hey guys

have an 08 cayenne turbo

at a stop, when you put it in drive, it does not roll forward

e-brake is not applied

any ideas what this may be?

thanks

 

Can you clarify what does "not roll forward" mean? Are you talking about "brake rolling" or it does not move when you press on the accelerator?

 

like when you put it in drive and let off the brake, its supposed to accelerate on its own power and coast at 5mph...isnt it?

it moves when u press on the accelerator

 

Shift it into 1st and see if it moves on its own.

 

Not necessarily.. not sure if I am seeing an issue here. It certainly can roll, not too sure if I would say it "should" roll. There are more factors at play than you may be considering.

 

tried that last night, no change

 

i'd like to think that there isnt an issue here

its just i kind of expected it to roll? maybe its too heavy of a vehicle and it wont?

but the only cars that i have had that dont roll are BMW's with SMG/DCT trannies

 

Well, they are equipped with "hill hold" a feature designed to make it stay in place.

 

Are you having any issues with the vehicle??? If not, why not drive the C and enjoy. The next service you have it at the dealership have them do a full check up and report.

 

IMO, it may be the case of the hill roll feature being mis-set.

When you have an automatic transmission auto (such as Cayenne here), and you place car into D gear, the auto transmission is engaged to drive (the clutch helps in transfer of the force to the wheels), so the car creeps forward. In manual transmissions, the left foot disengages the clutch while in drive (at a stop light), thus removing force transfer from wheels (and no creep).

So all auto transmissions will do this when on flat ground.

The Cayenne also has a feature which prevents the car from rolling back when stopped on a hill. If you ever had a stick shift and happen to stop on an incline, you know exactly what I mean. In the auto trannie car, when stopped in D mode on a hill, the car may begin to roll back slightly, so this feature is useful (I use it myself whenever opportunity knocks).

It is possible, that for some reason, the hill roll back feature is not set properly (too tight), being activated way too early, causing stopping even if car is on flat ground. I assume this would cause fast wear and tear on all brake components (and should be checked/adjusted asap - brakes are not cheap in Cayennes).

Another possibility is that the car brake system has a bind somewhere (in calipers, etc.) to cause the car to not roll freely.

The caliper pistons is what applies pressure to the pads, which transfer the force to rotor, slowing the car down. The pressure applied to pistons comes from the hydraulic system in the car. So you put your foot down on brake, it creates hydraulic pressure in the lines, forcing brake fluid to extend the brake pistons to increase traction between pad and rotor. In failing brake pistons, when you lift your foot off the brake, the piston does not have free play, and does not retract easily back into the caliper housing (often only partially). Again, this created heat/wear/tear on brake system.

I would inspect each caliper for signs of wear/tear. Look at pads and calipers. After you drive around the neighborhood without using brakes much, the rotors should be warm but not scorching hot. So if you drive around with keeping brake usage to minimum, park and spit at the rotor you inspect (OK - spray a bit of water on it - since you carry a portable water spray...lol).
If the rotor is really really hot, you will hear water evaporating, which means the rotor is getting very heated, meaning that caliper is binding in some way.
Under normal driving without much use of brakes, the water would not be evaporating right away. DO NOT TRY TO TOUCH ROTORS WITH FINGERS!!! - ask my how I know from when I was a kid - LMFAO - years after though.

 

[QUOTE=ciaka;3979630] When you have an automatic transmission auto (such as Cayenne here), and you place car into D gear, the auto transmission is engaged to drive (the clutch helps in transfer of the force to the wheels), so the car creeps forward. In manual transmissions, the left foot disengages the clutch while in drive (at a stop light), thus removing force transfer from wheels.......

Is that how that works... Really??

 

Denversteve, if you think I am wrong, please correct me so that I can learn from you, otherwise stop wasting everyones' time being a web drut.
...skipped over a lot of stuff ...torque conversion, gearing, etc, but at end of day the result is that.

Since your ridiculing statement implies you are an expert on automatic transmissions, please, please teach us all how it works and how it answers the question in this thread. If not, I would appreciate you keep quiet.

 

Sensitive are we? No. You pretty much have it covered.... Put it in D and drive.

 

...yep, that's the kind of guy I am - sensitive.

 

Ciaka, please refrain from immature name-calling. That is not the type of forum environment we want to promote.

Thank you.