Loud vibration at idle

RustyH · Post by **RustyH** » 23 Apr 2006, 04:19

My spouse's car is a 2000 S70 non-turbo AT which we bought new. It now has 74,000 miles, runs well. It's difficult to think back 6 years, but I believe when idling in Drive it has always been a little noisy with some vibration. Of late, the vibration is louder and needless to say, irritating for a $30,000 vehicle. I have been told this is inherent to this vehicle. My independent mechanic checked out my complaint recently and said this is normal for this vehicle.
The loud vibration doesn't start until we have reached a dead stop (traffic light). It stops the second we release the brake pedal. It also is considerably less when shifting into neutral when stopped.
It's up-to-date on service (i.e. 60,000 mile tune up). The top motor mount was partly torn and replaced (no change in loud vibration). Other mounts are OK per indy mechanic and dealer mechanic. I recently had a auto transmission service since the shift quality was not as smooth as when new. That didn't make a difference.
I'm presently doing a AutoRX treatment and ultimately plan to try Castrol Syntec 0W-30 (GC) motor oil to see if that might help quieten (and maybe smooth out) the engine (per Bobistheoilguy website). It did so in my BMW.
So, any ideas? Is this just inherent to this vehicle? If so, it's a bit undignified for such an expensive car. Otherwise, great car. We have never had to have anything repaired, just normal maintenance items.

vibbase · Post by **vibbase** » 23 Apr 2006, 05:53

Did you check the exhaust system alignment? The torque produced by the engine when in gear with the brakes on will tend to pull the the exhaust one way or the other. This can cause it to contact the frame rails or body if there is limited clearance to begin with. Putting the car in nuetral releases the torque and allows the engine to sit back again which would explain why the vibration stops.

Have someone sit in the car up on a hoist (properly blocked) start the car and put it in gear and observe what happens to the exhaust. Also look for areas along the exhaust where it may be contacting the body.

Hope this helps.

Post by **pfeener** » 23 Apr 2006, 06:05

I would go back to the motor mounts. You said the upper torque mount was replaced. Was it replaced with a Volvo mount or a solid urethane mount. The solid mounts last longer but do transmit more engine vibration. I would also consider having the lower RH mount replaced (under the timing belt) just to see if that helps. When that mounts goes bad the engine drops down a small amount and sits metal to metal on the two pieces of the mount. It will cause the symptom you're describing.