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Old 05-01-2002, 07:50 AM
Registered User
Join Date: Dec 2001
Location: LaPorte, IN
Posts: 400
Unhappy Groaning engine sound

Sunday night while leaving a stop sign, there was a pop, and from then on I have had a constant groan from the front of the engine bay. Only present with the engine running and has a rhythmic quality that increases with speed. Seems to be coming from the belt area, but I am suspecting hypraulic pump because the ride seems different than it did, harder.

No visible leaks from the rear shocks, accumulators or lelevling switch. Fluid level is fine and fluid is pumping through with no air visible. The whole time we've had this car there have been popping noises-3 or 4, in the first 10 minutes or so after shutting off from a drive. I figured it was the rear suspension settling. I've not noticed it since Sunday though.

If the accumulators have gone south, could it cause the pump to strain and groan? If it is the pump, is it likely gone? Can I remove the fuse for the hydraulic pump, start the car and see if the noise is gone? Thanks.
Earl McLain
'02 C230 Kompressor
'89 560 SEL "Frau BlueCar" (retired April 2004)
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Old 05-01-2002, 07:30 PM
Posts: n/a
I had a groaning noise in the front of my car and it turned out to be the pully and tensioner shock for the serpentine belt that went bad.
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Old 05-01-2002, 07:45 PM
MikeTangas's Avatar
Senior Member
Join Date: Apr 2000
Location: So. Cal
Posts: 4,430

I had a strange moan from the 560 too, but it went away when I changed the accmulators. I suspect the moan had something to do with the "foamy" fluid when I bled the system down. With the rear of the car up on ramps, place a piece of clear tubing on the bleeder screw (to see the condition of the fluid and to allow for proper disposal) at the leveling valve, then loosen the screw just a tad (11mm I think). Caution, the rear of the car will settle as you bleed off suspension fluid. If the fluid comes out foamy, then the accumulators are probably shot.

You can't pull a fuse to disable the pump, it is bolted directly to the front of the block and is driven internally.

Try the bleed test and report back.
Mike Tangas
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72

'02 CLK320 Cabriolet - wifey's mid-life crisis

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Old 05-02-2002, 07:32 AM
Registered User
Join Date: Dec 2001
Location: LaPorte, IN
Posts: 400

I have accumulators on the way, figure it can't hurt anyway. When I pulled the filter out of the reservior I accidently spilled an ounce or so of fluid, now the groan is quieter. Glad to hear of your experience, gives me hope. It will be Saturday or Monday before I get this done, but I may get to the bleed screw tonight. BTW, I couldn't turn the nut on the link at the levelling valve Tuesday night, and the bolt has just a round head, like a carriage bolt. Any trick to removing that other than some penetrating oil?
Earl McLain
'02 C230 Kompressor
'89 560 SEL "Frau BlueCar" (retired April 2004)
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