Hill holder issue
11-24-2018, 08:39 PM
#1
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Hill holder issue
I've noticed lately ( after being held on a hill by the hill holder) that when I drive off that there is a rattling/ thumping sound coming from the rear of the car. It's only momentary and not always. Wonder if it has something to do with the braking system? I couldn't of a proper search title. Any help out there? Oh yea were talking a 2012.5 CS PDK.
11-24-2018, 08:59 PM
#2
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Mileage?
Probably need new brake pads. Check your pads. And rotors for wear.
Probably need new brake pads. Check your pads. And rotors for wear.
11-29-2018, 05:54 PM
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Did you change the PDK parking brake pad too?
11-29-2018, 08:44 PM
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https://www.sunsetporscheparts.com/a...omponents-scat
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11-30-2018, 09:40 AM
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Are you sure? I don't think this is right.
Also, on my manual trans, there is a slight clunk when hill hold releases. It's normal. It's the same as when you don't manually release the e-brake, and just use the car's momentum.
Also, on my manual trans, there is a slight clunk when hill hold releases. It's normal. It's the same as when you don't manually release the e-brake, and just use the car's momentum.
11-30-2018, 09:53 AM
#10
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It is using brakes like LexVan says. From Porsche literature for the 991 models:
"The new standstill management function (Auto-hold function) prevents the vehicle from rolling back in the opposite direction to the desired driving direction. If the vehicle is braked to a stop on a gradient, the Auto-hold function is active and the required brake pressure is maintained via PSM. On vehicles with PDK, the Auto-hold function also holds the vehicle if the driver allows the vehicle to coast to a stop on a. gradient. As soon as the vehicle comes to a stop without braking, the brake pressure is maintained via PSM for holding the vehicle on the gradient until it moves off again. The hold function is transferred to the electric parking brake after 5 minutes or if the system detects that the driver intends to leave the vehicle."
"The new standstill management function (Auto-hold function) prevents the vehicle from rolling back in the opposite direction to the desired driving direction. If the vehicle is braked to a stop on a gradient, the Auto-hold function is active and the required brake pressure is maintained via PSM. On vehicles with PDK, the Auto-hold function also holds the vehicle if the driver allows the vehicle to coast to a stop on a. gradient. As soon as the vehicle comes to a stop without braking, the brake pressure is maintained via PSM for holding the vehicle on the gradient until it moves off again. The hold function is transferred to the electric parking brake after 5 minutes or if the system detects that the driver intends to leave the vehicle."
11-30-2018, 10:12 AM
#11
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Here's what I'm thinking about OP's problem.
When hill-hold is used, the brakes are being applied to keep the car from rolling backwards, so in effect they are being applied in a direction opposite to the forward rolling direction of the car. There is a small amount of lateral play in pads as they sit in the caliper in the rotational director of the rotor (lateral as viewed when looking at the pads from the flat side of the rotor), or else they would be rigidly held and would stick. This play is normally very small though. You can typically feel this play when you install your own pads. So as the weight of the car rolls back as the hill-hold takes effect, the pads will shift slightly back in the calipers to the same position they would sit in if the car was being braked while moving in reverse.
So when a car using hill-hold starts to moves forward under power, for the brief moment before the hill-hold function releases the brakes the pads would move back to the other end of their travel in the caliper just as if you where braking the car in a forward direction.
Maybe the new pads fit a little more loosely than the original ones and have more lateral play in the caliper. The thump/rattle could be the sound of the pads shifting to their forward movement position in the caliper as launch occurs and hill hold releases. If the pads are not OEM, then additional play is possibly even more likely.
When hill-hold is used, the brakes are being applied to keep the car from rolling backwards, so in effect they are being applied in a direction opposite to the forward rolling direction of the car. There is a small amount of lateral play in pads as they sit in the caliper in the rotational director of the rotor (lateral as viewed when looking at the pads from the flat side of the rotor), or else they would be rigidly held and would stick. This play is normally very small though. You can typically feel this play when you install your own pads. So as the weight of the car rolls back as the hill-hold takes effect, the pads will shift slightly back in the calipers to the same position they would sit in if the car was being braked while moving in reverse.
So when a car using hill-hold starts to moves forward under power, for the brief moment before the hill-hold function releases the brakes the pads would move back to the other end of their travel in the caliper just as if you where braking the car in a forward direction.
Maybe the new pads fit a little more loosely than the original ones and have more lateral play in the caliper. The thump/rattle could be the sound of the pads shifting to their forward movement position in the caliper as launch occurs and hill hold releases. If the pads are not OEM, then additional play is possibly even more likely.
11-30-2018, 10:18 AM
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Here's what I'm thinking about OP's problem.
When hill-hold is used, the brakes are being applied to keep the car from rolling backwards, so in effect they are being applied in a direction opposite to the forward rolling direction of the car. There is a small amount of lateral play in pads as they sit in the caliper in the rotational director of the rotor (lateral as viewed when looking at the pads from the flat side of the rotor), or else they would be rigidly held and would stick. This play is normally very small though. You can typically feel this play when you install your own pads. So as the weight of the car rolls back as the hill-hold takes effect, the pads will shift slightly back in the calipers to the same position they would sit in if the car was being braked while moving in reverse.
So when a car using hill-hold starts to moves forward under power, for the brief moment before the hill-hold function releases the brakes the pads would move back to the other end of their travel in the caliper just as if you where braking the car in a forward direction.
Maybe the new pads fit a little more loosely than the original ones and have more lateral play in the caliper. The thump/rattle could be the sound of the pads shifting to their forward movement position in the caliper as launch occurs and hill hold releases. If the pads are not OEM, then additional play is possibly even more likely.
When hill-hold is used, the brakes are being applied to keep the car from rolling backwards, so in effect they are being applied in a direction opposite to the forward rolling direction of the car. There is a small amount of lateral play in pads as they sit in the caliper in the rotational director of the rotor (lateral as viewed when looking at the pads from the flat side of the rotor), or else they would be rigidly held and would stick. This play is normally very small though. You can typically feel this play when you install your own pads. So as the weight of the car rolls back as the hill-hold takes effect, the pads will shift slightly back in the calipers to the same position they would sit in if the car was being braked while moving in reverse.
So when a car using hill-hold starts to moves forward under power, for the brief moment before the hill-hold function releases the brakes the pads would move back to the other end of their travel in the caliper just as if you where braking the car in a forward direction.
Maybe the new pads fit a little more loosely than the original ones and have more lateral play in the caliper. The thump/rattle could be the sound of the pads shifting to their forward movement position in the caliper as launch occurs and hill hold releases. If the pads are not OEM, then additional play is possibly even more likely.
11-30-2018, 06:07 PM
#13
Without question, I can see the benefits of Hill Hold on a three pedal manual car; but, why in the world do you need the Hill Hold function on a two pedal PDK car?
11-30-2018, 06:14 PM
#14
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Thanks for all the good replies. So my final question-- is the "hill holder" function a part of the transmission (in my case PDK) OR is it part of the braking system? If the latter is true then I probably should remove the rear rotors and double check the parking brake hardware.
11-30-2018, 06:16 PM
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Thanks for all the good replies. So my final question-- is the "hill holder" function a part of the transmission (in my case PDK) OR is it part of the braking system? If the latter is true then I probably should remove the rear rotors and double check the parking brake hardware.