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2001 SLK320 grinding metallic noise in the rear (or front?) on minimal acceleration

6K views 16 replies 5 participants last post by  blackslk320 
#1 ·
Hey all, I have been on the forum most of the day trying to figure out this problem and I am still unsure. I read that it could be something to deal with the cam etc.

Here's my issue, this only happens under LOW acceleration...pulling from a red light for example...around what seems to be 2300 to 2600 rpms. At this point it sounds like a metallic grinding noise, and it goes higher in frequency/tone if I keep accelerating at the same rate and then goes away at around 2600. If when I hear the sound I then push the accelerator in even SLIGHTLY, the noise goes away.

It sounds like the noise is coming from the rear, but this car is so small that it could be coming from the front/engine that I don't realize it.

Any ideas? Thanks for any help. It's a 2001 SLK320. Loving it so far.

-Matt
 
#6 ·
I've had something similar, but it may not be the same. I've had my 320 for (almost) 10 years now, and since year 2 or 3, I've had a loud clicking under light acceleration (about 2k-3.5k RPM) that seemed to almost come from under the driver's seat. When it was still under warranty, I took it to the local dealer, who diagnosed it as a bad catalytic converter and replaced it. Didn't solve the problem. Every now an then, I still get the loud clicking. Doesn't seem to have caused any problems, so I just let it go.

If anyone else has had similar or know what this is (and/or thinks I should be concerned) let me know. Otherwise, it may just be a quirk of the car.
 
#9 ·
So...I brought my buddy out in the car to see what he thought about the noise...he said it sounds as if a solenoid is opening/closing. Not sure for what, but it seems it happens at/around 45 mph. Possibly when under low acceleration the process happens slower making it audible, but when you are accelerating slower it happens faster and can't hear it. It definitely sounds like it's coming from the drivers side rear...maybe a lock for the roof. I don't know. The first question he had when he heard it was "do you have one of those wings that pops up when you are at high speeds? (like a porsche)...that might help to visualize the sound I am hearing.

This is just a guess and I am hoping to hear some insight from all of you about it.
 
#10 ·
did you happen to get new wheels installed recently?
this is probably unrelated... but when I placed some new wheels, the lugnuts were too long... resulting in a click click click when starting off. For some reason, at higher speeds, it would stop clicking (perhaps then a continuous sound that I could not discern). Anyways, After replacing the lugnuts, all was well.

good luck
 
#11 ·
hmmm, that is good thinking, i did have to replace my drivers side rim and the sound did seem to start after that...but i replaced it with the same AMG rim as was on there before...had america's tire install. How would I check to see if this was the problem?
 
#16 · (Edited)
well... BINGO
i am pretty sure it is the lug nut then. The lug nut is just a bit too long and hitting some part within the rotor as it spins. I believe it was part of the brake system (why inside the rotor, I do not know). I would change this as soon possible as who knows what kind of damage is going on inside.

Let me know how it turns out.

this thread may be of interest:
http://www.benzworld.org/forums/r170-slk-class/1284837-spare-tire-wrong-bolts-damage.html
 
#17 ·
I can check it out, but the rim is the same rim (AMG) that was on there originally and the sound is literally at a specific speed and not all the time. I will still check it out though. Wheels never lock.
 
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