the Bosche throttle body assembly part #s (last 3 digits differ) but all have the same MB part # (A1110980109). Are these all the same & compatible with each other? (asking because some of these other variants only list it for the newer 2093+ 1.8L engine, were the hose diameters the same?)

Danken schon!

 

That is more for preemptive maintenance and that you get an idea how a dirty flap behaves.

Here you can put in your VIN and look what part number you have to buy

https://mb-teilekatalog.info

PS: Regarding to this video, don't spray anything into the check valve, it ends into the cylinder head. Get a crow foot and remove the valve for cleaning (or replace it).

 

So I have some good news & bad news, I replaced the throttle body assembly & it seemed to resolve the noise, vibration & shaking but only for 1-3 car starts before returning I don’t get it, why would it only temporarily fix the issue? Is the source really the supercharger as my mechanic was saying? (again, when I used the stethoscope prior to replacement, the noise was greatest from the throttle body assembly VS the supercharger).

Very disappointed as I spent 5 hours replacing the part… sigh

 

Any thoughts @112233 ? About to pull the trigger to buy a used supercharger (with good bearings & rotors supposedly) so I can install it over the weekend.

Thanks!