JayTeeC63

Anytime I let off the gas when I'm driving 20+ mph I hear a distinct whirring sound that sounds like it's coming from the back of the car. At first I thought something might be rubbing against a tire so I took to MB Service got a balance, alignment and a road force test. Nothing was wrong. Service advisor said everything was fine with the wheels/tires. I started hearing this problem after I went a little too fast around a corner and skirted off into the grass, breaking the beads in my tires. I took the tires off myself and cleaned the wheels off, put the tires back on. I don't know if it's abnormal or not. Has anyone else had an issue like this? I can't find any similar noises in videos anywhere

Adam Chambers

LSD?

Alex.currie44

The fuel pump I believe - someone will correct me if I am wrong I am sure - is under the right rear seat. Could one possibility be that it is starting to show its age and struggling to keep up above 20 mph?

Is it a situation where the sound changes pitch as the car slows down?

JayTeeC63

I don't think it's showing it's age due to the fact it's only has 17K miles on it. It's louder and sounds like a "tighter" whirring noise the faster I'm going. When decelerating it progressively "spaces out"

Alex.currie44

So you are saying it winds up as you go faster i.e. the frequency increases and decreases with speed.
How about a wheel bearing?
When I test drove my car 6 weeks ago it was raining in Vancouver and traffic was a ***** so getting it up to highway speed was impossible. I bought the car - it was a swap for a CLA45 AMG - and later that day found it had a noise that started at 100kph as a harmonical sound that increases in frequency and disappeared at 125kph. I suspected a wheel bearing.
I had the car checked completely by my trusted tech and the left front wheel bearing was on its way out. He changed both fronts under warranty.

JayTeeC63

It could be a wheel bearing but don't you think that's something a certified MB tech would notice during a simple alignment and balance? Thank you for your help on this by the way

Alex.currie44

Not likely. A good experienced tech will be able to hear it if he drives it or if he hangs it on a hoist and sits in the car or has someone in the driver's seat and has it brought up to speed
You should try to narrow down the range from the lowest speed you hear it to a point where you can no longer hear it.
My front bearing experience was interesting. As the car was turned left it got noisier. To the right it went quiet at the speeds I noted earlier. If it is a bearing they will change the whole hub assembly of course but try to argue they do both sides given one has failed under warranty. I didn't even have to suggest that to my guys.
The other thing that is bugging me is you say it comes on when you take your foot off the gas. Perhaps it is a drive shaft issue with the rear disc.

Diabolis

I don't know whether you guys missed it, but the OP indicated that it happened after an off-track (or off-street) excursion... that was obviously violent enough to pop the tires off the beads. That's a rather serious lateral impact to the rear wheels, suspension components and drive linkage including the LSD, so its very likely to be one of those components. Eliminate what they have checked at the MB shop... which definitely leaves you with wheel bearings (unless they are completely disintegrated, there are no obvious signs that they are shot when the car is up on a hoist) or the LSD itself. You could have even slighty bent the rear subframe and/or killed the bushings. Your best bet is to tell the shop exactly which way the car slid and went off the road as that would allow them to look at things that would never fail as a result of normal use or wear and tear... and contrary to Alex.Currie44's advice, please don't even think about trying to sneak it in as a warrantly claim. Damage sustained as a result of an impact is NOT covered by warranty, period.

Alex.currie44

You will have to help me out here. I went back and there is only one page on this post and the OP is #1 and Diabolis you appear to be #5. I can see nothing that says this was a result of an off road excursion. Of course you would be correct if what you are saying is what happened but I am having trouble connecting what the OP said and the off road issue. Can you clarify where you got that info please?

Mort

Reading comprehension 101...lol

See post #1

Alex.currie44

I didn't read anything about any lateral impact with a fixed object here, just a slide across some grass which could break a low profile tire loose from its bead without huge mechanical loads. I didn't read anything all that sinister into what he described.
We have no idea as to how fast he might have been going either
You would think if the force was a high as is being suggested something would have come up bent or seriously misaligned when he had it checked.
Perhaps we need the OP to tell us more of the circumstances. I guess it would also be wrong to assume he had a 4 wheel alignment done to check the thrust angle etc. in the rear after his excursion.

Diabolis

Alex - my sincere apologies if you didn't catch the "skirted off into the grass, breaking the beads in my tires" part and also don't know how much force is required to pop the beads on two inflated tires. I did not mean to suggest dishonesty if none was intended on your part, and I am sorry if I offended you.

As for the impact itself, I do know how much force is required to pop the beads on a tire... I've done it twice on a track car when either the front or the rear slid sideways over the curbing and into the ground on the outside. In both cases there was other damage - snapped tie rod, ball joints and bent control arm on the front, and snapped drive shaft, wheel bearing and damage to the LSD on the rear. While suspension and drivetrain components are designed to take bumps vertically, they are not designed to have much flexibility laterally so a reasonably strong whack sideways certainly has the ability to damage other things.

thesaintusa

I would agree that it might be quite an impressive off-track/road excursion to pop the bead of a tire.

I have had 2 off track excursions at high speeds (100+mph) that have damaged suspension components and not popped a bead on a tire I have also had the misfortune of an off-track mishap with no issues at all.

Having a tire come off the wheel/popping the bead can be associated with significant suspension component issues.


Any chance that there is 'dirt/grass' in the tire from the off track excusion? i.e. did you just have the tire remounted without removing it from the wheel completely?

Alex.currie44

No worries mate. I am still wondering what actually popped the tires off. I had it happen years ago on a slide but not recently. He said he removed the tires, cleaned what I assume is grass off himself and remounted the tires and other than this noise all seems ok. I guess we will have to wait until he gets it inspected for bearing failures etc.

JayTeeC63

Thank you everyone for replying... Have not checked this forum in quite some time. It was a wheel bearing issue and it was covered under factory warranty... which I am now out of lol