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Engine Whine at acceleration (w/ A/C)

9K views 4 replies 3 participants last post by  houseofdiesel 
#1 ·
Have any other forum member's R-classes experienced (suffered) engine whine --akin to a turbo spin or soft, high pitched jet sounds upon acceleration, especially at low RPMs starting from 10 MPH or less, such as in stop-and-go traffic? I have noted that turning off the A/C eliminates the whine and restarting it brings it back again.

After searching the various forums, I tracked down the following service bulletin re: A/C compressor drive belt noise (defective pulley) that may explain the problem; please see the attached downloaded from Mercedes-Benz Forum.

Has anyone had this repaired and if so did it cure the symptom mentioned above? Thanks in advance for your help.
 

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#2 ·
If the problem goes away when you turn the A/C then it's likely the problem...I notice some noise when the A/C is turned on and off in my R500 - but only at idle. While you are fixing this have the power steering pump checked as the R500 is famous for power steering pump failure (first whining noise, then stiffness in the steering wheel).
 
#3 ·
You were exactly right about the steering noise. Dealer replaced the steering pump and reservoir, and the steering groan is gone. Two much more minor sounds remain: (1) occasional hum (whine) at acceleration with the A/C on and (2) creaking (more of a feeling than a sound) when turning left at low RPMs.

I agree that the "necessary condition" of A/C being on strongly suggests a bad bearing in the A/C compressor or related component. I only wish it would occur all the time. I think I'll wait until it is continual nuisance or until I know the circumstances when it arises so at least I can replicate.

As for the second, I also need to continue to investigate. It seems to occur about half of the time when I make a hard left turn accelerating at low RPMs. It could be the rack and pinion that you suggested previously. Other postings suggest a bad left VC joint, which seems likely.

Thanks again,

Tom.
 
#4 ·
CV Joint Diagnosis

Why I think it's the CV Joint. The following are the CV Joint diagnosis that I found:

1 Hearing clicking noises. A sure sign that your CV joints are in distress is hearing a pop or click when turning. To make sure the CV joint is the problem, put your car in reverse, turn the steering wheel all the way to one side and back up. If the pop or click increases, you need a new CV joint.

2 Hearing a clunk when speeding up or slowing down. When you increase or decrease your car's speed and are met with a clunk, then this could be a symptom of worn CV joints. To check, drive your car in reverse, then switch between speeding up and slowing down. If the clunk gets louder, it is a sign that your CV joint has gone bad.

3 Hearing a humming noise. If while you are driving, you notice a humming noise or something that sounds like a growl, the CV joint may be bad. This is because there is not enough oil or lubrication around the joints due to a damaged wheel bearing.

4 Feel a shuddering when speeding up. If there is a shuddering or a vibration when the car is going faster, it could be a sign of a damaged inboard plunge CV joint. Still, it could also be a sign of axle problems or faulty motor mounts. It is best to find out for sure before proceeding with any repair.
 
#5 ·
R320 CDI tuning/remap info chips?

I want to have earlier power in my 2008 r320, meaning quicker throttle response and acceleration off the line. I have lots of experience with diesels, and a reflash on my other cars really helped with these issues. I am long out of warranty. Anyone have some helpful advice/info/suppliers to recommend? I don't care to delete any emmissions controls, I find the fuel economy just fine and like having clean chrome tailpipes unless you sell me otherwise, but we are getting readiness code emission testing here in Ontario so it has to work without faults. I find it is really hard to build boost in the r class and keep it in the same gear, it always wants to downshift so it is impossible to use more the 70% of the engine at low rpm (what is the point of 400lb/ft of torque at 1600rpm if you cannot use it?). i just roll on the throttle in my other automatic diesels and enjoy the torque!
 
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