brisco

This is a 2010 Panamera with 14K miles. Car feels as if it is going over 3 or 4 little bumps -- the rear end "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 (but not just in cold air temps). 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. Not related to turning the wheel, happens when going in a straight line.

I suspect faulty rear brake cylinders.

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

ECS Tuning

That is weird, haven't heard of that issue before, keep us posted on what they find out.

brisco

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.

MJBird993

You should drive your car more.

If the service department is saying that you should have that done, then I would ask the sales department to pay half. You were the one that wanted the 17", so it really is all up to you, but if there truly is a difference is setup then they should have informed you of that at time of sale.

I doubt that they will, and I also doubt that this will fix the problem if it still occurs.

It is good though that they were able to replicate it and hopefully it has been fixed.

brisco

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.

rijowysock

wheel size has absolutely no affect on alignment.. think about it.. regardless of the wheel size.. the angle stays the same, 1 degree is the same with 14" wheels or 30" wheels.. sucks they charged you.. im not sure what it could be, car have air susp?

brisco

Car does not have adaptive air suspension or PASM.

disden

That sucks, hope things get worked out eventually. Why did you want 17's? Seem so small for this rather large vehicle, but I bet the ride is quite smooth/soft. Good luck.

brisco

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".

emayer

Curious problem. Given the slow speeds involved, I'm wondering if there is a fault with the e-brake or hill-hold function.

rijowysock

can you please elaborate the hopping?

can it be seen? videotaped?


maybe try disconnecting the negative terminal on battery or the ground cable under the driver seat for 5 mins and have the computer fully reset... if it's electronical glitch that will cure..

otherwise video taping would be appreciated.. not sure now exactly what u mean by a hop.

brisco

The problem occurs very intermittently. So far I have been able to have one person observe it while standing next to the car. A "hop" means the rear end jumps up, as if the rear end went over a speed bump at 25MPH, but this occurs on perfectly level surfaces (parking lots, city streets) at low speeds only, less than 10MPH.

keithos27

If it is ABS related as you think, do you see any lights come on on the dash when said hops occur?

rijowysock

i remember a friends bmw doing this in the past, no air susp.. nothing fancy, i honestly have no clue what is was.. sounds like the brakes are dragging and then letting go..

brisco

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.