brakes Broken Brake Caliper Piston

['76mintgrün'02]

Thanks Charlie!

That is a good tip. 

I have also heard of people putting bearings in the freezer to shrink them prior to install.

I like the fixes where you walk away and come back later.

 

Another way to use cold to break things free is to turn a can of compressed air upside down (like the stuff sold for blowing out computers) and point the little straw at the offending fastener.  It will turn frOsty cold instantly.

 

(I have seen videos of people removing dents from body panels using the can-of-air, followed by a hair dryer.

I have not tried it though)

 

I was worried about the difficulty of getting the grease out of the caliper, but the bulk of it, which was in the cylinders, just fell out; due to the residual brake fluid.  Like little grease 'castings'.  I then blew from all directions with compressed air @ 150 psi.  

 

Paul's comment about the dangers of Brake Kleen type products confirms my concerns.  I have not shot that through the caliper, although I did use it to clean the outsides.  

 

I am wondering how concerned I should be about traces of grease in the caliper.  I am considering warming the caliper in the oven and then blowing it out again.  Possibly rigging a way to force brake fluid through while it is warm as well.  I have time to get it clean while I am waiting for pistons to arrive.

 

tzei did mention using a master cylinder to force the stuck one out.  He uses a spare pedal box, which I do not have.  The grease was a very gentle slow way to extract it.  I just hope the residue will all come out and not be a problem in the future.

[Simeon]

 

tThose are not torx bolts- they are 'spline drive'- if you look very carefully, you can see the difference.  I have no idea where to get those drivers...  you could, of course, make one relatively easy in a very accurate mill with an indexing head...

 

And I'm surprised no- one's posted this- you can pretty easily rig a brake master and make up a lever assembly to use brake fluid pressure to pop the pistons out.  But that's super- dangerous, since spraying brake fluid's right

up there with diesel injection pump pressures...

 

t

They are called 'Ribes' apparently. I had never heard of them before. A good thread:

http://www.bmw2002faq.com/topic/165539-reviving-the-tii-after-five-years-hibernation/page-2

['76mintgrün'02]

That was a GREAT thread.  I just reread it and this line caught my attention,

 

I only cracked these calipers because I want to treat the rust in the cylinder above the seal.

 

 

I am pleased with how the tool I made removes this rust, without having to split the calipers.  It seems like a simple solution to a common problem.  

 

If there are more weirdos like me (and JohnH -- no offense) out there that want to revive their calipers, this is the tool for you : )

 

The FedEx man just dropped off my two new pistons, so I can finally get back to the fun.  

[Simeon]

I am thinking about rebuilding the old calipers that have been lurking under my bench for a few years. After a few bad experiences in the past resealing brake hydraulics badly I adopted a policy of only buying new or factory rebuilt brake parts. This is starting to get an unsupportable position, especially with RHD braking components. Even calipers seem fraught with difficulties with new rebuilds with odd castings.

[JohnH]

The calipers I rebuilt in that thread were originally bought in rebuilds and appeared to be made up of non matching halves. I'm not convinced that non factory rebuilds are always up to scratch. I think that the techniques rebuilders use, of wetting pistons and seals with brake fluid, rather than red grease leads to their early demise, especially if they are not used very much.

 

As far as splitting the calipers is concerned, I have no problems with it so long as the square section o-rings are available. There is nothing special about the bolts other than their RIBES RM6 heads. They are standard metric M9 class 8.8 bolts and pinch lock nuts both with a black oxide finish.

 

As far as calipers finish is concerned, the original passivated zinc may look nice, but does it last in day to day use. Maybe in dry desert areas but certainly not here in the UK.

 

Finally, sometimes pistons just wont come out and you do have to use stillsons on them, but I find thats a rarity and LIGHT tapping with a 1/2lb ball and peen hammer using a strikethough screwdriver to angle the taps outwards/upwards and all around the rim, tends to walk the piston out. It may take a few minutes of tapping to do the job however.  

[Simeon]

Haven't heard the term Stillsons in years . Thanks for your great post

[Hans]

Somewhere I read that those bolts were one time use only, for what that's worth. I managed to source some direct from ATE in Germany many years ago. Also be VERY careful when using air pressure to blow out pistons. Crap goes everywhere.

['76mintgrün'02]

Also be VERY careful when using air pressure to blow out pistons. Crap goes everywhere.

 

Agreed, I put mine in a large zip-loc bag for that step.  Having a thin (1/2") piece of wood between the calipers while blowing them out, keeps them from coming all the way out and spraying fluid everywhere.  You then have to wiggle them out the rest of the way. 

Edited July 11, 2015 by '76Mintgrun'02

['76mintgrün'02]

I think that the techniques rebuilders use, of wetting pistons and seals with brake fluid, rather than red grease leads to their early demise, especially if they are not used very much.

 

I bought a little tube of 'caliper grease' at the parts store, but have not been sure about how much and where to use it.  The tube says 'contains petroleum distillates' and I am afraid that might not play well with the rubber seals.  Reading online yields mixed information, from 'only use brake fluid during assembly', to 'slather them up with grease'.  I am the conservative sort and have assembled the first one using brake fluid only.  It would take two minutes to have the pistons back on the bench and be smearing grease in the bores, if I knew that was what I should do.  I can definitely see the rust prevention benefit, I just wonder about the grease mixing with the brake fluid. I suppose the key is in choosing the right grease.  I can see what else NAPA has to offer (one mile from my house).

 

I understand the 'do it right, do it once' mentality and I do want to do it right, but I also know I will be getting back in here before too long to replace pads and rotors.  I have both, but may change my mind on the pad selection.  The reason I am not installing the new parts now is because it stops very well and the back brakes will also be gone through when I swap rear sub-frames with one I am refreshing.  I figure new front and back at the same time makes the most sense, but involves more work 'doing it twice'.

 

I wondered about the originality of the calipers I am working on.  I believe they probably are the ones that came on the car.  Part of the reason is that the pistons are not all the same.  There are a few that were rustier on the end and have some pitting and I am guessing they are originals and the others were replaced over the years... in the original calipers.

 

I put the two that have some pitting on the end in the lathe and skimmed them back to smooth metal, where they will contact the back of the pad.  I took photos, but... Full bucket = problem. 

 

edit: I looked online to try and find the red grease that John used and it is only available in the UK... how weird is that?  I would like to put some under the boots during the next 'service session'.  I will use that stuff I bought from NAPA on the pin ends, but that is about it.

 

http://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=p2047675.m570.l1313.TR0.TRC0.H0.TRS0&_nkw=CASTROL+GIRLING+RED+RUBBER+GREASE+BRAKE+GREASE+&_sacat=0

Edited July 10, 2015 by '76Mintgrun'02

[JohnH]

I use Miller Red Rubber Grease, which I see is available from http://performanceracingoils.com/classic-ancillariesspecialty-oils-c-2_37.html

 

I know that Lubricants and greases are much cheaper in the US, than the rest of the world, so $20 + shipping may seem expensive, but it will last you (and your successors) a lifetime.

 

There is an interesting discussion about RRG in this forum http://www.xs11.com/forum/showthread.php?t=41610

 

http://www.redrubbergrease.com/ shows how to use it, though I'm not sure where this site originates.

 

As far as mixing stuff with brake fluid is concerned, if its not hydroscopic and doesnt attack seals and other components then I dont think it really matters, but I may be wrong! 

Edited July 11, 2015 by JohnH

[Simeon]

It is specifically designed for brake assembly, so I doubt it could have a bad effect on rubbers. If there is a thin coating on the area of bore above the seals and where they do not run in normal use then I struggle to see how it can cause any harm.

['76mintgrün'02]

Thank you again for the added input.  I would have used that red rubber grease, if I'd had it on hand.  

 

All I had was a small tube of Permatex Ultra Disc Brake Caliper Lube.  I smeared a little of that on the inside of the pistons and put a little on the back of the pads, where the pistons make contact.  I also put a little on the ends of the pins, but those were the only places I used it.

 

I installed the o-rings dry and then dipped the bottom of the pistons in a little brake fluid, before sliding them in.  Then I blew out the area around the pistons, above the seals, to remove any excess fluid.  I also used brake fluid on a rag to clean the rubber dust boots and dried them off before putting them on.  My thinking is that brake fluid belongs inside the calipers and that it would encourage rust in the outer part of the bore.

 

This was only the second time I have ever had calipers apart.  I learned a lot.  I did reuse the rubber bits, as well as the hardware kit (pins and springs).  If I had it to do over, I would probably have included a couple of sets of seals and o-rings in my piston order.  It was a disappointing feeling opening that box and realizing that for $20 it could have contained brand new rubber.  I went ahead with the assembly and am confident that they will not leak.  I promise to update this thread if they do.

 

Rubber kits are cheap, when you consider the time it takes to thoroughly clean the old bits.  I used a soft rag and brake fluid.  It takes a lot of rubbing to get back to clean rubber.  It is not so much that they seem tired, but just time consuming getting them clean.  

 

As stated at the beginning of this thread, cleaning is such a huge part of automotive maintenance.  I cleaned the bleeder screws using a wire wheel in the drill press.  It is much more gentle than the one on the bench grinder.  The slower speed lets you remove the grime, without completely cutting through the cad plating.  

 

 

I then added anti-seize to the threads, as well as the threads on the flare nuts.  I also put a little between the nut and the brake line, at the end away from the flare.  It is not fun to be loosening a nut and have the line trying to turn with it.  I am a huge fan of anti-seize.  

 

 

The calipers are on and bled and tested, but I still have air in the system and will bleed them some more.

 

 

I added a T fitting to my bleeding set up and used two catch-jars and three wrenches to connect to all three bleeders at once.  That way I could pump up the pressure bleeder and move from upper to outer and inner without having to move stuff around.  It felt pretty civilized.   I am heading up to do that one more time and see if that makes for a firm pedal.  

 

I should mention that I had a helper...

 

 

I think I am getting close to DONE... for now.

 

 

 

[JohnH]

cleaning is such a huge part of automotive maintenance

 

I agree, and is the bit I enjoy most, sad as I am. You can see a result. I'm not into washing and preening (the car) however.

 

The object of using the RRG is to stop rust forming where the seals seat, and in the cylinder bore above the seal and on the piston above the seal. I always grease the lower part of the piston before I insert it into the cylinder. It helps it slip in. No real pressure is needed. Just little jigger side to side and in it slips We are talking ounces of pressure here..

 

I know that you all know this, but its worth explaining again. As the piston extends and presses against the pad the seal deforms slightly. When you lift off the peddle the seal pulls the piston back a tiny amount. It wont do this if rust is stopping it.

 

I like your assistant Minty, its nice having a companion.  

['76mintgrün'02]

I enjoy the cleaning as well.  Cheap fun.

 

I noticed the tiniest bit of wear on one of the inner edges of the rubber o-rings  I did not pay close enough attention while taking them apart to know whether this edge was on the inside, or the outside.

 

I chose to put them back with that edge towards the back of the bore.  I think that is the way they came out.

 

Reusing seals might seem insane, but if you do choose to do it, I found that compressed air aimed right at the o-ring would cause that part of it to be blown out of the groove; allowing a thin smooth tool to be inserted, to lift it the rest of the way out.

 

I read the links you posted for the red grease and it is apparently vegetable based.  Had I known this, I may have put a little Crisco in there

Edited July 11, 2015 by '76Mintgrun'02

['76mintgrün'02]

For the sake of closure, I would like to report that it is all back together and working well.  No leaks.  No dragging!  Stops well.  All in all, it feels successful.  Had I not been a Neanderthal and broken that piston, it would have gone a little smoother, but that turned out to be a cheap lesson.

 

Thanks to all of the participants in this thread.  It is way more fun to share the experience (and learn from yours) than it is to do this stuff all by myself.  

Tom