brakes broken?
11-07-2016, 03:04 PM
#1
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Thread Starter
brakes broken?
Got a new to me 2005 Turbo.
The brakes were wonky when I got it. They kind of worked for light braking but the pedal was really hard if you wanted to stop faster or as you are just came to a stop. You had to pay attention at stop lights keeping your foot hard on the pedal or it would start creeping.
Checked the brakes and found someone had put 320mm rotors on instead of the 350mm rotors on the front and only half the pad were touching the rotors. Changed out the rotors and put new pads on. Didn't feel much better though.
Within a day of driving the brake booster light came on. The line to the booster was leaking. Replaced it.
Still same hard pedal and no hard braking. No booster light. Replaced booster and master cylinder. Much better, not so much the hard pedal, and brakes better, but still seems to take a LOT of pedal pressure to evoke ABS. If you really stomp it the ABS will come on. It didn't before replacing booster. It's like the last half of the pedal travel isn't adding very much more braking.
The main thing I really notice is when you lift off the brakes just as you stop the front end doesn't lift at all. It's like the front brakes aren't working hard enough to transfer weight to the front and compress the front springs when stopping.
Had it checked out at Porsche mechanic and tells me I just need to bed in the new pads and rotors. That doesn't seem right to me. I've replaced rotors and pads, even went to racing pads on some cars and never had this.
Did the wrong size rotors mess up the front calipers and I need to replace them?
The brakes were wonky when I got it. They kind of worked for light braking but the pedal was really hard if you wanted to stop faster or as you are just came to a stop. You had to pay attention at stop lights keeping your foot hard on the pedal or it would start creeping.
Checked the brakes and found someone had put 320mm rotors on instead of the 350mm rotors on the front and only half the pad were touching the rotors. Changed out the rotors and put new pads on. Didn't feel much better though.
Within a day of driving the brake booster light came on. The line to the booster was leaking. Replaced it.
Still same hard pedal and no hard braking. No booster light. Replaced booster and master cylinder. Much better, not so much the hard pedal, and brakes better, but still seems to take a LOT of pedal pressure to evoke ABS. If you really stomp it the ABS will come on. It didn't before replacing booster. It's like the last half of the pedal travel isn't adding very much more braking.
The main thing I really notice is when you lift off the brakes just as you stop the front end doesn't lift at all. It's like the front brakes aren't working hard enough to transfer weight to the front and compress the front springs when stopping.
Had it checked out at Porsche mechanic and tells me I just need to bed in the new pads and rotors. That doesn't seem right to me. I've replaced rotors and pads, even went to racing pads on some cars and never had this.
Did the wrong size rotors mess up the front calipers and I need to replace them?
11-07-2016, 03:43 PM
#2
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As the mechanic told you - the new pads will not work all that well until the pads are mated to the rotors (bedded in..) That's done by using the brakes. To make it happen a bit faster - find a road where you can do repeated runs up to around 60MPH, then full-on (almost to ABS) braking down to 5MPH and repeat. You'll feel the mating going on as pad material is transferred to the rotor and braking becomes much more effective. And the front end doesn't dive on a Cayenne under braking - that's lesser cars that do that. I'd assume you have air-suspension since it's a turbo and that resists dive under braking.
11-07-2016, 08:12 PM
#4
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Then the front will probably dive on your turbo once you break the pads/rotors in. If you check the manufacturer's info - they'll likely tell you 100-200 miles are required to achieve full braking capability.
11-07-2016, 11:12 PM
#5
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As the mechanic told you - the new pads will not work all that well until the pads are mated to the rotors (bedded in..) That's done by using the brakes. To make it happen a bit faster - find a road where you can do repeated runs up to around 60MPH, then full-on (almost to ABS) braking down to 5MPH and repeat. You'll feel the mating going on as pad material is transferred to the rotor and braking becomes much more effective. And the front end doesn't dive on a Cayenne under braking - that's lesser cars that do that. I'd assume you have air-suspension since it's a turbo and that resists dive under braking.
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11-09-2016, 02:55 PM
#8
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Thread Starter
Reliable independent shop did it and said everything looked when replacing the smaller rotors.
Replaced booster and master after the booster line and proper rotors and pads did not fix it.
Replaced booster and master after the booster line and proper rotors and pads did not fix it.
11-09-2016, 08:02 PM
#9
Did your mechanic activate and bleed the abs pump with a diagnostic tool? Replacing the master requires careful bleeding and installation. I wouldnt trust a pressure bleed for a master, I always do mine on the bench manually.
11-10-2016, 08:12 AM
#10
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Thread Starter
They always follow the factory procedures.
The actually told me to drive it to get the pads seated in to see how it goes.
Just drives me crazy when I can tell when something isn't right.
Seems like I hear the brake pump running quite often. Like almost every time I use the brakes. Vacuum leak?
Replaced the battery yesterday. Started throwing a failure codes like 4 wheel drive system failure.
Load tested the battery and it was dropping to 6 volts. New battery and a reset and no more codes.
Have had to do a lot of neglected and poorly done maintenance repairs, but got it really cheap and haven't quite reached the market value yet.
Tell myself that since I am having to go thru it, it will be a little longer before those systems need attention again. Almost like new right?
The actually told me to drive it to get the pads seated in to see how it goes.
Just drives me crazy when I can tell when something isn't right.
Seems like I hear the brake pump running quite often. Like almost every time I use the brakes. Vacuum leak?
Replaced the battery yesterday. Started throwing a failure codes like 4 wheel drive system failure.
Load tested the battery and it was dropping to 6 volts. New battery and a reset and no more codes.
Have had to do a lot of neglected and poorly done maintenance repairs, but got it really cheap and haven't quite reached the market value yet.
Tell myself that since I am having to go thru it, it will be a little longer before those systems need attention again. Almost like new right?
Last edited by RKD in OKC; 11-10-2016 at 08:35 AM.
11-10-2016, 08:40 AM
#11
Rennlist Member
Have they measured the vacuum at the pump? The 4.8L engine uses an engine driven pump, sounds like 4.4L could be electric.
The 4.8L measures about 20" of mercury with a fresh pump. I know that because I replaced my pump at 60K mi.
Using the vacuum gauge you could pinch off the vac line near the pump to determine if its weak or if there is a leak.
The 4.8L measures about 20" of mercury with a fresh pump. I know that because I replaced my pump at 60K mi.
Using the vacuum gauge you could pinch off the vac line near the pump to determine if its weak or if there is a leak.
Last edited by v10rick; 11-11-2016 at 07:32 AM.