A6 4.2 Q Avant "I'm picking up bad vibrations..."

[peterhindle]

Anyone had a problem like this?

I have an A6 Avant, 4.2 Quattro, MY '99, 70k miles. Over the last month or so, I've become more aware of a high-frequency vibration (detectable through the floor, and even through the steering wheel), which seems to be related to engine speed (worse at some rpm, less noticeable at others). When the vibration problem started, it was intermittent, and I thought (hoped) it was caused by the road surface.

However, the vibration has now become constant. The mechanic (who seems highly competent , and who has previously worked on the car) thinks the problem may be caused by a hydraulic engine mount that's leaked and lost its fluid, thus passing engine vibrations through to the chassis.

Does this seem plausible? The initially intermittent nature of the problem gives me cause for doubt, but - then again - what the hell do I know?

Your contributions would be much appreciated.

Peter

(Incidentally, it's a bloody brilliant car - even when [ridiculous exaggeration] it's shaking the fillings out of my teeth.[/ridiculous exaggeration])

[charlie61]

not lost a weight off a wheel have you, or hit a pothole and buckled a wheel, I put 18" RS6 alloys on my avant, within a week i'd put a flat spot on one of them which caused a vibration at speed that made me feel sick, a re-balance cured it

[peterhindle]

Thanks for the response. No, unfortunately, it's not a wheel problem - the vibration's there even when the car's stationary.

[Edd_W]

That is bad news. Any engine vibration could be expensive to fix. Does the engine feel like it is missing or rough at all if you gently rev it while stationary?

Some smal harmonic vibrations are normal but it should not be felt in the cabin. If so, I would start by VAG-COM'ing it to see if there are any codes which may point to the problem.

There is a VAG-COM locator at audiworld

.com if you do a search, there are quite a few around - roughly where are you located?

[peterhindle]

Many thanks!

The engine sounds fine; there's no audible vibration, and I'm sure it's firing on all cylinders. It took the mechanic a little while before he could see (well, actually, feel ) what I meant. The problem is certainly more detectable when the engine's having to work harder (e.g. climbing a steep slope).

Excellent idea about a VAG-COM check. I'm in West Sussex - thanks for the tip about audiworld.com

[Edd_W]

It does begin to sound like it is a drivetrain problem because that would show up more when under load.

It could be a bent driveshaft or a prop-shaft mounting failing?

Difficult to diagnose without being in the car.

[peterhindle]

End of the story? Engine mounts were changed, slightly reducing the vibration. Eventually, the car went to the local Audi dealer, who has diagnosed two fragmented catalytic converters . Cost to replace? More than £2,000.

Oh dear.

[BenjaminTDI]

[ QUOTE ]

End of the story? Engine mounts were changed, slightly reducing the vibration. Eventually, the car went to the local Audi dealer, who has diagnosed two fragmented catalytic converters . Cost to replace? More than £2,000.

Oh dear.

[/ QUOTE ]

Good lord these cars cost so much to run!! At least it's sorted now.