Multiplex

Hey Guys,

I've started on a rebuild of my 4pots calipers. I still need to order some of the rebuild parts since I first wanted to take the calipers appart to see if they are usable.

Anyways, today I got the driver side one appart so I desided to post some pics and get your oppinion on it. Its the first rebuild i am doing so

I'll be taking loads of pictures and if the feedback here is good, I'll be doing a full writeup page on my website!

Calipers itself look good. Inside is rust free, only the part above the sealing ring is dirty and a little rusted, nothing sanding it a bit wont fix. I'd assume anything outward from the seal rings don't matter to much....


I'm not entirely sure about the pistons though. One came out easilly, the other 3 I had to use some accesive force. They look good enough except for the middle one. Inside and top are pretty rusted but they seem clean and smooth enough where it matters. Not sure though, some good info on judging this would be greatly appreciated!


One last shot, just to show you what a wire brush can do


I'll be painting the calipers red after cleaning them, I'll be sure to show you guys when that is done

Matlock

When I did mine I consulted the FSM and it says NOT to take them apart/seperate. Don't know.

Multiplex

Owh yeah, I noticed that two now..

No idea why that is. Maybe they are hard to align or something? I wouldn't have been able to get the pistons out without taking them appart so we'll see how this ends up.

Anyone have any idea about this?

*edit* I must say I found the FSM pretty useless on this subject anyways.

pip

But if hes rebuilding them they have to come apart.

Wankel7

^^^^^^No they don't. I had no problem doing mine together.

Actually, the FSM is of great help. It says do not seperate the halfs.

I just had to use a combo of adj. wrenchs and wood blocks to get all the pistons out.

I sure hope you get those things back together and working.

When you say you had to use, "Excessive force", to get the pistons out what are talking about? Did you pry them out or something? You are supposed to use compressed air to pop the pistons out. Just wondering.

James

Multiplex

James, I tried compressed air, it got one piston out, the other 3 stayed in. I'll try that again withe the other caliper that is still in one piece.

I used a combination of heating the calipers and using a wrench to pull them out. That worked eventually. It did damage the top of one of the pistons (the one that was most stuck) but I am unsure if this really matters, its the part that sticks out and presses against the brake pads and those are rusted anyways so a couple of scratches there shouldn't make much difference. Still if I can I may replace the pistons.

The calipers themselves still look very good indeed. Mind you, I did not have any leaking problems, I desided to rebuild because even brake force on the brake paddle didn't lodge a couple of the pistons.

If anyone has any usefull info about WHY you shouldn't take the two halves appart, please let me know. Friends of mine who've rebuild calipers for other cars do this regularly. The calipers of my Delorean where totally taken appart aswell as they had to be widened to accept vented disks and they have given me 0 problems.

89GTUs Lady

The reason you are NOT supposed to seperate the calipers is because you can NOT get the o-rings that go between the halves. The part number does not exist. Good luck trying to find them.

Matlock

Like the PS pump there is a sealing washer (aluminum, not sure what the calipers use) that does not exsist. Once pulled apart it genrally leaks, I found this out. I would suspect the chances of a leak are multiplied in this situation as well. 1000psi is a lot of pressure to hold.

Multiplex

Ah yeah, they where rubber washers in my calipers. I still have them and they look ok enough, and else I'll have to get something that matches. We'll see what happens.....

den

When you tried using compressed air to get the pistons out what pressure did you get up to ? When i rebuilt mine it took over 150 psi to pop 3 of the pistons out, the last one wouldn't budge. It was rusted as bad as the ones in your pic, while still under pressure i gently tapped it all around the groove unitill it poopped out aswell. I would make absolutley sure the two halfs dont leak when you get them back togeather, your really not meant to seperate them.

Multiplex

den, no idea, something like 7 or 8 bar I think (sorry dont know psi scale). I'm gonne try and do the other caliper the official way. No turning back on the caliper I got taken appart now huh

Matlock

Yeah all you can do is try and hopefully it won't leak for you. Don't take my critiscm as an insult, just pointing it out to you.

Multiplex

Matlock, ah its worth the experiment

Real question will be how good the washers still are and if I can tighten it enough to keep it from leaking. I am hopefull since they are rubber or something like that, which seals a whole lot better then a solid aluminium ring. And if they do leak, well then I guess I'll just have to get another set of calipers from the junkyard

den

I would try to find some kind of replacement washer to increase the chances of getting good seal. Even if it comes to it a second hand set isn't going cost you that much.

Wankel7

When I did my calipers I did this.

First I was using about 35 psi to get them out. When I put the pressure on one piston popped out. So then I just barely slide the first popped piston in just enough to seal. I then put a piece of wood against the piston I just slid back in. So, now I have two pistons blocked. I apply airpressure again. Pop, one of the two free ones goes.

I just did stuff like this until I got them all out. I even used a large adjustable wrench to pin a freshly popped piston in place so I could get the other one out. It took me two hours for two calipers. However, they were not in bad shape.

I would say that if you simply can not get the piston out it is time time to put it back together and get a rebuild from Advance Auto or Auto Zone.

And for rebuild kits, www.mazdaformance.com is your cheapest bet. Unless, you are with mazdacomp then that is the cheapest

James

Multiplex

James,

I'm at the wrong side of the ocean for that sorta thing I'll put the caliper back together and see if it will work. If it does, great thing, if it didn't it still served its purpose by teaching me how to rebuild a caliper (and what not to do). Better waiste some time on a caliper I would be replacing anyways, then screw up a perfectly good caliper

The passenger side caliper I am going to try and do with airpressure purely. I got as far as one piston out and one half out basically doing what you described. Maybe I just need to learn some patience and alot of WD40

Wankel7

DOH, I just noticed you are a pond away

Good luck with man. I hope you get it worked out!

When you slide a freshly popped piston in you just want to slide it in enough to seal (not much) and you can still get it out with your fingers....or some airpressure. And of course you can take off those piston boots while you are doing this.

James

Multiplex

Wankel7,

I took the piston boots off already, best way to get loads of WD40 on the spot

Turbonut

iTrader: (1)

Just a FYI-Spraying WD40 onto the piston after removing the dust seal will only "hit" the outer part of the piston. The piston becomes stuck in the bore because of contamination on the other side of the piston seal, which the WD 40 will not contact. A lot of air pressure and wood blocks. It's usually the lower pistons that become stuck because of condensation settling in the bottom of the caliper.

Multiplex

Turbonut, so far the pistons I have removed got stuck by junk and rust above the seal, not below it. Actually everything looks surpisingly well below the seals so maybe my compressor just doesn't have enough pressure

But you are right, WD40 in this case is no mirracle cure, but it does help somewhat.

bingoboy

if you do a full writeup, please don't include pulling the 2 halves of the calipers apart. the last thing we need are people doing this who cannot get them put back together correctly following these instructions and then hurting themselves.

Multiplex

bingoboy will definately do so and include a big warning in it

thats the whole point of this thread, getting info on what I do right and what I do wrong. If I mess up these calipers I wont loose a minute of sleep over it, I'll just get another set, I might do that anyhow to get some spare pistons to replace the ones that are bad. If someone else messes up their calipers and put them on their car, I will loose sleep over that!

Btw, that reminds me, is there any difference between driver side and passenger side calipers or are they interchangable. Only thing I can think off is that the brake line is fastened at a different place.

bingoboy

also if you score the sides of the pistons (the part that needs to be sliding, the top lip doesn't actually recess into the caliper) while getting them out, you don't want to use them again.

Multiplex

Bingo boy, I got one whose edge is damaged that way, one more reason to get an additional caliper to replace the one I have in case it does leak and get some spare pistons. The piston I scratched might have to go anyways cause its the most rusted.,

The other 3 are good, only one has some rust I am slightly worried about. Again, a good reason to get a spare caliper.

Multiplex

Okay guys, nice news. I gave my other caliper another try. After removing the dust covers yesterday and soaking them in WD40 I had alot more luck. One piston was already out, the second now came aswell. Upping the pressure to the fullest my trusty cheap hobby compressor could do, and trying to somehow stop air from escaping around the nossle using some cloth (anyone got a good suggestion for this) I got the last two pistons to move but not come out far enough.

The rest I did just by grabbing them with some tool (no idea what it is called in english) and pulling them out (only on the outer rim, never the piston body). That still took some work but I managed.

Inspecting the caliper I found the same thing as with the first one. The bores look good, only the part on the 'outside' is dirty.

The pistons look pretty okay, some rust on 2 of them, one I have doubts about.

My camera was drained so I am charging it now, when its charged I'll recreate some action shots and get some detailed shots of the calipers and pistons. I'll also start working on the writeup.