'86ROW Brake lock ups
04-18-2012, 10:43 PM
#16
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Your right Leon. Thinking about this, the other thing that happens when the ignition goes off is the vacuum is lost. Could the brake booster be doing this somehow?
02-07-2013, 11:43 PM
#17
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I've just replaced the brake booster with a new one, thanks Roger.
What a bastard of a job. Fritz has a 10" booster and a 9" hole to get it through.
The washer pump has to be moved, that in its self isn't much fun.
Anyway, it's done and I'm just waiting for the master cylinder to come back from the brake specialist to see if was all worth it. A 500km trip up country and back should tell?
What a bastard of a job. Fritz has a 10" booster and a 9" hole to get it through.
The washer pump has to be moved, that in its self isn't much fun.
Anyway, it's done and I'm just waiting for the master cylinder to come back from the brake specialist to see if was all worth it. A 500km trip up country and back should tell?
04-18-2013, 11:45 PM
#18
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Fix this eventually by fitting a new power booster, thanks Roger.
Just did a 700km country trip brakes fine and no lock ups.
Just did a 700km country trip brakes fine and no lock ups.
When I adopted my '86 ROW 5.0L S, it had many issues but one still troubles me.
On long distance country trips only, the brakes will come on and stop the car, with a VERY hard pedal. It feels like the motor is dying but when I pull off the road and back off the throttle, it would stop dead.
I suspected the ABS because the ABS light would come on [correctly] with ignition and go off with crank [correctly] but come on as soon as the car moved off. Previous owner had taken it back to Porsche a couple of times but problem still existed.
Anyway, my mate and I just removed all disks, calipers, speed sensors and the ABS pump. I had the calipers o/h with genuine kits, including new pistons. We had previously checked the speed sensors, so we replaced all of them with a known good set. Then reassembled it all with a different ABS pump, all new hoses, pads, anti rattle plates and new front disks, flushed the whole system out with metho, then new fluid.
The brakes now feel even better than before and the ABS system behaves as it should. My wife and I just did a 5,200km test drive across the country [Australia] and the brake drag issue is still there! Not as severe as before, which just makes it harder to detect. They come on after maybe an hour or so of driving at speed but now not enough to stop the car, just get very hot and stink. In fact idling in drive, it still creeps along ok but with a very hard pedal.
Pumping the pedal will not release the pressure until the ignition is turned off. With the ignition off, maybe three pumps on the brake pedal and it's fine, start the car and away it goes with no issues for usually the rest of the day.
It has never done it around town, so I had this idea that using the brakes regularly would prevent the problem, so every few miles, I would press the pedal enough to just make the pads touch the disks. Sometimes I could feel a tighter pedal which would go back to normal free play after a couple of applications but it still beat me on all but one day out of 6 country driving days.
When the brakes do come on, they can only be released after the ignition is turned off, so there is an electrical function involved, which would seem to rule out mechanical issues.
The only thing left that I can think of is the ABS computer?
I would realy like some ideas, or even better, a solution to this problem.
Thanks in antisipation.
Mike
On long distance country trips only, the brakes will come on and stop the car, with a VERY hard pedal. It feels like the motor is dying but when I pull off the road and back off the throttle, it would stop dead.
I suspected the ABS because the ABS light would come on [correctly] with ignition and go off with crank [correctly] but come on as soon as the car moved off. Previous owner had taken it back to Porsche a couple of times but problem still existed.
Anyway, my mate and I just removed all disks, calipers, speed sensors and the ABS pump. I had the calipers o/h with genuine kits, including new pistons. We had previously checked the speed sensors, so we replaced all of them with a known good set. Then reassembled it all with a different ABS pump, all new hoses, pads, anti rattle plates and new front disks, flushed the whole system out with metho, then new fluid.
The brakes now feel even better than before and the ABS system behaves as it should. My wife and I just did a 5,200km test drive across the country [Australia] and the brake drag issue is still there! Not as severe as before, which just makes it harder to detect. They come on after maybe an hour or so of driving at speed but now not enough to stop the car, just get very hot and stink. In fact idling in drive, it still creeps along ok but with a very hard pedal.
Pumping the pedal will not release the pressure until the ignition is turned off. With the ignition off, maybe three pumps on the brake pedal and it's fine, start the car and away it goes with no issues for usually the rest of the day.
It has never done it around town, so I had this idea that using the brakes regularly would prevent the problem, so every few miles, I would press the pedal enough to just make the pads touch the disks. Sometimes I could feel a tighter pedal which would go back to normal free play after a couple of applications but it still beat me on all but one day out of 6 country driving days.
When the brakes do come on, they can only be released after the ignition is turned off, so there is an electrical function involved, which would seem to rule out mechanical issues.
The only thing left that I can think of is the ABS computer?
I would realy like some ideas, or even better, a solution to this problem.
Thanks in antisipation.
Mike