1988 Rear Brake Caliper Internal Piston Seal Found (works for Pre-88 too) (Page 1/3)
Silicoan86 APR 15, 06:17 PM
Centric Seal Kit part number 14362008

CAUTION: It is very important that you take extreme care and thoroughly inspect and clean ALL of the internal parts when taking on this project. Pay special attention to the thrust washers for any cracking or debris and to the piston bore for any pitting or debris. Any damaged or defective parts should be replaced and should NOT be used.

I was recently attempting to rebuild the rear calipers for my '88 coupe and discovered that some fluid had leaked past the internal piston seal. I disassembled the pistons and found that both the internal piston and the inside bore of the outer piston were in good shape with no pitting, but the seal itself felt soft.



For many years this seal has been deemed unobtainable, and as such, the pistons have also been deemed as non-rebuildable. I spent some time browsing various sites hoping to find a kit that contained the seal, possibly from another GM car. I read about how the Pontiac 6000 shares some caliper parts with the ’88 Fiero so I focused my search there. I found this kit made by Centric on RockAuto listed for a Pontiac 6000 that showed the seal in multiple pictures. I searched Google for that part number and also found the kit available on Amazon, with a different picture that also showed that particular seal in the kit. Turns out the kit cross references to the pre-’88 Fiero as well as 1982-1988 F-bodies. I ordered 4 of them immediately. Note: only 2 kits are necessary (1 for each rear caliper).





A few days later the kits showed up and it was confirmed, not only was the seal included in the kit, but it was also the correct seal for use on the ’88 Fiero. It was noticeably firmer than the old seal that had softened over time, and fit beautifully around the internal piston and sealed very nicely inside the outer piston. I reassembled both pistons and calipers using the new internal seal from the Centric kit, and used the rest of the seals from a 1988 specific seal kit. As it turns out, the internal piston parts are the same between all Fieros, but the O.D. of the main piston is slightly larger on the ’88.



I’ve reinstalled everything back into the car and plan to bleed the brakes tonight and verify that nothing leaks, but based on how well it appeared to seal when I had the caliper on the bench, I’m pretty confident that my leak will be solved.

[This message has been edited by Silicoan86 (edited 04-17-2016).]

Silicoan86 APR 15, 06:18 PM
Some step by step pictures of the piston rebuild process:

New seal installed on the internal piston



Piston in a piston





Spring Installed



First washer



Bearing washer



Last washer



Retainer/Cover



Be sure that the washers are all aligned before pressing the retainer/cover into place or you will increase your risk of damaging them



Press slowly and carefully, stopping every once in a while to verify that everything is still properly aligned



I left one piston fully assembled for reference while I rebuilt the other one. I was unable to find a dimension as to how far I should press the retainer/cover back on, so I pressed it back on enough to match the one that I hadn’t taken apart yet. This was that dimension.







Back on the car


seajai APR 15, 06:28 PM
Just ordered the kits from Rockauto today to rebuild all 4 calipers on the wife's car. How did you take the pistons apart to begin with? Any pics of the disassembly process?
Silicoan86 APR 15, 06:30 PM

quote
Originally posted by seajai:

Just ordered the kits from Rockauto today to rebuild all 4 calipers on the wife's car. How did you take the pistons apart to begin with? Any pics of the disassembly process?



I used the flat end of a 3/16" drill bit inserted through the hole in the face of the piston and pressed everything out on a bench vise with the help of a large socket on the other side. Be VERY careful while pressing this out as I've heard of others cracking the washers inside during this process. The risk will be magnified if everything does not remain properly aligned during the entire pressing process.





[This message has been edited by Silicoan86 (edited 04-15-2016).]

FTF Engineering APR 15, 08:43 PM
Cool. Glad that did work out like we were discussing in that other thread.

So those things you're calling flat washers are hardened steel thrust washers for the bearing and they are the ones that I've seen crack upon disassembly. Hopefully doesn't happen often, but remember to inspect very carefully.

Here's the thread that started this. There's some other detail in there that might be helpful:
http://www.fiero.nl/forum/Forum1/HTML/096596.html

on edit - fixed link

[This message has been edited by FTF Engineering (edited 04-16-2016).]

theogre APR 16, 03:29 AM

quote
Originally posted by FTF Engineering:
Cool. Glad that did work out like we were discussing in that other thread.

So those things you're calling flat washers are hardened steel thrust washers for the bearing and they are the ones that I've seen crack upon disassembly. Hopefully doesn't happen often, but remember to inspect very carefully.

Here's the thread that started this. There's some other detail in there that might be helpful:
http://www.fiero.nl/forum/Forum1/HTML/096596.html

Nice article but many will see this as safe easy and quick...

Read that thread because covers some issues/problems. (Edit link... suppose to be 096596.html )
May look easy to do but can bite hard down the road. If or When you have problems, you could be in big trouble.
Same problems w/ many rebuilt calipers at stores and online than have rebuilt pistons. Many pistons have been rebuilt before that could weaken the back cover.

Note that Three 84-87 pistons:
Older w/o 4 notches to accept stamped pad clip
Newer w/ above.
Recall pistons

Older Seem to have same thrust bearing shown. (I'm not tearing one apart.)
Newer have same bearing shown.
Recall piston have no hole in the front of outer piston, black oxide finish and better thrust bearing. (Weak bearings is part of recall problem.)

------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)


The Ogre's Fiero Cave

[This message has been edited by theogre (edited 04-16-2016).]

hobbywrench APR 16, 11:22 AM
silicoan, Great pics and article. Thanks for the effort!!!
Silicoan86 APR 17, 03:29 AM
Great points brought up by the ogre and FTF. Although the process isn't much more difficult than rebuilding the calipers, it is critical that extra care is taken to fully inspect and clean all of the parts. I added a note about that to the original post.

I got the car back together tonight and back on the road. I also rebuilt the front calipers, replaced the rotors, pads, and hoses all around, and installed new parking brake cables. The brakes feel fantastic now and it's nice to finally have a functional parking brake!
Silicoan86 APR 27, 12:39 PM
Almost two weeks later... the calipers are leak free and the brakes feel awesome.
seajai APR 27, 02:42 PM
Just did mine. Glad I did, the inner pistons were all full of rusty sludge.