Nicholbry

I've done some searching and uncovered various threads related to answering specific questions regarding brake caliper rebuilds. For some, the question relates to making sense of parts supplied in rebuild kits that don't seem to match up to the original equipment or their specific model year. Others, answer questions about piston dimensions, caliper painting, etc.

Perhaps it's here somewhere, but I could not find a step-by-step tutorial (with helpful pics) on rebuilding the brake calipers on our cars. Specifically, my car, which is a 1990 S4. My rear brakes sound as though they are not disengaging completely from the rotor. Given the previous owner's disregard to maintenance, I'm figuring a rebuild is in order. Besides, it's been almost 19 years anyway.

I found a website that shows a Willwood disassembly/rebuild. Although it was helpful, I was hoping someone had posted a thread specific to our caliper design. Has it been documented here before and I was just unable to locate it? Us Rennlisters seem to have the most comprehensive how-to guides (timing belt, engine removal, torque tube replacement, etc.) of any other forum I've visited, so I assumed it would be out there somewhere.

I'll likely start with the rear as they are barking the loudest at the moment.

Thanks for any help you can be.

Kindest regards,
Nicholas

Lizard928

Rebuilding calipers is very easy.

take a 2x4 and cut it to size so that it will fit in the caliper, then take compressed air and give small bursts of air to push the pistons out.
I have yet to see one of these calipers really gummed up, but if you have a piston or two which isnt coming out, try to force the piston back into the caliper and try again. This may take a few attempts but should work.
If it doesnt work right away and you get abit over zealous with the air pressure KEEP your fingers OUT from around the pistons. If it comes free in a hurry the piston can VERY EASILY remove a finger, I have personally seen it happen.

Once the piston is out remove the old seals/dust boots. Proceed to clean out all old fluid with any sort of a solvent, but dont leave it in there long as the caliper is aluminum. Once clean move onto the pistons. Make sure you clean all these parts to remove all your cleaning agent.

If they were diffucult coming out take extra time to inspect them, make sure that they are round, not warped, or damaged in any way. Once done install the fresh seals into the caliper and reinstall pistons, Possibly use alittle brake fluid on the seals to lube them for install. Once they are in, install the dust boot, and you are done.

Nicole

We did this on my car in Fall, including front and rear calipers, flex brake lines, and master cylinder. The trouble is that even after 10 times of bleeding the system, the pedal feel is still soft, and there is no strong pressure point as there was before. I have to press the pedal about 1-2: further for the same brake performance. It feels like I'm hitting a sponge.

I'm at the end of my whit. Bill and Christoph as well as a few other local 928 owners have tried to help. The Porsche dealer couldn't figure it out, either.

If I knew what went wrong, I could advise you what to avoid. I hope you won't run into this issue.

GregBBRD

Nicholas:

Be careful here. Price out the caliper kits and new calipers first. Most of the time, new calipers are a really good deal, from Porsche, when compared to the repair kits.

jon928se

Caliper seals changed in '89 so your '90 should have the later seals and pistons which are a protective cap rather than a scraper ring. But it would be wise to check the actual seals that are fitted before purchasing - it wouldn't be unheard of for "old" style seals and pistons to have been used on a later car.

I was going to upload the relevant bit of the WSM describing the change (not that it helps a lot) but I B seems to have lost it's member list ....
Could not find file 'C:\Mall\docs\chat\fpdb\members.mdb'

Nicole

New front calipers for the S4 models are more than a pair of GTS calipers. If you go the new parts route, you may as well upgrade to GTS brakes.

ROG100

Greg is right on the money - I get asked a lot for caliper reseal kits for the 87 to 95 cars.
A seal kit is circa $45 to $60 per piston. Thats something like $200 per caliper.
I have only been able to get the kits from Porsche so hence the price.
Other suppliers who claim to have the right parts do not.

New GTS calipers are $428 each. S4 are $560 each.

Vlocity

Nicole,

One additional step that I take about once a year is to loosen the caliper (on the rears I loosen one bolt and remove the other) so that the orientation of the bleeder is truly at the top of the caliper and do a final bleeding of the brakes. I always get a few extra bubbles of air when I take the time to do this.

Good Luck.

Ken

SeanR

How much does 928 Int charge for used calipers? Anyone know right off hand?

StratfordShark

$400 for a pair of used front calipers, $550 each brand new.

That's before the 50% used sale discount...

mark kibort

How do you know that the rear are not disengaging? drive down the road first thing in the morning and pull over after not using the brakes and see if the rotors are warm. could be a dragging parking brake if you are hearing rubbing sounds. Its very unlikely the calipers need rebuilding. these are brembos and rarely have issues on street cars. usually, its the master cylinder if the system is dirty and has been neglected. what do the rotors in the rear look like? grooved? worn with an edge ridge? you can check the calipers by pushing one piston in the caliper and watching the other pop out smoothly, or press the entire pad to push both pistons back in the caliper while watching the other side of the calipers pistons pop out. If things are smooth, the calipers are probably fine. I would just flush the system real good and see if things change first.

mk

Dwayne

Hello Nicholas,
I'm planning on rebuilding the calipers on the '87 S4 next month and will be documenting the process in detail with pics. Right now, I'm wrapping up the engine refresh on the same car (hopefully I'll be able to fire it up today) and plan to post pics of the process first. Then on to the Brake rebuild - probably won't get pics and documentation of the brake rebuild posted until the end of January, though - if you're not in a hurry.

Glen McCartney

Went looking through my archives, remembering there was a place to buy the seals and dust boot cheaply. You have to remove the pistons to measure them for the correct size seals. I haven't had the need yet. The price is $25/kit. Each kit includes two dust boots and two pressure seals. Order one kit per 2-piston caliper, two kits per 4-piston caliper. If you order from them, let us know how they work out.

Here is link:
http://www.zeckhausen.com/Brembo/Con...es.htm#Rebuild

ROG100

Hi Glen,
I ordered them from zeckhausen and they were the wrong size. When you order they will tell you that they do not guarantee the fit.
Price was right but not if they won't work.
I have a box full of there seals and boots if anyone wants to try them.
Maybe we can find out what fits and what does not and come up with a compromize of some sort.
Roger

Glen McCartney

Roger good info, I wasn't sure if what they offered would work on our calipers. It seems like they offer all the sizes of the different pistons in the various calipers in the 928. Like you said, good prices, but not if they don't work!

Thanks