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E39 suspension problem

I am experiencing a strange problem which what I believe is my front suspension. When going over rough road while braking lightly, the suspension seems to go into resonance and the ABS cuts in even after leaving the rough surface. Doing the same thing without braking, it resonates - but less so. Braking while driving down a rough relatively steep incline is where is is most noticeable. I thought at first it was something to do with the ABS but I now think the ABS is a symptom of the suspension issue. The MOT garage tell me the suspension is OK and it (apart from said fault) drives OK. Is thing indicative of something I am missing?

Reply to
DCA
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"DCA" wrote

I'm guessing a wheel-speed sensor (ABS/DSC/etc.) is flakey, or has a loose connection.

FloydR

Reply to
Floyd Rogers

I thought this too but as the resonance problem is also present when not braking I doubt it albeit braking makes it worse. If the wheel is bouncing during the suspension resonance, the ABS may mistake it for locking up?

Reply to
DCA

E39's just seem to do this under certain situations. It may be made worse by wear in the front suspension components (bushings and ball-joints) and by low-profile stiff sidewall tires. Some E39's seem prone to it - some aren't.

If you have over 60,000 miles on your car - it needs new front lower control arm bushings, and the ball joints at the end of these arms may also be worn. Common and predictable - also leads to a shimmy at 60-70 MPH that can't be solved by tire balance.

Reply to
admin

Check a specific E39 resource or maybe even

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Wear in the suspension can cause symptoms even if everything looks alright upon inspection.

Reply to
adder1969

thanks for this info. Useful. Is there any more detailed info on it as I can't find any! Perhaps I am searched on the won key words. Mileage is 80K an it has a 3.0d lump in it. What about shock absorbers? resonance seems consistent with some sort of failure with the shocks (although generally, the ride is OK). Perhaps the bumps hit a certain repetition rate to spark if off?

Reply to
DCA

Certainly shock absorbers are also part of the equation. The 5 series has been known for superb handling and ride qualities - they got this way by having very compliant front end components. If some of the components get too compliant there is always the possibility the suspension won't behave the way it was designed to. Putting any of the components back towards the factory configuration will help eliminate any suspension movements that are out of the expected range.

Do a search on Yahoo groups for E39 - you may find help there.

Reply to
admin

Traction control cutting in too?

Reply to
Robin

Good question. I 'think' I recall seeing the DSG light illuminate but will monitor more closely (I'm usually trying to see the road surface for specific causes!)

Reply to
DCA

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