michail71

This is related to my thread on a whiney sound that my car has. https://mbworld.org/forums/c-class-w...r-c-whine.html

I purchased a mechanic's stethoscope and pinpointed where I think the low speed whine is coming from. Basically from 1,500-2,700 RPMs the car has an unpleasant high pitch whine to it. The dealer has so far replaced the tensioner and the guide pully without making any real difference that I can tell.

I checked the various components on the serpentine belt and for the most part they just hummed along. Then when I got to the power steering pump I heard the screech in the attached recording. I verified the fluid levels are good.

It took 3 people but I had someone hold the scope ear piece to the phone microphone. Someone else was revving the engine between 1,500-2,000 RPM.

Can anyone confirm if this sounds normal or have ears trained to tell what is going on with this.

Carsy

Hello Michail ,

Were you turning the wheel when recording the sound ?.That would explain the changes in tone.

It would be interesting if you had gone all the way to full lock to hear the relief valve lift ?.

Some parts of the clip sound quite metallic in nature .

I have just stopped being lazy & gone out & started my car & put the stethoscope on. My wife turned the wheel to full lock & back . I have no such metallic noise, just a quiet hiss of throttling fluid through the pump with a final hiss at full lock. Definitely not the variation in tone you have.

I would suggest a problem with yours but hesitate because we do have different stethoscopes & the sound recording may reproduce sound differently.

Surely your workshop could compare two cars with their stethoscope?

Good luck.

michail71

Thank you! The wheel was not being moved at all. It was just the engine being revved up and down. I suspect it's the bearings.

When I put the probe on other pars of the car I would hear hums, ticking and other such sounds but they seemed much more quiet and pleasant in comparison. To put in in perspective the fans sounded louder than what I could hear on the other components. This was at lease 4x as loud as anything else on the car. It sounded much worse with my ears than the recording sounds. It really screams. At one point with my ears I thought I heard what sounded like metallic debris being ground up.

The pitch of the note is about spot on with what I heard driving, which is what is making me think this is the problem.

Thank you for taking the time to listen to your car and compare! I've already had the dealer replace two pulleys and was starting to think the problem was just me. But I shouldn't have to work so hard at getting the dealerships to fix issues I was able to find with a $10 tool from the parts store.

michail71

The funny thing is the dealer told me today they couldn't make out the audio file I had sent them because it was "too garbled". I forgot to mention that it's not garbled and that's exactly what it sounded like, lol.

But they are going to scope it while it's in getting the timing chain fixed and compare it to another car.