So I'm rebuilding some rear calipers and I have some questions... I'm also posting some pictures so those that want to do this will have some idea of what they're getting into. I bought a set of 88 rear caliper rebuild kits from The Fiero Store and a set of used calipers. Rather than just clean them up, I feel more confident rebuilding them first.
Here are the calipers...
Pins have to be pressed out through the front..
Here I have removed the front seal, the brake line, ebrake lever, and also checked to be sure that the bleeder screw will come out...
When you pull the body of the caliper apart and press out the piston, this is what you will have in front of you
This is the caliper spread out along with the Fiero Store rebuild parts laid out below
Now, for my question. Is there a way to check the piston to be sure its good? Is there anything I need to check concerning the piston? Replacing the seals and washers is the easy part, so is the cleaning. I'm just unsure if its this straight forward or if I need to inspect the piston.
Look for any major pitting on the piston. Run your fingers around it and feel for any gouges and such. If it feels good, clean it up and reassemble. The second to last picture looks okay, but looking at it here is different from feeling it in person. The head of it looks a tad bit beat up, but as long as the body itself is still smooth, it should be okay.
[This message has been edited by Fiero84Freak (edited 06-08-2009).]
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02:54 PM
FTF Engineering Member
Posts: 710 From: Near Philadelphia PA Registered: Sep 2001
Originally posted by Jncomutt: Is there a way to check the piston to be sure its good? Is there anything I need to check concerning the piston? Replacing the seals and washers is the easy part, so is the cleaning. I'm just unsure if its this straight forward or if I need to inspect the piston.
Pull out the old "two way check valve" in the middle of the piston face (the little yellow plug in your pic) and see if there is any brake fluid behind it.
If there is any fluid behind that yellow plug, then the pistons need to be replaced. Pull the "valve" and set them face down on some paper and let them sit like that for a few minutes.
Thanks for the tip, that's the kind of suggestion I was looking for. Its probably going to be raining all day tomorrow but next chance I get I'll do that to each one.
Can I pull the "valve" and let them sit while they're still assembled? I have a few calipers I can test this way if thats the case. Would save the time of disassembly.
------------------ 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)
Pull out the old "two way check valve" in the middle of the piston face (the little yellow plug in your pic) and see if there is any brake fluid behind it.
If there is any fluid behind that yellow plug, then the pistons need to be replaced. Pull the "valve" and set them face down on some paper and let them sit like that for a few minutes.
I bet they're shot...
Im asking because I don't know, but isn't what you said in you post one of the reasons for rebuilding the caliper in the first place. In other words, when brake fluid leeks out of the yellow valve, its time for a rebuild? I have a 88 rear passenger caliper that had brake fluid leeking out of the center after I "screwed" it in for a pad change. I noticed fluid leeking after i had pushed it back, so I figured I needed a rebuild and just replaced that caliper with another one. I was always just going to rebuild it, but your post leads me to believe that its shot. So again, what is the reason for a rebuild if your caliper is NOT leeking from that spot.
Rob
------------------ 88 TTop coupe (96 3.4DOHC/5 speed) 03 Vibe GT. 6spd (stock) 05 GTO, LS2, 6spd (not stock) 84 SE "Vert" (oh boy, what did I do now)
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09:25 PM
FTF Engineering Member
Posts: 710 From: Near Philadelphia PA Registered: Sep 2001
Those rear pistons have to be the stupidest, most irresponsible piece of design crap I think I've ever seen on a car. I have no idea what they were thinking.
When GM goes out of business, maybe you can send them that piston back with a note telling them it's designs like that which helped cause them to be in the position they're in right now...
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09:37 PM
FTF Engineering Member
Posts: 710 From: Near Philadelphia PA Registered: Sep 2001
Im asking because I don't know, but isn't what you said in you post one of the reasons for rebuilding the caliper in the first place. In other words, when brake fluid leeks out of the yellow valve, its time for a rebuild? I have a 88 rear passenger caliper that had brake fluid leeking out of the center after I "screwed" it in for a pad change. I noticed fluid leeking after i had pushed it back, so I figured I needed a rebuild and just replaced that caliper with another one. I was always just going to rebuild it, but your post leads me to believe that its shot. So again, what is the reason for a rebuild if your caliper is NOT leeking from that spot.
Rob,
If you've got fluid coming out of that hole in the center of the piston, the problem is actually deeper than that little yellow plug. The little yellow plug is actually a two way air filter valve to allow air into and out of the cavity behind it. That cavity BEHIND that vent (plug) is supposed to have nothing but AIR in it, and if there's brake fluid in that cavity behind the plug, it means that the piston is leaking INTERNALLY.
The plug itself isn't really the problem, it just hides the problem for a while until it gets so bad that it starts leaking out of the center.
The only reason to rebuild a rear caliper (of any year) is if you are leaking fluid from the large ring seal that goes around the outside diameter of the piston or if you're leaking fluid out the parking brake actuator hole. Those are the only things that the rebuild kits will address. No rebuild kits will do a darn thing about the pistons that are leaking internally.
Don't know. Design same but may not fit for other reason.
------------------ 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)
If you've got fluid coming out of that hole in the center of the piston, the problem is actually deeper than that little yellow plug. The little yellow plug is actually a two way air filter valve to allow air into and out of the cavity behind it. That cavity BEHIND that vent (plug) is supposed to have nothing but AIR in it, and if there's brake fluid in that cavity behind the plug, it means that the piston is leaking INTERNALLY.
The plug itself isn't really the problem, it just hides the problem for a while until it gets so bad that it starts leaking out of the center.
The only reason to rebuild a rear caliper (of any year) is if you are leaking fluid from the large ring seal that goes around the outside diameter of the piston or if you're leaking fluid out the parking brake actuator hole. Those are the only things that the rebuild kits will address. No rebuild kits will do a darn thing about the pistons that are leaking internally.
Does that make sense?
FTF E
Got it. Thanks I guess I will be looking for a new piston.
Thanks
Rob
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04:50 PM
FTF Engineering Member
Posts: 710 From: Near Philadelphia PA Registered: Sep 2001
Got it. Thanks I guess I will be looking for a new piston.
Yeah, sorry to be the bearer of bad news, but wait... it gets worse.
I'd bet real money that you won't find just the piston. At least not as cheaply as you can find entire rebuilt calipers (which are supposed to have a repaired or replaced piston installed by the rebuild shop).
If you're leaking out the hole in the center of the piston face, I would recommend that you just go get yourself a set of rebuilt calipers and use yours as the core All for one stupid fifty cent seal that GM decided you aren't supposed to mess with.
Can I pull the "valve" and let them sit while they're still assembled? I have a few calipers I can test this way if thats the case. Would save the time of disassembly.
Sorry... I missed that question earlier.
Absolutely. You can check for fluid behind that plug with the caliper fully assembled. Just pop out the plug in the center and set them in an orientation such that the hole is down and let gravity do it's work. Maybe stuff a couple of wadded up paper towels in there to take up the space and you're good.
Or bad...
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10:12 PM
FTF Engineering Member
Posts: 710 From: Near Philadelphia PA Registered: Sep 2001
Wow that sucks... Stupid things. I don't know how much I trust a set of autozone calipers either...
Yes, it does suck. And the worst suck is that there's really even no reason for it!! There are other car manufacturers who have figured out a parking brake on disk brakes without having this problem. Lots of them. GM just missed the mark with this one.
I hear you about the rebuilds... I've heard lots of horror stories about people getting crappy rebuilds and it seems like luck of the draw. You may get one that was done by someone who had skills, or you may get one that was done by someone that was brain dead and had no clue what they were doing.
I cannot condone this behavior, but what I did....
I took my old pistons apart. Yes, you aren't supposed to, but I did anyway. I took them apart, cleaned out all the goo, and put them back together with the same original fifty cent seal inside. Of course, it will occur again, but I decided that taking them apart and cleaning out all the goo every few years was a better alternative than sending my original calipers as cores.
You know... My original ones that weren't all rusted or mangled up by the brain dead idiot at the rebuild shop.
As it turned out, I only had to do it once in almost 20 years of Fiero ownership. I lubed the internal seal a little before I reassembled the piston and I suspect that GM never did that in the first place. That omission may have helped lead to the failure.
Of course, due to the liability and safety issues that are inherent in any brake work, I cannot condone this behavior or recommend that anyone else do the same, but that's what I did....
Here's a good cross section diagram of the rear pistons.
The seal labeled "Piston seal" is the one that DOES come in a rebuild kit, but the internal seal that makes it leak out the center hole is the unlabeled black band wrapped around the blue part. That one does NOT come in a rebuild kit.
Jncomutt, Sent you another PM.
FTF E
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09:38 AM
Daredevil05 Member
Posts: 2345 From: South Jersey 08077 Registered: Oct 2006
Originally posted by FTF Engineering: ....but the internal seal that makes it leak out the center hole is the unlabeled black band wrapped around the blue part. That one does NOT come in a rebuild kit.
If I recall, one of our members spent a considerable amount of time looking for a replacement, from a large variety of sources, for that one and came up empty.
They were probably thinking, "What kind of screwball design can we come up with that won't infringe on somebody else's patent, that we will then have to license from them?" A lot of this goes on in the automobile industry.
Originally posted by carbon: www.caplipersonline.com NOS front 88 calipers and rebuilt rear 88 calipers... this is where I got mine when I did my brakes 5 years ago... worked great.
Yeap. It said "1 remaining" for each. As soon as I went through the check out (rock auto), the part number wouldn't come up on their website when I searched it anymore. Even if you search through google and click on the link, it will bring you to a "part not found" page.
[This message has been edited by Jncomutt (edited 06-19-2009).]
I just wanted to be sure that the plastic washer goes against the caliper body and the rubber seal goes over it. This is how they were when I removed them, but I don't know if they were tampered with by the previous owner.
I'm thinking the parts are in order as I laid them out above but I wanted to be sure.
