How to demonstrate a vibration?

[Jeddy]

Please can anyone suggest a way of demonstrating a vibration on the accelerator pedal to a garage?

Basically it vibrates at speed on a smooth motorway, gets worse and is most noticable 70+, obviously it's difficult asking the tech guys to go over 70 so I need a way of proving / demonstrating there is a vibration (which they deny being able to feel, although one did at one point suggest he could feel something a bit like a tingle).

After driving for a while on a motorway it almost feels like my foot is 'going to sleep' as it does feel like a tingle, actually a high speed vibration, but fairly subtle.

The best I can think of is attaching some small jingle bells to the pedal, but I'm not sure they'd detect it, or that you'd hear it.

Any suggestions please, it's driving me nuts.

Thanks,
Jeddy

 

[Westheath]

If its the vehicle in your forum signature, C350e, then the throttle pedal is bolted to the floor and connected to the ecu via a wiring loom

If any vibration is present at speed then its present through the vehicle body then through the throttle pedal.

What mileage is it at ?

Check transmission bearings bushes.

Check wheels for warping, tryes for damage/distortion and wheel balance correction.

 

[Jeddy]

Correct, C350e.
12k miles.
I don't think it's anything like a warped wheel / flat spotted tyre, un-balanced wheel etc., as the vibration frequency is too high (frequency is similar to if you go too far right on a motorway onto the lane rumble strips, although if the tread on the sides of the tyre was raised, you know the ones every cm or 2, I'd believe that, but it's not). I did try increasing the tyre pressures out of interest, but no difference.
Thanks for the suggestion of transmission bearing bushes, I'll mention that next time it goes in, although my problem is currently getting the garage to believe me. I did suggest they did a temporary wheel swap but they didn't seem keen on that.
As an aside it happens regardless of whether the ICE is used (i.e. happens in E-mode). It's also definately not the haptic, this goes on for mile after mile, most noticable on a smooth motorway.
Any way I can demonstrate this?

 

[Westheath]

I wouldn't expect anything to be wrong with suspension or running gear if that's the correct mileage of 12k
But unless you know who owned the car before, and their driving habits, your better the devil you don't know.
However.............
Vibrational complaints are very subjective and need thorough testing by the workshop on a rolling road (drive train) and on the motorway, usually takes 2 or 3 people in the car and I've stuck someone in the boot before when there was a loose rear brake pad on a Rover Sterling a few years back (hardest one i ever had to find).
I always trust the customer when they complain of noises or faults that are sporadic intermittent or opinionated as they are the person who spends the most time in the vehicle and normally notices changes.

I also have customers that drive on wheel bearings that sound like cement mixers full of bricks but they cant all be perfect eh !!

 

[00slk]

Prop shaft centre bearing? Don't if this will have one, but had a similar vibration on a Vauxhall Mokka, no body could diagnose it until I was driven in it as a passenger.

 

[Jeddy]

I wouldn't expect anything to be wrong with suspension or running gear if that's the correct mileage of 12k
But unless you know who owned the car before, and their driving habits, your better the devil you don't know.
However.............
Vibrational complaints are very subjective and need thorough testing by the workshop on a rolling road (drive train) and on the motorway, usually takes 2 or 3 people in the car and I've stuck someone in the boot before when there was a loose rear brake pad on a Rover Sterling a few years back (hardest one i ever had to find).
I always trust the customer when they complain of noises or faults that are sporadic intermittent or opinionated as they are the person who spends the most time in the vehicle and normally notices changes.

I also have customers that drive on wheel bearings that sound like cement mixers full of bricks but they cant all be perfect eh !!

I agree that at that mileage nothing should be wrong mechanically, unless there has been an accident in its previous history which hasn't been repaired correctly / completely, there is even still a reasonable amount of wear left on the front tyres. I seem to recall checking the front tyres are originals (date check) so any accident wasn't bad enough to damage those, so unlikely to damage the wheels either (kerbing aside I guess but there is no evidence of that, so if applicable it's been fixed, but these aren't low profiles). The other thing I tried, given it has the air suspension, I have the problem regardless of setting of that, soft or firm.

You don't happen to work for a MB main dealer do you? South London near where you are perhaps? If so maybe I should book it in with you, sounds like you know your onions. Hampshire's not a million miles away and if I could get this fixed at the effort of travelling to S. London that wouldn't be a problem. Although the catch would be having a nice smooth 'motorway' nearby (I seem to recall half the M27 is concrete which probably wouldn't work).

 

[Jeddy]

Prop shaft centre bearing? Don't if this will have one, but had a similar vibration on a Vauxhall Mokka, no body could diagnose it until I was driven in it as a passenger.

Thanks for the suggestion.

 

[Jeddy]

Well, the jingle bells didn't help, however, while cleaning the car today I noticed that the outside of the front tyres and to a degree the rear weren't exactly smooth. I took it to my local tyre shop who confirmed that I had 'feathering' worse on the ftont drivers than passengers side. Apparently this can be due to manufacture, although Hankooks aren't exactly known for it (unlike some other makes), or it can be due to bad alignment.

 

[peterws1957]

Well, the jingle bells didn't help, however, while cleaning the car today I noticed that the outside of the front tyres and to a degree the rear weren't exactly smooth. I took it to my local tyre shop who confirmed that I had 'feathering' worse on the ftont drivers than passengers side. Apparently this can be due to manufacture, although Hankooks aren't exactly known for it (unlike some other makes), or it can be due to bad alignment.

Funnily enough I had the same problem as you describe on one of our daily drivers. My mechanic mate suggested swapping the front wheels round. Weirdly the problem was cured. Down I think to the wear pattern. I replaced the tyres anyway just to be sure and no problem since.

 

[L John]

After driving for a while on a motorway it almost feels like my foot is 'going to sleep'

Hopefully you'll get it sorted out by swapping wheels over as per Peterws, so the tyres run in the opposite direction.
Check tyres are not directional before doing this, directional tyres must be fitted to rotate in the correct direction for forward travel.
Don't you use cruise control on the motorway unless testing for this vibration?

 

[Jeddy]

Thanks peterws. I thought I'd considered that before but just realised I'd not thought it through! I knew the tyres had 'Outside' written on them, but of course that doesn't stop them being swapped left to right does it. D'oh!! I know I've had unidirectional tyres on my previous C350CDI and seem to recall they had a nice arrow on them which I can't see, so hopefully they're not.
Think I'll pop up to the tyre shop and get them swapped around. When I spoke to them the other day they did say that there was nothing wrong with the tyre per se and that it doesn't cause a problem it's just that it doesn't feel very nice, so I suspect if they swap them around and the problem goes away I'll leave it at that.
Very useful, again thanks, that's possibly saved me from buying a couple of tyres sooner than really needed.

L John, I'm not sure where you live, but the opportunity to use cruise control on motorways near me is rather limited, far too much traffic - I'd need adaptive cruise for that, but yes, once in a while I'm able to use it for a few minutes at a time. Having said which, even then I rest my foot on the accelerator pedal so that doesn't really help.

 

[L John]

I don't use motorways often but when I do, I'm happy to set cruise control at 72 if the roads are clear enough (actual real speed is 70) or 62 when there's a bit of traffic around. Busier still and I have been known to set it at 55.
I like to push the car a bit at times but motorways are no fun at any speed, even at 90, so I keep to the limits or well below because I set off in plenty of time for the journey instead of leaving it to the last minute.
People speeding don't bother me at all, I just don't feel the need to do it myself.

 

[Jeddy]

I don't use motorways often but when I do, I'm happy to set cruise control at 72 if the roads are clear enough (actual real speed is 70) or 62 when there's a bit of traffic around. Busier still and I have been known to set it at 55.
I like to push the car a bit at times but motorways are no fun at any speed, even at 90, so I keep to the limits or well below because I set off in plenty of time for the journey instead of leaving it to the last minute.
People speeding don't bother me at all, I just don't feel the need to do it myself.

I'm not sure I could easily use cruise at any speed for any length of time around here. I guess I could at 50, but that's going to annoy all the lorry drivers who have to pass me and the car drivers queueing behind them. Set at 60 in the inside lane and have to hit the brake when I approach the next vehicle waiting for a gap to pull out into. Trying to use cruise and change lanes becomes more effort for me than not using it. Having said which I think some do use it around here, I came up behind a car in the outside lane the other day doing around 65 who absolutely refused to pull over even when there were nice gaps in the middle lane to pull into. Oh well, as you say, motorways are no fun at any speed, thank heavens for podcasts etc..

 

[CrispArc]

Hi Jeddy,

Sorry to resurrect an old thread, just wondering if you had any luck swapping the tires/wheels around? I have a same issue with fine vibration noticeable through the accelerator pedal at speeds 65+ in a 2017 C350e.

MB have checked for loose panels during a service (my first assumption) but it seems all is in order under the car according to them.

Thanks in advance