Idle vibration--What's next? 2000 S70 NA

RustyH · Post by **RustyH** » 15 Dec 2007, 14:03

The idle vibration/noise on my wife's 2000 S70 NA, auto, 85,000 miles drives me nuts. This has been happening for years now, but gradullay more noise and vibration. Idle vibration and noise is only when idling in D or if put in R, shifting to N will cause the vibation/noise to stop. Car drives well and in fact, gets relatively quieter at higher speed if you discount the tire and wind noise. Car is tuned up; I've cleaned the throttle body--all made the car smoother but did not eliminate the problem. All the motor mounts and torque mounts have been replaced (I did everything but the big hydraulic pads). Local dealer is not of much help; my indy mechanic is out of ideas. Dealer mechanic said exhaust sleeve was fine.
When braking to a stop, there is no noise or vibration, it starts about 1-2 sec after a complete standstill. It will stop as soon as the vehicle launches.
So, what's next? Could this be anything with brakes? ? transmission related (shifts are nice and smooth)
I saw an older posting about this problem and writer suggest replacing motor mounts, strut mounts and then putting rubber hose around front coil springs.
I have seen numerous postings about this same thing. Usually the recommendation is motor mounts. I saw a posting suggesting the brake vacuum pump (on a S40) may be bad.
By the way, idle speed per tachometer stays right at 800.
I called Volvo customer service since we are loyal Volvo owners, but rep would not refer me to the regional service rep. My local dealer said he would refer me, but since we had a falling out this summer, I'm sure he didn't.
Any ideas would be appreciated.

Post by **Ozark Lee** » 15 Dec 2007, 14:50

Is it a vibration feel or a rattle sound that is bothering you?

Since it starts after you come to a stop I would rule out the brakes immediately.

If it is a rattling sound I would check the heat shields around the exhaust. My son's car rattled like crazy and I tracked it down to a heat shield near the fuel tank. Another popular culprit is the shield on the bottom of the car above the catalytic converter.

We silenced it forever (or at least until the hose clamp breaks) by simply putting a big hose clamp around the shield and clamping it to the exhaust pipe.

If none of those check out let the car cool down and then rap on the catalytic converter and listen for noise. It shouldn't make anything more than a thud.

I had a catalytic converter melt down on my wife's old Jeep and it rattled badly at idle. Once I removed it and shook it around it sounded like it was full of gravel.

...Lee

RustyH · Post by **RustyH** » 15 Dec 2007, 16:35

I wouldn't call it a rattle. It's a very low pitched noise with a slight vibration. The intensity varies. When particularly bad, you think you are in a diesel truck idling. Immediately popping into Neutral and it's gone.

tripleb · Post by **tripleb** » 15 Dec 2007, 17:12

It sounds like a mount problem.

The hydraulic mounts sag as they get old, and cause the transmission to contact the rubber stop on the subframe. If you have someone start the car and put in D, then look under the trans. close to where the A-arm is bolted to the subframe and you can see if the trans. is contacting the rubber stop. If it is, you need to replace the hydraulic mounts.

Have you replaced the mount under the front of the engine?

What about the torque rod on the bottom of the engine?

Good Luck,

3B

RustyH · Post by **RustyH** » 15 Dec 2007, 17:29

Thanks, tripleb. I too kept thinking that this has to be a mounting problem. I replaced or had mechanic replace the following:
Driver's top strut mount, it has the rectangular bushing
The piece on the firewall where the top strut mount connects
Right lower mount near crankcase pulley
Transmission torque strap
Both the big hydraulic mounts (pads) front and rear

I don't believe there are any more.
Could collapsed subframe bushings do this?