This is a 2010 Panamera with 14K miles. Car feels as if it is going over 3 or 4 little bumps -- it "hops" up -- after backing up maybe 10 or 15 feet on level, smooth surface (such out of the garage onto the driveway) in the morning when car is cold. Sound and vibration seems to come from the rear of the car. Never happens when car has been driven for a bit, but may recur after car has set for several hours. May also occur moving forward.

I suspect faulty rear brake cylinders.

Have it at the dealers right now. They say they have never heard of such a problem before.

 

Is it when you are turning or going in a straight line and is the air temperature cold ? if so it is the same issue described when turning a tight radius and the car makes that noise.

 

The "hop up" occurs when moving in a straight line. The car does not jerk to a stop, it feels as if the rear wheels just went over a speed bump while going 25mph, but I'm only going 5mph and the road surface is perfectly flat. It is unrelated to turning the wheel. And it can happen in average to warm temperatures, not just cold temps. It only seems to happen if the car has been sitting overnight in the garage or if the car has not been run for a few hours.

 

Not Normal. Rear pads locking? Hand brake off? Not a Car specialist, So just guessing.

 

Dealer was able to reproduce the problem I described in my first post in this topic. They said that they "re-torqued the rear suspension" and hope that will take care of this issue.

Then they said that in checking the records of the car they noticed that when I bought it, it had 19" wheels and before it was delivered to me they were replaced with 17" wheels (that was done at my request). They said the suspension should be aligned after changing the wheel size. I am skeptical, to say the least. They are implying that the need to align the suspension is related to the problem I am complaining about. I find this hard to believe.

Of course they want me to pay for the alignment, nearly $400. My opinion is that if it really is necessary to re-align the suspension after changing wheel size, that should have been done before I accepted delivery of the car and they should pay for it. They don't want to do that.

 

I suspect that doesnt cure it and the one who changed the 17 inch wheels before giving you the car is responsible for allignment payments as they failed to do so.

 

Kip, it was the Porsche dealer that changed the wheels from 19" to 17" before I took delivery of my new Panamera in 2010.

 

Tell them that the failure to adjust the chassis might have lead to unpredictable behavior of the car and this is something they should have done before delivery, so they are responsible for the bill. The customer can not know that any adjustments have to be made and they neglected to even mention it to you. Hope they fixed the problem and that it works out well for you, its the least they can do.

 

The dealer relented and did an alignment. Here are the key numbers from the report:

Rear axle camber:

Left before -1 degree 43' Left after -1 degree 30'
Right before -1 degree 38' Right after -1 degree 34'

Rear axle toe: essentially no change needed

Front axle camber:

Left before -0 degree 36' Left after -0 degree 29'

Right before -0 degree 22' Right after -0 degree 24'

Front axle toe:

Left before -1 degree 17' Left after -0 degree 08'

Right before -0 degree 01' Right after -0 degree 07'

Front axle caster: no change needed

The report also shows the spec values and +/- tolerance. The only specs that were out of tolerance were the front axle toe values, and not by much: a maximum of 6 minutes of a degree in the front axle toe. So I am skeptical that the problem I am experiencing is related to the suspension being out of alignment.

And my skepticism has been confirmed. Yesterday when I moved forward from a parking space that I had previously backed into an hour earlier that morning, the car "hopped" four times, then two more times in the first about 20 feet as I gently turned to the left at slow speed. This morning there was no "hopping" when backing out of the garage or moving away from a parking place an hour later.

So to sum up, all the dealer did was do some mysterious rear suspension adjustments (details unknown to me) and an alignment as described above. The problem re-occurred after those things were done.

 

Just as I expected, sadly. Do You have pdcc? That adjusts My Car in wierd places, but its not a hip, more like a lift. Still think that only thing able to hop a car up on a level surface are the brakes. One pad locking up? Try standing outside while someone else backs up to see if any visi le event.

 

Car does not have adaptive air suspension or PASM. Have had a friend watch as I started up but of course then it didn't do it.

Agreed, brake problem seems likely.

 

Latest update: yesterday the car did one quick "hop" up as I was pulling straight out of a parking space.

I am beginning to wonder if it "hops" because the ABS is being briefly activated, obviously inappropriately. To be clear, the "hop" does not occur when I am applying the brakes, it only occurs at very low speeds when the car has been sitting for at least an hour. But a brief ABS activation might result in the car suddenly jumping up, as if it had hit a small speed bump.

So just to test if the ABS was working correctly, I found a deserted street and at 40mph hit the brakes as hard as I could. I could feel the ABS come on and the car stopped quickly and smoothly. Felt normal to me. Now lets see if I get more "hops".

 

The car continues to "hop" every few days, usually just one small hop at slow speed on level ground when leaving a parking space. Note: I do not use the E brake when parking on level ground.

Interestingly, the other day it did a series of 3 to 5 quick "hops" twice within 5 seconds, again while moving slowly while going forward leaving a parking space.

I am going to take it to another Porsche dealer as soon as they let me know they have a loaner car for me.

 

Car is still doing it. Taking it in to the dealer again today. Different dealer than I mentioned earlier.

 

Rear differential limited slip is binding. Pretty sure the diff lock is electric on these cars. Although I assume it could possibly be mechanical too.

If nothing is found, I would replace the rear differential fluid and be sure to add any needed additives. I would think there would be an issue at parking lot turn speeds too, but possibly not.

My other theory is clutch related, since the PDK slips the clutch in reverse. However, the rear would only feel it due to driveline transfer.

Good luck, and report back.

Mike.