E320CDI 80mph Bump, Bump, Bump ......

[clive williams]

I wasn't sure where to post this thread but I came to the conclusion that it was about driving pleasure more than anything else.

Anyway, I bought an E320CDI T210 two months ago but its only just recently that the missus has let me use it occasionally. I've noticed that on a cruise down the motorway at about 80mph the car has a pronouced feel that its driving over a wash board surface. The effect only occurs between 80-85mph on a light throttle opening. Above or below those speeds it instantly disappears. It also disappears on the overrun and on a loaded throttle such as overtaking or on the hills. There are no normal transmission vibrations and the sensation appears through the steering and body.

I can't decide whether its suspension related or engine related but its unpleasant especially as it occurs at the most comfortable motorway cruising speed. I half think that there must be a sympathetic resonance with the road surface, in which case is this a mechanical failure or a design fault?

Any thoughts or discussion would be appreciated.

Clive

500E
E320CDIT210

 

[996jimbo]

Does it occur on all surfaces? Can you reproduce the effect at same revs in different gears?

Poor rear shocks can cause / allow the resonance but it would vary with the surface finish. If it is engine related then you could expect it to show up at particular revs rather then particular speeds.

Just my thoughts - good luck with it!

 

[jberks]

If it's engine load/ road speed related then it rules out the usual suspects of balance/track. The only things I can think of that would vibrate at certain road speeds but would settle down under throttle load are prop shaft or engine/gearbox mounts. I believe the engine mounts are known to cause issues on the 210 so they may be a candidiate.

 

[clive williams]

Jimbo, Jberks,

Thanks for the thoughts, much appreciated.
I've only been able to try it up and down the MI between J23 and J26. The surfaces are fairly consistent and I've never noticed it with any other car in hours of pounding this particular part of the Slab. I'll see if I can wrest the motor from the missus and find an excuse to do the M69 where I know of a very smooooth section.
I take the point about engine mounts - are these hydraulic or good old fashioned rubber? But if it was mounts I would have expected a wider range of revs/loads and tend to show up under acceleration rather than steady state light throttle? I will take a look this weekend although I have never tested hydraulic mounts.
I'll post any results

Clive

500E
E320CDIT210

 

[maddog]

I had a problem on my W210 a while back, one of the tyres developed a large bump in the middle of the tread causing a vibration at around 30mph .

My local tyre chap had a good look at it and blamed a combination of heavy car and gravel drive.

It seemed that a split had occured on the tyre probably due to being parked on gravel and the steel banding had corroded swelling it a bit causing the bump.

 

[clive williams]

Thanks Maddog,

I don't think its a blistered tyre as that would probably be speed sensitive, starting slowly and building frequency as the speed increases. I've had this happen before and the probem were discussing is not the same.
Thanks for the thought though.

Clive

500E
E320CDIT210

 

[malcolm E53 AMG]

Sounds very much like soggy suspension. A check on front anti-roll bar bushes, steering ball joints and track rod ends would be a good starting point. I once rebushed the front end of a car and couldn't believe the difference it made to the handling.

Another area to check are the engine undertrays especially the front one directly beneath the bumper to make sure they are present and that the front one is aerodynamically sound. Air pressure under the car at some speeds can induce what you describe.

 

[guydewdney]

driveshaft / propshaft main bearing gone?

 

[television]

I go along with prop shaft out of balance or center bearing/spider

Malcolm

 

[clive williams]

Thanks Malcolm210,

I'll look at the bushes this weekend. I go along wholeheartedly with you on the subject of the effect of new bushes. I'll probably go down that route if there is a hint that they have degraded even if it doesn't solve the problem as its a ponderous old barge and I'd like to sharpen the handling.

Guy/Malcolm

Thanks for the thought about the prop/main bearing - its another thing to check but if it is it will obviouly still be there at steady throttle if I shift down a gear and maintain speed. Easy one to try. It can't be too bad as the motor came with a 12 month ticket on it via Andy Gayle (B'ham indie)

The undertray will be checked when I do the bushes.

With all these suggestions I'll be a busy bunny this weekend.

thanks

Clive

500E
E320CDIT210

 

[vics1982]

Hi,

it may be that your wheels need balancing and tracking.
I had that on mine last week, does it continue up wards from 80/85mph?

 

[clive williams]

Hi Vics,

I doubt if its balancing or tracking. If its balancing then I would have expected it to have occurred at a lower speed say, 50-60mph and shaken the wheel from side to side. Also, it would have increased/decreased steadily as you get the critical speed albeit within a specific band. This comes in suddenly at 80mph and disappears as quickly at 85mph on a constant light throttle. It also disappears when the throttle load is increased or decreased, which makes it throttle load sensitive.

Tracking is a thought but there are no tell tale signs on the tyres even when you rub your hand over the surface to detect feathering.

I couldn't try the motor out this w/e as we had a fair bit of fog around on the motorways but the missus is away for two days so that gives me another chance to play.

Clive

500E
E320CDIT210

 

[clive williams]

bump, bump, bump ...... gone

A quick update. The fitment of new (winter) tyres has cured the strange vibes. The motor now cruises silently and sirenely. It's gotta be those P6000s - I've must have a real downer on them.

Clive

500E
E320CDIT210

 

[maddog]

A quick update. The fitment of new (winter) tyres has cured the strange vibes. The motor now cruises silently and sirenely. It's gotta be those P6000s - I've must have a real downer on them.

Clive

500E
E320CDIT210

told you tyres!!

 

[clive williams]

told you tyres!!

Maddog,

Yes I concede. I've got 3 of the 4 tyres still and there are no noticeable blisters. as it happened with very specific criteria (80mph, light throttle) it must have been a small blister. Still doesn't change my prejudice against P6000s.

Clive

500E
E320CDIT210 smoooooth now

 

[maddog]

Maddog,

Yes I concede. I've got 3 of the 4 tyres still and there are no noticeable blisters. as it happened with very specific criteria (80mph, light throttle) it must have been a small blister. Still doesn't change my prejudice against P6000s.

Clive

500E
E320CDIT210 smoooooth now

not its not the tyres mine were Michelin pilot sports that i had a problem with it the weight of the car and way this can force stones between the treads, its big car quirk rather than tyre of make specific problem

Mine on did it at 30mph was fine at all other speeds and was also far better on the rear than front.