S4 Front Caliper Rebuild Problem (pics)!
#16
Advanced
Thread Starter
Update - Front Caliper Rebuild
fraggle,
Pelican carries both old and new and in-between. They just have them listed incorrectly in their catalog. The correct kit is shown as an '88, 36mm and 44mm - around $100 per caliper. The Rock Auto deal is legitimate, but you send in your calipers for the rebuild...heck, I can rebuild 'em & price is about the same. You are correct however in that one cannot upgrade the existing caliper to the new style. I'm not going to worry about it, have sent back the old repair kits for credit & Pelican has sent me the correct ones. BTW, Bill was the only person out of 3 dealerships and 2 928 suppliers to correctly identify the mid-year caliper piston design change.That is awesome...thanks a million Bill!
Pelican carries both old and new and in-between. They just have them listed incorrectly in their catalog. The correct kit is shown as an '88, 36mm and 44mm - around $100 per caliper. The Rock Auto deal is legitimate, but you send in your calipers for the rebuild...heck, I can rebuild 'em & price is about the same. You are correct however in that one cannot upgrade the existing caliper to the new style. I'm not going to worry about it, have sent back the old repair kits for credit & Pelican has sent me the correct ones. BTW, Bill was the only person out of 3 dealerships and 2 928 suppliers to correctly identify the mid-year caliper piston design change.That is awesome...thanks a million Bill!
Ok, fraggle had it right. I installed what I had (big PIA getting the metal-ringed seal in the caliper BTW) in the left caliper, then cleaned & polished the tar out of the right caliper pistons. Cleaned up the seals with a little Brakleen on a rag & 600 sandpaper so all the residue was wiped away.
Voila! Brakes like a champ, no more pulling to one side, appears pads are wearing evenly again. I also replaced the front brake hoses with a set from Raybestos. Good quality stuff, made in America (unbelievable). I got to thinking that any OEM hose I purchased might just have been laying around & oxidizing for 18 years!
#17
Rennlist Member
Glad it all worked out. When I found the prices and requirements I went the cheap route. My rebuild was free because I didn't need to replace any parts. I was very careful & very lucky getting everything apart without damage.
When I tried to special order mine it ended up being NLA - it wasn't the piston size issue I ran into, it was the the dust covers problem.
When I tried to special order mine it ended up being NLA - it wasn't the piston size issue I ran into, it was the the dust covers problem.
#18
Drifting
Scraper Seals?
In this photo which I took in 2004 showing the how I failed to remove the domed machine screws, you can see that the scraper seals appear to be missing
Am I seeing that correctly?
They were like that when I bought the car almost 20 years ago, and I've not had any problems with the seals despite the abuse on track over the last 100k miles
Does this mean that I have 42mm & 36mm pistons, and the seal kits are NLA? (car is an early '87)
I don't fancy scrapping the calipers, as they are still working fine, so what about replacing the main seals, ignoring the scraper seals?
Last edited by UKKid35; 10-05-2020 at 08:09 AM.
#19
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I stock all the seal kits if you get stuck.
__________________
Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission? George Layton March 2014
928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission? George Layton March 2014
928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
#20
The scraper seals are located in grooves inside each piston bore and scrape brake fluid from the pistons whilst these are being pushed out when braking.
If you have had no leak then it means the scraper seals actually.. seal. You may want to add the missing outer seals to prevent dust from damaging the pistons and the scraper seals.
#21
Drifting
Thanks
What I can't work out is what type of dust seals should be present
Obviously I should just pull the pads, and pump out the pistons sufficiently to understand what I have
But I'd like to have the right parts ready if that's at all possible
What I can't work out is what type of dust seals should be present
Obviously I should just pull the pads, and pump out the pistons sufficiently to understand what I have
But I'd like to have the right parts ready if that's at all possible
#22
The main seals are like the ones on the left on that photo. The inner lip fits into the outer groove on the piston and the outer lip houses a steel ring that holds it in place on the caliper bore top, if that makes sense. The ones on the pictures are not exactly like the ones used on our calipers but you get the idea. The seals on the right are the scraper seals, with a square section. This is a warm topic to me as I have just prepped a set of big blacks for my 951.
PS: how are you doing with the Cerbera?
Last edited by Thom; 10-05-2020 at 05:02 PM.
#23
QUOTE=Thom;16946549]
The main seals are like the ones on the left on that photo. The inner lip fits into the outer groove on the piston and the outer lip houses a steel ring that holds it in place on the caliper bore top, if that makes sense. The ones on the pictures are not exactly like the ones used on our calipers but you get the idea. The seals on the right are the scraper seals, with a square section. [/QUOTE]
I just found this thread looking for PN's for rebuild kits for my 89 S4 calipers. My pucks are the early ones. Just reading the above post I'd offer an edit as the larger seals on the left of the pic are indeed the dust/scraper seals and not the "main seals" as noted. The square cut O-rings are the main seals. Having just removed the pucks from 4 calipers it's clear that the main seals are the ones furthest inboard on the caliper body and held in place by the outward pressure of the puck and inward pressure of the caliper body. If brake system pressure were to meet the outer seals, one pedal pulse would dislodge them instantly I'd think..
The main seals are like the ones on the left on that photo. The inner lip fits into the outer groove on the piston and the outer lip houses a steel ring that holds it in place on the caliper bore top, if that makes sense. The ones on the pictures are not exactly like the ones used on our calipers but you get the idea. The seals on the right are the scraper seals, with a square section. [/QUOTE]
I just found this thread looking for PN's for rebuild kits for my 89 S4 calipers. My pucks are the early ones. Just reading the above post I'd offer an edit as the larger seals on the left of the pic are indeed the dust/scraper seals and not the "main seals" as noted. The square cut O-rings are the main seals. Having just removed the pucks from 4 calipers it's clear that the main seals are the ones furthest inboard on the caliper body and held in place by the outward pressure of the puck and inward pressure of the caliper body. If brake system pressure were to meet the outer seals, one pedal pulse would dislodge them instantly I'd think..
#24
Instructor
The main seals are like the ones on the left on that photo. The inner lip fits into the outer groove on the piston and the outer lip houses a steel ring that holds it in place on the caliper bore top, if that makes sense. The ones on the pictures are not exactly like the ones used on our calipers but you get the idea. The seals on the right are the scraper seals, with a square section.
If I read the tech bulletin correctly, looks like when they updated the outer seal type, they also upped one of the piston sizes from 42 to 44mm. Certainly both changes were made and I think they were simultaneous.
I would suggest UKKid35's photo is of an early caliper with the scraper type dust seal. Nothing missing at all.
#25
Drifting
The engine number ends 606, so it is indeed an early S4, and I believe the front caliper are original (unlike the rears which I have already replaced)
The thing that confuses me is the machining of the circular grove, which doesn't seem to have any function
PS hope to see you at a 928 event one day such as the ones organised by 928.org.uk
#26
Instructor
Thanks
The engine number ends 606, so it is indeed an early S4, and I believe the front caliper are original (unlike the rears which I have already replaced)
The thing that confuses me is the machining of the circular grove, which doesn't seem to have any function
PS hope to see you at a 928 event one day such as the ones organised by 928.org.uk
The engine number ends 606, so it is indeed an early S4, and I believe the front caliper are original (unlike the rears which I have already replaced)
The thing that confuses me is the machining of the circular grove, which doesn't seem to have any function
PS hope to see you at a 928 event one day such as the ones organised by 928.org.uk
By circular groove you mean the cross section of the dust/scraper ring being U shaped? Probably to create the springiness to provide the thrust onto the piston surfaces and keep them clean.
I think I've seen you on 928.org.uk? Yes, once we're able to safely mingle, I will enjoy meeting other 928 owners.