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Brake caliper bores - how do they look?

Hi, I have started on a rebuild of my front calipers for new seals and wipers and got the pistons removed on the first caliper. Looking at the bores it looks like there is some corrosion where the wipers go and maybe some on the bottom of the bores. Should i be conserned about this...? Is this some thing i shoul dsend away to get refurbhised and re-anodized?




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John

1979 930 - mahle 3.4 (7.5:1),Turbokraft longneck IC, Leask WUR w/rpm solenoid,sc cams, rarlyl8 headers, tial wg, 1 bar boost, GT35R
Old 03-01-2018, 11:06 AM
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Get some dental pics and brake cleaner and have at it. You need to remove the metal rings from the old seals.

Lips go towards the rotor when installing the new ones.
Old 03-01-2018, 11:25 AM
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do not scratch the bores and be very carful with the pistons. there is like a ceramic coating on them. just wipe them down.

you WILL need grease on the pistons to get them back in.
after they are in, put a 2x4 in there where the rotor goes then put some air to the caliper, you all 4 pistons popping out at the same time. I did hi and low air pressure.
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Old 03-02-2018, 03:25 AM
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Thanks for the replies,

I'll clean up the rest of my calipers this weekend, and do a update when its all clean.

I soda blasted the calipers on the outside with the pistons in place, will it be ok to sodablast the around the bores or is this a bad idea?

On the pistons from the picture there are small nics as you can see, but they look not to be on the side of the pistons. They were there when i got them out so PO must have had them out at sime time in the past.
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1979 930 - mahle 3.4 (7.5:1),Turbokraft longneck IC, Leask WUR w/rpm solenoid,sc cams, rarlyl8 headers, tial wg, 1 bar boost, GT35R
Old 03-02-2018, 04:43 AM
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I saw the nics.
pistons look to have some stuff on the sides.
if the pistons clean up fine I would not be too concerned about the bores.
the piston seal to the rubber seal is important.

I don't know about soda blasting as in I don't know what it would do.
I don't think it would harm anything,
you saw what it did to the rest of the caliper, you might have to be the judge
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86 930 42kmiles [__] RUNNING:[__] NOT RUNNING: ____77 911S widebody: SOLD
88 BMW 325is 200K+ SOLD
05 BMW 330CI 130K:: [__] RUNNING: [__] NOT RUNNING:
08 VOLVO V70 190K:: [__] RUNNING: [__] NOT RUNNING:
90 B2200[__] RUNNING:[] NOT RUNNING:__2000 MER E320 WAGON [] WRECKED:[]RUNNING:
Old 03-02-2018, 05:25 AM
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Thanks,

Soda blasting cleaned the calipers nice without hurting the anodizing, the sides of the pistons is just gunk, so i think they will clean up nice except for the nics on the bottom.
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1979 930 - mahle 3.4 (7.5:1),Turbokraft longneck IC, Leask WUR w/rpm solenoid,sc cams, rarlyl8 headers, tial wg, 1 bar boost, GT35R
Old 03-02-2018, 05:36 AM
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I'd use a light touch and a scotchbrite pad on the bores before I'd blast them. You just want to knock off any debris or corrosion. The goal is to have the pistons able to move without getting hung up on anything in the cylinder.
Old 03-02-2018, 06:19 AM
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i would not use anything like sandpaper which is what a scotchbrite pad is.
I just don't think it is necessary and could remove any protective coatings.
you remove a protective coating then you could get corrosion and pitting down the road.
just my opinion.
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86 930 42kmiles [__] RUNNING:[__] NOT RUNNING: ____77 911S widebody: SOLD
88 BMW 325is 200K+ SOLD
05 BMW 330CI 130K:: [__] RUNNING: [__] NOT RUNNING:
08 VOLVO V70 190K:: [__] RUNNING: [__] NOT RUNNING:
90 B2200[__] RUNNING:[] NOT RUNNING:__2000 MER E320 WAGON [] WRECKED:[]RUNNING:
Old 03-02-2018, 07:07 AM
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I have to confess, I've never opened up a turbo caliper--I had assumed there were no coatings, so my apologies. I was just going on my experience with other calipers (and most of those were on older BMWs).
Old 03-02-2018, 08:07 AM
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that's ok.
it may not hurt it no need to risk it.
I think I used a tooth brush but then mine where in good shape.
really just wanted to clean the groove the inside seal came out of, which was the only one I replaced
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86 930 42kmiles [__] RUNNING:[__] NOT RUNNING: ____77 911S widebody: SOLD
88 BMW 325is 200K+ SOLD
05 BMW 330CI 130K:: [__] RUNNING: [__] NOT RUNNING:
08 VOLVO V70 190K:: [__] RUNNING: [__] NOT RUNNING:
90 B2200[__] RUNNING:[] NOT RUNNING:__2000 MER E320 WAGON [] WRECKED:[]RUNNING:
Old 03-02-2018, 10:40 AM
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If you were running non-silicon brake fluid, remember that it is water soluble, so you can simply use hot soapy water to clean them up. Just remember to dry them out with compressed air.

Mark
Old 03-02-2018, 04:43 PM
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Howdy,
Once all of the seals are removed soda blasting should be OK for the bores. If anything the soda blast may reveal some pitting or other flaws.
Remember, the surfaces that need to be golden are the primary seal GROOVE and the associated piston surface.
Gary
Old 03-02-2018, 07:31 PM
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I am just starting on my '78 930 calipers F & R.

ordered a rebuild kit thinking I would just replace everything. $700 for the seal and scraper rings from Porsche WHOA. this is a full tub up restore so planning to be sure everything is like new when done. building my dream car.

I picked them up for my SC/930 conversion project.

after looking at them closely, they look to be in great shape.

so I pop the pistons out of one and all is good. the seals and scraper rings seem to be in great shape, pistons flawless, bores good.

found a very small amount of corrosion in the seal slot that I easily removed with a small pick. seal looked perfect.

after cleaning, lubing, and reinserting the pistons, they push in easily with finger pressure and pop out with very little air pressure. vendor agreed to take the rebuild kit back. I had no idea the kit for 930 would be so expensive. I got the kit for the calipers on my 951 track car, don't recall the price but sure it was modest compared to these.

good luck.
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Old 03-03-2018, 05:53 AM
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Again thanks for all the replies, have now removed all seals and scrapers and cleaned as best i could, stil some small places i can scrape off some corrosion. Primarely under the upper lipp that keeps the seal in place.

Here are some pictures of the worst bores. Are these ok or should i send them of to a place like PMB performance for restauration?



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1979 930 - mahle 3.4 (7.5:1),Turbokraft longneck IC, Leask WUR w/rpm solenoid,sc cams, rarlyl8 headers, tial wg, 1 bar boost, GT35R
Old 03-04-2018, 10:13 AM
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Looks like you still have some cleaning to do, the groves the square seals go in. That's where you need the dental pics, they have curves for getting in those hard to get to places.
Old 03-04-2018, 01:50 PM
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Yes still scraping, the dental tool i got doesn't get the inside corners to good so will try to buy an other one today.

As for the pitting and places the anodizing is gone. Will this cause me problems down the road?
also since I'm scraping of corrosion in the grove the piston seal is in, when i replace the seal will it seal?

Just trying to avoid spending $150 for each caliper in seals and scrapers to find out it's leaking or discovering 2-3 years down the line that corrosion is making problems for me.
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1979 930 - mahle 3.4 (7.5:1),Turbokraft longneck IC, Leask WUR w/rpm solenoid,sc cams, rarlyl8 headers, tial wg, 1 bar boost, GT35R
Old 03-04-2018, 11:16 PM
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The groove is the major area of importance, that is where the fluid seal goes. The scraper is a dust boot, the lips on it face the rotor when installed and just keep out dirt. They have nothing to do with retaining fluid.
Old 03-05-2018, 12:16 AM
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i did not replace the scraper rings, the outer ones, when I did mine, too much $$
could not justify spending that much for a rubber seal
mine where ok
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86 930 42kmiles [__] RUNNING:[__] NOT RUNNING: ____77 911S widebody: SOLD
88 BMW 325is 200K+ SOLD
05 BMW 330CI 130K:: [__] RUNNING: [__] NOT RUNNING:
08 VOLVO V70 190K:: [__] RUNNING: [__] NOT RUNNING:
90 B2200[__] RUNNING:[] NOT RUNNING:__2000 MER E320 WAGON [] WRECKED:[]RUNNING:
Old 03-05-2018, 03:03 AM
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Some of my scraper rings where pretty bad\torn so no choice on replacing them.

I see URO makes a caliper seal kit with the seals and scrapers for $32 each caliper any one have experience with the quality of these? sure beats $150 for the porsche ones.

PO930FBCKIT and PO930RBCKIT
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1979 930 - mahle 3.4 (7.5:1),Turbokraft longneck IC, Leask WUR w/rpm solenoid,sc cams, rarlyl8 headers, tial wg, 1 bar boost, GT35R
Old 03-05-2018, 04:31 AM
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I found PORSCHE seals pretty cheap, don't remember where.
as long as they are genuine Porsche.
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86 930 42kmiles [__] RUNNING:[__] NOT RUNNING: ____77 911S widebody: SOLD
88 BMW 325is 200K+ SOLD
05 BMW 330CI 130K:: [__] RUNNING: [__] NOT RUNNING:
08 VOLVO V70 190K:: [__] RUNNING: [__] NOT RUNNING:
90 B2200[__] RUNNING:[] NOT RUNNING:__2000 MER E320 WAGON [] WRECKED:[]RUNNING:
Old 03-05-2018, 05:04 AM
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