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whining noise - HELP!

8K views 15 replies 6 participants last post by  drbranko 
#1 ·
Hello all,

My SLK sat for about 3 weeks while I was in Europe. I got back exactly one week ago and started my baby with this strange grinding sound!? Ok... the grinding sound did not appear again and according to this forum it's kinda normal if car sits for a while...

BUT....

Yesterday I noted the whining sound, most audible around 40 mph, getting pronounced both during acceleration and slowdown. It sounds like a mosquito and its location is hard to pinpoint. It's either left front of the engine or left rear of the car.

So today I popped the hood and noticed a lot of cold water condensation around this cilinder shape (with a hose running toward the upper red engine cover) part located over the left front wheel compartment!??? Is this related? Yes it did rain this morning but the rest of the engine compartment was dry!?

Please help! Is this noise pointing out to a major failiure? I can't hear it while idling or at higher speeds? Your input is very much appreciated!
 
#2 ·
Sometimes if you get rid of your wife the whining stops. Is it gear noise? Try putting it in neutral and coast and see if it goes away, if it does then it's likely coming from the rear end. Check for leaks. I test drove a 99 SLK when I was shopping and it had a big rear end leak and it made noises that told me to avoid this car.
 
#3 ·
Well

Whineing noise under acc and decel,
1. Supercharger
2. Idler bearing
3. Aircon pump
4. Vacumn leak
5. Water pump
6. Drive belt
7. Pinion bearing
8. heat shield touching

???

Please have anothe rlisten with window open...

Bazzle
 
#5 ·
please look at this

Ok guys... appreciate your humor... but this is not funny at all...

The noise is still present best around 40 mph including coasting in neutral (manual 5 speed) bot accelerating and slowing down. It appears that the noise cannot be heard below 40 mph or above 45 mph....

It is most likely comming from the front left area of the engine.

Popped the hood again and there is lots of cool water condensation at the same place....

Obviously I have to stop by my dealership, but I would still like to be informed about what's going on. Any idea on the possible problem and/or what is this going to cost me?

Here's the photo:
 

Attachments

#6 ·
That looks like the aircon modulator. Condensation is normal as the gas inside is cold and the air outside has moisture in it.

Have you tried with aircon off the check that as a source?
It really is hard to diagnose noise over the net, sorry.

Bazzle
 
#9 ·
Ok, I test drove my SLK again trying AC on and off. The whining sound can be heard both with AC on and off. However it appears that the car has to warm up before the noise appears. During first few minutes I could not hear anything around 40-45 mph.
Any ideas???
 
#10 ·
And so it goes on.... today driving from work I lowered my windows... and oh boy... I could hear it more clearly as it was louder... could be comming from the rear end but I'm not 100% sure. What makes it a mistery is why it appears between 40-45 mph?
 
#11 ·
drbranko said:
And so it goes on.... today driving from work I lowered my windows... and oh boy... I could hear it more clearly as it was louder... could be comming from the rear end but I'm not 100% sure. What makes it a mistery is why it appears between 40-45 mph?
Does it change when you
a. brake (hold gently whilst accel)
b. pull Hand brake on slightly
c. swerve (safely)
d. are your tyre pressures OK

Bazzle
 
#12 ·
Well, maybe this is obvious... but have you tested it at a standstill in neutral? If you can, this should completely rule out the drivetrain all the way up to the tranny/clutch. If this proves to be reproducible in this condition, the candidates I had suggested to me with a recent whine (esp if it happens only after warm-up) were: belt and/or pulleys, vacuum leak, and coolant thermostat. In my particular case, the noise started at about 1,100 RPM and got progressively louder as I revved upward. And, indeed, it turned out to be a pulley bearing that wasn't rolling smoothly. YMMV, of course :)
 
#13 ·
I just got a call from the dealer that it's the belt tensioner pulley? IS that something that I could change easily myself? What is the reasonable quote that I can expect from the dealer? ....Oh and yes they have to order the part :)
 
#14 ·
noise

I have just posted a similar thread about a noise at 40-45 mph. I was also having difficulty pinpoint the noise. I put the vehicle on a lift, and accelerated the car to 45 mph.

I traced the noise to the differential. Between 45-40mph under no load there was a vibration were the drive shaft entered the differential.

I am in the process of exploring more info. The dealer was no help.
 
#15 ·
drbranko said:
I just got a call from the dealer that it's the belt tensioner pulley? IS that something that I could change easily myself? What is the reasonable quote that I can expect from the dealer? ....Oh and yes they have to order the part :)
That was my 1st guess ;)
Easy to do. Cost about $30 each.
One nearest power steer pump you can change just the bearings if you want $10.

Bazzle
 
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