-----Original Message----- From: CDR Repro CC [mailto:cdrrepro@iafrica.com] Sent: Thursday, January 31, 2002 10:37 PM To: 928 Subject: [928] Dragging brakes Hello all At the risk of showing my ignorance to the workings of my cars brakings system, I would like to ask for ideas as to my problem. My 83S (pre ABS) began making some strange squeaking noises at low speeds. The noise happenend even when the car was rolling on smooth surfaces and thus is not suspension movement. Around about the same time I began to notice an intermittent feeling that the car was slowing during gear changes away from the lights and that on hills it would no longer roll back when one released the brakes. The problem would be at its worst after having been on the highway and having got into town, stopping at traffic lights. Due to less than technical description the shop that was servicing my car did not seem to listen to my symptoms and simply went ahead with a normal inspection. At first they merely cleaned calipers. No change. My front & back brake rotors were both heavily worn, with the fronts way below minimum thickness. At first I had the discs skimmed to take off the lip, but this actually made things worse. The car would now intermitently begin to shake and vibrate excessively at speeds over 60 mph. Strangely it was often worst when first getting on to a highway or when pulling away from a toll booth. The bad shaking would last for about a mile and then go away again, only to return a few miles down the road. I was told that the discs had warped or that the runout was 'incorrect' when they were skimmed. This doesn't explain the symptoms above. An investigation of the joints on the steering rack then revealed excessive play. So we did a total overhaul on the steering rack and we replaced the front rotors (original factory part) & the brake pads (non-geniune) - costing me 3 months bond repayments on my 2 bedroom flat ! (due to SA foreign exchange rate) They also told me that the handbrake cable was badly stretched and had adjusted it, as I could not afford the ridiculous (more than a months bond repayment on my flat) cost of a new one. After adjusting the handbrake, the squeaking problem became far worse and so they backed off the adjustment. The squeaking has not returned since. Since having collected my car after the brake & steering overhauls I have covered only about 70 miles, mostly in town. It soon became apparent that the brakes were still prone to dragging intermittently. Yesterday I had the wheel alignment done (by a non-Porsche specialist, but who had specs for their system). I took the car out onto the highway yesterday afternoon and I am very disappointed. The car soon began its shaking and the brake drag became extreme. Pulling off and stopping sharply on the side of the highway doesn't require touching the brake pedal! A friend who was dribing behind could not see any wheels shaking but said that the brake lights would flicker on and off at the time I began to feel the shaking. Strangely the one thing that appears to give the system relief is a brief stint of reversing. I was hoping to take the car on a 2 hour trip this evening but it looks like I'll be in my old pickup truck. So, are all these problems related? Steering rack - wheel alignment - handbrake - brake system. Is the shudder related to steering and alignment, or it as a result of a brake problem? Is the handbrake a hydraulic system? Could this be faulty and be causing the other problems, including the flickering brake lights? Is it just chance the squeaking and the brake drag started at the same time? And the shuddering? Someone with more understanding can hopefully put the pieces of the puzzle together better than me. Peter 83S South Africa From: Jim Bailey [jim@928intl.com] Sent: Monday, February 04, 2002 1:08 PM To: 928 Subject: [928] RE: Dragging brakes The fact that your brake light switch is being engaged means that the brake fluid is under pressure . All 78-83 928s trigger the brake lights off the master cylinder . You have been driving around with all four calipers dragging wearing out the rotors and overheating warping them and wearing out the brake pads . It has nothing to do with the hand brake that is seperate mechanical system with independent shoes inside the rear rotor in a special drum . The obvious question is why are the brakes being pressurized all the time ? . The most likely occurance would be a failed brake booster which thinks you are pressing lightly on the pedal all the time . You can very carefully test this by disconnecting the vacuum line from the booster ( use extreme caution ) You could test drive in a safe location and see if the brakes begin to self apply with out the vacuum boost connected . BE VERY CAREFULL without power assist it is very hard to stop . Wally points are an excellent (as usual) indepth discussion of various tests but focus on the defective booster or lack of freeplay at the pedal . Jim Bailey 928 International Jim@928intl.com www.928intl.com (714)632-9288 From: Jay Kempf [mailto:jkempf@tds.net] Sent: Monday, August 05, 2002 5:25 PM To: 928 Subject: [928] RE: Brakes dragging? rebuild? >-----Original Message----- >From: Gary Tilson [mailto:gt225000@mindspring.com] >Sent: Monday, August 05, 2002 5:16 PM >To: 928 >Subject: [928] Brakes dragging? rebuild? > > >I have had an occasional problem with the brakes on my '89 S4 car >dragging. It's been slight and was at first hard to diagnose. There >wasn't any strong pull to one side or another so maybe both fronts >are occasionally dragging. It usually happens when they get hot. On >a 95 degree day they may start to drag after 20 minutes. When I pull >back into the garage, they are very hot. When this happened several >months ago, I bled the brakes and it seemed to take care of it for >awhile. I bled the brakes last week and no cigar; they began >dragging the next time out. I have been using Super Blue brake fluid. > >Has anyone had these symptoms, and if so what did they do to correct it? > >Should the calipers be rebuilt? How hard is it and are kits available? > >What about the master cylinder? rebuild? It does not leak externally. > >Any help would be greatly appreciated, I would like to remedy next >week at the latest. > >Thanks >-- >Gary Tilson >'89 S4 Guards Red Cool, an actual question. Let's work from the back of your list to the front. Master cylinder. Usually responsible for not applying the brakes when it fails so not a likely candidate for dragging them. However, one symptom is that the vacuum seals fail at the back and allow fluid to be sucked into the vacuum booster eventually dragging the brakes by hydrolock. A candidate if you are pouring in fluid and don't know where it is going. If it gets bad you will see puffs of some unknown smoke coming out of your tail pipe and that is the brake fluid getting sucked through the vacuum system. Calipers. They usually don't go all at once and/or aren't variable or moving around the car with random symptoms. Usually associated with a pull when one or more go out and the brake at that corner isn't working so the brakes would feel less effective and the steering wheel would respond so not likely either. Also, the 4 piston calipers are not easy to rebuild so you don't want it to be that. Not really hard just involved. The heat related part of the syndrome is telling a bit but may just be normal. Brake fluid expands when it gets hot if it has no where to go it will drag the brakes. The other thing that can be a factor is old rubber lines. They can collapse after time or the rubber liner layer can come loose and occlude the inside. But again that is normally one caliper not both fronts. But bleeding might dislodge something so it could be. My guess, if I have to guess is two fold. If you have been pouring in fluid and it isn't coming out on the ground or leaking anywhere you can see then you have a vacuum booster full of fluid. You can suck out the fluid through the vacuum connection and see if it makes a change. If you haven't been losing fluid I hate to even say it but your booster may have failed in the same way mine did and it is done. Needs replacement. Hope that helped. Jay K.