Problem with vibrations since workshop

[Smallblock454]

Hi,

my 2003 986 was at a workshop. Since than i have problems with vibrations in the drivers footwell. The vibrations appear to come from the footwell floor / side panel and appear also in the gas pedal (which in my car is electronic – so no throttle cable).

The vibrations are engine related. They disaapear immediately if i press the clutch and the rpms drop.

The car was in the workshop to do:
DMF, clutch, pressure plate, release bearing, clutch servo spring
Water pump, thermostate
IMSB
Front engine mount
and some other things

I also asked them top check the 2 other hydro engine mounts. They didn't do that. They've said that they never fail, hm...

They said there are no vibrations or that they cannot feel any unusual vibrations. All of these cars would vibrate, blah blah...

In the end they replaced again:
DMF, clutch, pressure plate, release bearing
Water pump, thermostate
and put in an old engine front mount in

The IMSB (open roller bearing) wasn't replaced.

The vibrations in the footwell are still there. Additionally i now have vibrations in the drivers seat and centre console.

The vibrations start at aound 2.000 rpm and disappear above around 4.500 rpms. The vibrations appear under light to heavy load. No appearance with no engine load. They are definitely not undercarriage related.

I suspect there is a problem with the engine mounts or that the drive train is tensed in some way. Or that there was something going wrong, when they installed the IMSB.

Has anybody experienced similar vibrations from the engine in the drivers footwell?

Thanks and regards

[911monty]

Sorry to hear after all that work. Sounds like could be clutch related so I notice one thing missing in the clutch system. Did the pilot bearing get changed either time?

[Smallblock454]

You mean the pilot bearing of the transmission input shaft? That wasn't replaced.

But they replaced the clutch relaese bearing two times.

The vibrations in the footwell showed up first, after the workshop did the initial repair on the clutch and so on.

[911monty]

Originally Posted by Smallblock454

You mean the pilot bearing of the transmission input shaft? That wasn't replaced.

But they replaced the clutch relaese bearing two times.

The vibrations in the footwell showed up first, after the workshop did the initial repair on the clutch and so on.

Hopefully not but I suspect the pilot bearing. Attached is a procedure to check wether the problem is the release or pilot bearing.
Start with a road test of the vehicle. Listen for noise with the transmission in gear and the clutch pedal to the floor. Next release the clutch with the transmission in first gear. Noise under this condition indicates a worn release bearing or a worn pilot bearing.

To isolate the two, keep the clutch pedal on the floor and shift the transmission into neutral. If the noise persists, the release bearing is bad. If the noise is gone, the pilot bearing is bad.

A bearing noise that occurs when releasing the clutch pedal to engage the clutch while in neutral, but goes away when the pedal is depressed is caused by a bad transmission input shaft bearing.

Hope this helps

[Starter986]

old engine front mount

[Racer Boy]

Originally Posted by Starter986

old engine front mount

That is where I would start. Or rather have the workshop start!

[Smallblock454]

@911monty:

The issue i have is vibrations, not noise.

The vibrations apperar in the drivers footwell area.

Meanwhile the vibrations also appear when the engine is not under load. Before they only appeared when the engine was under slight load.

Since they've changed the front motor mount to an old one i also have vibrations in the seat and in the centre console / gear shifter.

Noneheless i've checked the procedure you've described today, but couldn't find any noise or behavior that was there, before i brought the car to the workshop to do the repairs.

What i can tell is, that the vibrations are definitely engine related. If i press the clutch the vibrations go away as soon as the rpm drop. If i press the clutch and try to hold the rpms at the same level, which is a bit tricky because the engine has to be under a slight load, the vibrations are still there.

@Starter986 and @RacerBoy

The new engine mount has a 987 parts number and the covers on the side are different. The original 986 engine mount has a rubber cover on each side. The 987 engine mount has rubber and foam compound cover on each side.

Porsche said that this is the right updated motor mount for this 986, but we (i and the workshop) were not shure. Now i am shure that this new 987 front motor mount works much better than the old use one, because i now have vibrations in the seat. So i'm shure they go away if they install the new mount. And now i know that the 987 front motor mount seems not to be responsible for the engine related vibrations in the footwell.

Unfortunalety my main problem the engine related vibrations in the footwell is not solved. And i hate these vibrations. I know that the reception of vibrations are a very individual thing. To me it's a very unpleasant kind of vibration. I have no more fun when driving the car.

Before the car was concerning the engine was for me completely vibration free. OK, some light shaking in the seat when standing at the traffic lights, but no engine related vibrations above idle. So i'm a kind of desperate at the moment.

[BYprodriver]

Originally Posted by Smallblock454

@911monty:

The issue i have is vibrations, not noise.

The vibrations apperar in the drivers footwell area.

Meanwhile the vibrations also appear when the engine is not under load. Before they only appeared when the engine was under slight load.

Since they've changed the front motor mount to an old one i also have vibrations in the seat and in the centre console / gear shifter.

Noneheless i've checked the procedure you've described today, but couldn't find any noise or behavior that was there, before i brought the car to the workshop to do the repairs.

What i can tell is, that the vibrations are definitely engine related. If i press the clutch the vibrations go away as soon as the rpm drop. If i press the clutch and try to hold the rpms at the same level, which is a bit tricky because the engine has to be under a slight load, the vibrations are still there.

@Starter986 and @RacerBoy

The new engine mount has a 987 parts number and the covers on the side are different. The original 986 engine mount has a rubber cover on each side. The 987 engine mount has rubber and foam compound cover on each side.

Porsche said that this is the right updated motor mount for this 986, but we (i and the workshop) were not shure. Now i am shure that this new 987 front motor mount works much better than the old use one, because i now have vibrations in the seat. So i'm shure they go away if they install the new mount. And now i know that the 987 front motor mount seems not to be responsible for the engine related vibrations in the footwell.

Unfortunalety my main problem the engine related vibrations in the footwell is not solved. And i hate these vibrations. I know that the reception of vibrations are a very individual thing. To me it's a very unpleasant kind of vibration. I have no more fun when driving the car.

Before the car was concerning the engine was for me completely vibration free. OK, some light shaking in the seat when standing at the traffic lights, but no engine related vibrations above idle. So i'm a kind of desperate at the moment.

Rotate the front tires side to side to see if the vibration follows to the other side, maybe the shop bent a wheel while test driving.

[Starter986]

Have you considered, and I'm thinking outside the box here, that maybe you've, under the circumstances you describe, have going on a perfect trifecta of vibrations from a few parts/components that is causing a resonance?

[Smallblock454]

Originally Posted by BYprodriver

Rotate the front tires side to side to see if the vibration follows to the other side, maybe the shop bent a wheel while test driving.

Unfortunately it's not tyre related. Additionally all 4 wheels / tyres were rebalanced by the workshop. If i press the clutch and the rpms fall down, the vibrations go away immediately. Definitely engine related.

Originally Posted by Starter986

Have you considered, and I'm thinking outside the box here, that maybe you've, under the circumstances you describe, have going on a perfect trifecta of vibrations from a few parts/components that is causing a resonance?

Yes, i've considered that. But in my little world a resonance would only happen in a very specific rpm range – let's say a range of 500 rpms. But in my case the vibrations start at 1.500 rpms, are really present from around 2.000 to above 4.000 rpms and than disappear above 4.500 rpms. Also it is possible that i can't feel them below 1.500 and above 4.500 rpms.

In my understanding a resonance would only happen in a very defined rpm range, like the exhaust resonance in these cars, which are always around 2.800-3.000 rpms.

And even if there are more than 2 components that resonate with each other, the rpm / vibration range shouldn't be that big and evenly.

I'm still not understanding what is going on there and why the workshop didn't focus on eleminating the definitely engine related vibrations in the footwell.

[Gilles]

Did the shop installed a new flywheel..?

If not, perhaps the new clutch disk and the flywheel should have been balanced together? This means you may have to remove the tranny again to get rid of the vibration..

[BYprodriver]

Originally Posted by Gilles

Did the shop installed a new flywheel..?

If not, perhaps the new clutch disk and the flywheel should have been balanced together? This means you may have to remove the tranny again to get rid of the vibration..

Yes the dual-mass flyweels are not balanced very well when made & it's difficult to balance them regardless.

[Gilles]

Originally Posted by BYprodriver

Yes the dual-mass flyweels are not balanced very well when made & it's difficult to balance them regardless.

Indeed, but I was talking about balancing the flywheel and the pressure plate as a unit..