Intermittent Noise - MB Can't diagnose

[Beancounter]

So, had the GL350 (X166) for just coming up a year now and it's been great, 18,000 miles, no problems

BUT.....

Background.....about 4 weeks ago, first service carried out, then a few days later 2 new rear tyres put on. Car had PZero's and I went with 2 brand new Toyo's (exactly the right spec) this time having had them on my RRSport and never really been a fan of the PZero's on the GL. Nothing unusual at this point.

Then, we now get an intermittent sound from under the car, sounds like you are driving through a short puddle and water is hitting the wheel arch -it's not, it does it on dry roads, feels like the front wheel is being 'grabbed' for a millisecond. First time it did it at 70mph and put the car off balance. It then did it at around 50mph when backing off the accelerator.

Car was recovered and I even managed to recreate for the MB Assist tech. Car went to MB and they couldn't find anything, even when I went in to road test - no errors are showing on any data, even data they sent to MB Germany (or so they tell me).

I get the car back, it still does it, probably 2-3 times in a 50 mile trip. Quite un-nerving. Car has been back 2 further times to MB and they are telling me nothing is wrong. They are saying I should now replace the 2 front tyres with Toyo's as that could be causing the traction control to intervene because of the difference in tread depths and tread patterns (front 3.5mm, rear 7mm). Is this really a genuine diagnosis.

Stuck between a rock and hard place currently as until I can recreate with the MB Service team, they won't do anything.

Any thoughts from anyone who may have had something similar?

Thanks in advance

 

[219]

In fairness , I have heard of differences in rolling radii between front and rear causing problems with electronics led cars - diagnosis may be correct , rotation of tyres every X000 miles to achieve even wear may in fact be needed .

 

[stewslash]

Id turn your traction control off and see if you can recreate the issue if not then id say Merc techs are correct

 

[tonysmb]

I'd say that it was quite possible.

I'm not familiar with the GL's set-up, but if the TC works from ABS-sensor readings, then it could well be intervening by momentarily applying the brake on the fastest rotating wheel, ie the one with the more worn tyre, as the system will be 'seeing' a skid/slippage situation.

With some 4x4s, ie Freelanders, it is strongly recommended to replace tyres in full sets otherwise there's a risk of potential transmission issues.

 

[Bobby Dazzler]

Before I reached the end of your first post I was thinking the difference in tyre tread and depth could be causing it. Even if it's not the cause, and it doesn't fix the issueit probably is the next thing on the list to eliminate.

 

[wu56Shoozz]

I was a fan of the Toyo tyre but..after a long hard time with them especially in a car (VW) that had 17"s and low profile tyre.. I decided to change to Uniroyals.. and ..trust me the car was miles quieter than before the slight judder that I always had despite numerous balances was all gone.. could have been a bad batch, bad tyre what ever, but it may be due to the tyre.. just sayin' like..

 

[Beancounter]

Ok thanks for the responses guys, really is appreciated.

Good idea to turn the TC off and see if it happens, I'll try that.

Have got two new front Toyo's on order so as said decided that was the best way to hopefully eliminate the problem.

I'll try the above and let you know how I get on. Thanks again.

 

[Bobby Dazzler]

Ok thanks for the responses guys, really is appreciated.

Good idea to turn the TC off and see if it happens, I'll try that.

Have got two new front Toyo's on order so as said decided that was the best way to hopefully eliminate the problem.

I'll try the above and let you know how I get on. Thanks again.

Providing that it's safe to do so, switching the ESP off may test it, but I'm not convinced, because the car will still intervene if it thinks there's a risk losing control. Worth a try though.

Have you checked tyre pressures? Another one to eliminate.

 

[Beancounter]

Providing that it's safe to do so, switching the ESP off may test it, but I'm not convinced, because the car will still intervene if it thinks there's a risk losing control. Worth a try though.

Have you checked tyre pressures? Another one to eliminate.

Thanks. Yes, I've checked the pressures (I deflated about 10 PSI then re-inflated again) and tightened the wheel bolts so that they are torqued correctly.

I'm wondering if there could also be a little debris behind the caliper causing a problem so will give it a blast with my compressor with the wheel off too.

 

[PobodY]

A difference of a couple of mm of tread depth is nothing. - If that's really the root cause of the problem, I'd suggest that the AWD system is too sensitive and perhaps unfit for purpose.

Hyundai frequently use this excuse for issues with the Santa Fe, but unless there's completely different wheel sizes it doesn't bare scrutiny (and it's almost always something else).

 

[grober]

As one Montgomery Scott might have said "I cannae change the laws of physics Jim".
I doubt that many owners of modern large heavy 4x4 vehicles with high ground clearance/high centre of gravity realise just how much electronic vehicle stability intervention constantly goes on in the background to enable their vehicles to drive like ordinary saloon cars. Whether its their abs/stability control or active suspension combating the inherent instability of these vehicles it only becomes apparent when these fail to operate correctly. Since this change appears to date from a time the tyres were changed that would be the obvious first port of call. Does it have airmatic and active curve control option for example?

 

[Beancounter]

As one Montgomery Scott might have said "I cannae change the laws of physics Jim".
I doubt that many owners of modern large heavy 4x4 vehicles with high ground clearance/high centre of gravity realise just how much electronic vehicle stability intervention constantly goes on in the background to enable their vehicles to drive like ordinary saloon cars. Whether its their abs/stability control or active suspension combating the inherent instability of these vehicles it only becomes apparent when these fail to operate correctly. Since this change appears to date from a time the tyres were changed that would be the obvious first port of call. Does it have airmatic and active curve control option for example?

Thanks, no it doesn't have the active curve option, just the air suspension. You're right, the tyres do seem to stick out as the point of change, so hopefully new front boots will rectify the problem, though as a counter argument, I had a tyres get a rip in it a require replacement at a bout 10k miles, at that point one tyre would have had considerably more tread than the others but no problem was exhibited - maybe the difference in Pirelli/Toyo tread pattern is amplifying the issue now though.

 

[grober]

Since rereading your first post I did notice the car was also serviced recently?? No chance some sensor was damaged/dislodged during the service or any routine software "upgrade" done?

 

[Beancounter]

Since rereading your first post I did notice the car was also serviced recently?? No chance some sensor was damaged/dislodged during the service or any routine software "upgrade" done?

To be honest, this was my first port of call with the servicing dealer, but there has been, as you would expect, a complete denial that anything was done apart from an oil change and a satnav map update.

I've just booked the car in for a hunter alignment at the weekend (worth the £40) to see if there are any issues there. Will hopefully have the new tyres by then. If it still does it after that, then I think I have just cause to say to MB it's their problem as I would have done all their suggestions.

 

[BlackC55]

It does dound like the ESP is triggering. It happens sometimes if there is a speed sensor issue (that will bring a code up) or there is a different rolling radius between front and rear.

The dealers advice is correct IIRC to start with.

 

[tonysmb]

To be honest, this was my first port of call with the servicing dealer, but there has been, as you would expect, a complete denial that anything was done apart from an oil change and a satnav map update.

I've just booked the car in for a hunter alignment at the weekend (worth the £40) to see if there are any issues there. Will hopefully have the new tyres by then. If it still does it after that, then I think I have just cause to say to MB it's their problem as I would have done all their suggestions.

Re the service, if it was the car's first service, and an A service, then unless the GL is any different, which I doubt, they don't even take the wheels off. It is simply change oil & filter and check this/that.

They probably spend as much time adding up the invoice as they do servicing.

 

[tonysmb]

Just a thought, are the new tyres directional? If so, I presume that they've been fitted the correct way.

I don't think it would result in your symptoms, but it wouldn't be the first time.

 

[Beancounter]

Just a thought, are the new tyres directional? If so, I presume that they've been fitted the correct way.

I don't think it would result in your symptoms, but it wouldn't be the first time.

Yes, checked that, but a valid suggestion. 'Outside' is fitted correctly to both new ones and I'll check, but don't believe they are directional.

 

[Beancounter]

Sorry for the lack of update.

Got around to fitting the matching front Toyo's and had the alignment done at the same time.

To say it was 'out' would be a massive understatement Front and rear was a sea of red on the first report, camber, toe etc. Had it all corrected and the car is now spot on . Added bonus is that the Toyo's feel a lot nicer to drive than the PZero's too.

Clearly these things have very sensitive tollerances, so lesson learnt. Will update on the wear of the Toyo's in a month or so.

Thanks for all the suggestions earlier in the thread