When I brought my 928 for a service inspection, the Porsche mechanic told me the callipers of the brakes were all stuck. This wasn’t to big of a problem, but the braking capacity is much smaller he said. Can someone tell me of this is true and if it is advisable to have them done? I know the best thing would be getting everything to normal, but I had a lot of expenses lately (T-belt, servicing, waterpump, new paint, etc.) . So I like to postpone this for a while.

Doe the car brake better when the callipers are OK? Can I get them loose myself easily?

 

What does "stuck" mean? if the pistons are siezed, you would cook the rotors, and burn up the pads, the car would run very badly. The brakes will have to be rebuilt. If "stuck" means the caliper blocks are froen on their mounts (unlikely) then you will have slightly less severe but similar problems, but one side of the brakes will wear faster than the other. This is something you can easily check out yourself. Take the wheels off, disassemble the caliper blocks from the mounts, lubricate (see manual) and reinstall. Should take an hour or so in a reaonably well equiped shop.

 

An old friend of mine once said-
Brakes and Steering laddy, you can walk away from anything else.
Never mess with these two things. If the brakes have a problem, they should be serviced to function at factory specifications.

Cheers

 

I would want a second opinion ASAP from someone who is familiar with brakes.

The problem is in finding someone that you can trust. I am sorry to say that I believe that if you take the car to virtually any of the franchise brake or tire operations, you will be told that you have a problem, whether there is a problem or not.

I suggest that you try to find an independent shop that some of your friends or coworkers trust, and let them look at the brakes. It would be better if it were a Porsche shop, but the brake system is nothing exotic, and any good shop should be able to check them.


If you give your location, someone here might know of a shop in the area.

 

Well, first of all, does the car stop?

If not, you've got a problem. Take it to a shop, or disasymbole everything, and fix it. Who knows what it could be. Master cylinder, pinched lines, bad calipers?

I would assume the car stops.

Find a decent slope. Put the car in neutral, and let off the brakes. There should be a moments hesatation, and then it should begin to roll. the moments hesitation would be the time needed for the calipers to retract when your motionless. When your moveing there is always a small amount of run out in your rotors, pushing the calipers back for just about instant responce. If the car doesn't roll, you probably have a stuck caliper.

Since the car stops, the calipers shouldn't be stuck open. Lift each of the tires off the ground. If you can turn the wheel with your hands it's probably not stuck. If you can't turn the wheel, or it's very difficult, you probably have a stuck caliper.

After finding the wheel(s) that have problems, take the caliper(s) apart. Check the seals. Greese the pistons up, rough up the pads with a bit of sand paper, and put them back together, put them back on. Bleed the brakes. Try to avoid getting greese on the rotors or pads. You might want to put dampanders on them if they're not already. You also might concider putting a angle on the frount of the pad to stop squeeking.

My 83 had a sticking caliper. The caliper is made of steel, and rusted enough to put a bind on things. I cleaned the rust up, greesed the pistion, and put it all back together. I had troubles with the reassymbly. It take a bit to get the hang of it.

If you do have a stuck caliper, the rotors and pads will wear excesivly, and be very hot all the time. When you go through a large water puddle, the rotors can worp. This is what mine did. Also if you have a manual car, you'll be amazed at how much easyer launching is.

 

[quote]Originally posted by ViribusUnits:
<strong>&lt;&lt;snipped&gt;&gt;
After finding the wheel(s) that have problems, take the caliper(s) apart. Check the seals. Greese the pistons up, rough up the pads with a bit of sand paper, and put them back together, put them back on. Bleed the brakes. Try to avoid getting greese on the rotors or pads. You might want to put dampanders on them if they're not already. You also might concider putting a angle on the frount of the pad to stop squeeking.
&lt;&lt; snipped the rest &gt;&gt;</strong><hr></blockquote>

The S4 has aluminum calipers, rather than the steel that the writer's '83 car has. The calipers are two-piece assemblies that should not be disassembled unless there is a leak. The pistons can be removed for inspection one by one without splitting the caliper castings.

DO NOT USE GREASE on any hydraulic brake parts, ever. The caliper bores and the OD of the pistons can be lubed with a brake assembly lube if you feel it necessary, but first the parts need to work freely without any lubrication. For most of us a little brake fluid to ease the insertion og the piston seal is all it takes.


The only reason that S4 and later calipers stick is because the fluid is contaminated. Moisture causes corrosion, but frankly there is a much bigger chance of seeing steel master cylinder problems than corrosion in the aluminum calipers. If you keep the fluid flushed per Porsche recommendations (every two years) you will likely never see any corrosion or crud in the hydraulics.

Sticking calipers always stick in the 'engaged' positions, causing excessive drag, rotor heating from friction on the dragging pads, and therefore a risk of pre-faded brakes and warping of the rotors as they heat and cool unevenly. Quick-and-dirty test: raise each corner of the car using the jack, and turn each wheel by hand. Brakes are off, car in neutral. You'll know quickly if the brakes are dragging, since turning that wheel will be really hard, and you'll hear the pads dragging.

 

As always, excellent advice from dr. bob!

I would like to add one bit to his advice.

A sticking caliper is not the only thing that can cause the brakes to drag and overheat - rubber brake lines can swell and make very effective check valves. The XJS had a single rubber line to the inboard rear calipers. The brakes started dragging while I was twenty miles from home - after five minutes of driving, they were cherry red! I loosened one bleed screw just a tiny bit - this would leak enough to bleed off the pressure so I could drive the car, but not enough to keep the brakes from working.

 

Just a question.

What would greese do to the hydrolic parts?

I never realy pay much attention. I ask my neibor/parts house what I need, he hands me a jar to barrow/buy and I go at it. One more trusting fool.

Thanks

 

[quote]Originally posted by ViribusUnits:
<strong>Just a question.

What would greese do to the hydrolic parts?

I never realy pay much attention. I ask my neibor/parts house what I need, he hands me a jar to barrow/buy and I go at it. One more trusting fool.

Thanks</strong><hr></blockquote>


Depending on what you apply and where you apply it, grease will often soften and swell some rubber parts in your system. Note that the warning applies to the hydraulic parts. Metal-to-metal caliper slides on some cars, for instance, need a good chassis lube where the sliding takes place.

 

Thanks for all the suggestions. The car is still able to firmly press my nose against the windshield. I'm not sure how a car without this problem would brake. The wheels can turn freely. First thing monday morning is call the Porsche mechanic. Just for the record, I took the car to an official Porsche dealer/service station. They should know as well as any I must assume. The report they gave me says: "remtangen reviseren". Now that may sound pretty Dutch to you. I don't know the correct translation for that, but it's something like "revising the brakeconstruction (tang means something like twister, pliers, or squeezer. I’ll try to look it up).