24 replies to this topic

[gozer]

I`ve stripped, reprayed and rebuilt the master cylinder and all seems to be working ok but the brakes are still dragging too much to pass an mot. I guess it`s gonna have to be a caliper rebuild next  . Will the pistons have enough room to come out without having to split the calipers??

Also, if they are split, do I need specific O rings for the  crossovers, or are generic O rings ok?

Edited by gozer, 28 January 2023 - 02:41 pm.

[SirRealEd]

I`ve stripped, reprayed and rebuilt the master cylinder and all seems to be working ok but the brakes are still dragging too much to pass an mot. I guess it`s gonna have to be a caliper rebuild next  . Will the pistons have enough room to come out without having to split the calipers??

Also, if they are split, do I need specific O rings for the  crossovers, or are generic O rings ok?

 

Do you still have the original rubber brake lines?  Sometimes they can deteriorate and act like check valves prevent fluid from getting back to the master cylinder freely.

 

I've had pretty good luck with removing the pads and pumping the pistons out a little bit and cleaning up the pistons with a soft brush and adding a little rubber lubricant to the seals, then pushing the piston back into the caliper.  Do this a couple times and it might free up nicely.

 

If you know the seal dimensions, you might find seals from an industrial source.  Chemical compatibility is a factor.  You might have to buy in bulk.  Might be cheaper and easier to use OEM seals.  Flush your brakes annually and you might be good for 20 years.

[dapleb]

If ewe search powerhouse it'll find ewe a thread with lots of info. They do noice piston and seal kits including calipot arf seals

[dablik]

Yup pistons will come out okay, generic O'rings no good, caliper pot ones are more flat in profile, loike a rubber band.

[leehenty]

Caliper seals have a square or rectangular profile

[gozer]

 

Do you still have the original rubber brake lines?  Sometimes they can deteriorate and act like check valves prevent fluid from getting back to the master cylinder freely.

 

I've had pretty good luck with removing the pads and pumping the pistons out a little bit and cleaning up the pistons with a soft brush and adding a little rubber lubricant to the seals, then pushing the piston back into the caliper.  Do this a couple times and it might free up nicely.

 

 

Yes, still got OE hoses but the flow seems good back to the master cylinder when I push the pistons back. I`ve had the pistons in and out more times than a fiddlers elbow and cleaned them each time. It seems that three out of the eight are a bit  more sluggish to return so probably a build up of muck between the dust seal and the piston seal causing the issue is my guess. More unexpected arsing about it is then

 

Yup pistons will come out okay, generic O'rings no good, caliper pot ones are more flat in profile, loike a rubber band.

 

Caliper seals have a square or rectangular profile

Thanks for clarification chaps

[gozer]

I can`t for love nor money get the pistons out of the calipers so I`ll have to split them. Not had to split a caliper before so when I put the two halves back together, is there a recommended torque for the joining bolts? I don`t see one anywhere in the manual, or is it just a case of wind them in until they stop and then nip them up a quarter turn?

I don`t wanna find out I`ve done summat wrong as I`m approaching a bus/lamp post/brick wall at a rate of knots!!! 

[dapleb]

Thread on ear talks abooot getting pistons ooot and torquing arfs. Search "pistoons".

[Catteeclan]

Must be well tight if you can"t get them out with brake lever.

[Favs]

Just had a look in the shed and woohoo  left over from when I swapped to blue spots -  I have both standard front calipers from my Mk2A and the hoses and they have the original black plastic caps over the pads too. Just in case it all goes belly up Now you know this - all will go fine  

 

Also is present Mk1 headlight glass/lense + gear lever.- I think I'll have a proper looksee tomorrow for owtelze

[Snowbird]

I also have a full front mk2a front stopperiser system in my shed so spares are available if it all goes tits up.
So you should be fine, the curse is broken.

[gozer]

This brake fixing lark is more of a turdfest than it ought to be. I got the left one on the bench as I couldn`t get the pistons out far enough with the lever and I tried a pair of those piston pliers that go inside the piston, about as much use as a chocolate teapot! Caliper split, a big wodge of inner tube and a substantial pair of pliers, and with a fair bit of tugging and swearing, the outer pistons came out. The inners were a different matter. No amount of pushing, pulling, twisting or screaming C@#T at them worked so off to beg the use of a big compressor it was. With about 140 psi squirted in through the bleed nipple hole they eventually came out, very sssslllloooowwwwllllyyyy ! After a lot of faffing blocking holes and about 10 mins of big psi, there was a couple of loud pops and they were out.

Now the strange thing is that it all looks ok. No piston damage and the bores are unmarked. The only iffy bits are in the grooves. There is a lot of crud in the dust seal groove which is pretty resistant to scraping with a pick, and there is what looks like a lot of crystalised brake fluid in the seal groove, but certainly nothing that looks like it should have made them so feckin` hard to remove! Question, is it worth soaking them in brake cleaner / acetone / petrol / bleach or other random liquids to try and soften the crud in the seal groove or is it a case of mega patience and careful scraping to get them clean? I hope the other one is less of a bast. As I`ve gone this far I don`t want to let the bastards beat me!!!

 

 

Just had a look in the shed and woohoo  left over from when I swapped to blue spots -  I have both standard front calipers from my Mk2A and the hoses and they have the original black plastic caps over the pads too. Just in case it all goes belly up Now you know this - all will go fine

 

Also is present Mk1 headlight glass/lense + gear lever.- I think I'll have a proper looksee tomorrow for owtelze

 

I also have a full front mk2a front stopperiser system in my shed so spares are available if it all goes tits up.
So you should be fine, the curse is broken.

Thank you chaps, at least I know I have an exit strategy before I get to insanity and use of a sledge hammer!

[Catteeclan]

I've always scraped it out. Seems a bit butcherist while all the lumps are falling out but does the job.
Be interested to hear if anyone has a better way too. 

[Snowbird]

A belt sander and bits of old hacksaw blade can make some very handy shaped scrapers for groove cleaning.

[curlylegend]

A belt sander and bits of old hacksaw blade can make some very handy shaped scrapers for groove cleaning.

 Any kind of Dremel tool and a selection of rotary wire wheels usually do the trick.

[dablik]

I'm with curly, done them quite a number of times, dremel makes it easy, these and Bluespots need regular attention and they work lubberly... good luck, half way their 

[Favs]

Living on a prayer ... ooohhh aaahh

[dablik]

Living on a prayer ... ooohhh aaahh

[gozer]

The right hand side was half as sticky again as the left with no obvious reason but all done now. There is still a bit more of a spongy feel at the lever than I would like but that`s most likely the OE hoses so braided lines are on the list,

 

 Any kind of Dremel tool and a selection of rotary wire wheels usually do the trick.

 

I'm with curly, done them quite a number of times, dremel makes it easy, these and Bluespots need regular attention and they work lubberly... good luck, half way their 

I went down the dremel route and it worked a treat so thanks for the tip guys. 

Onward to the next disaster now1

[jamy]

Hope it isn't an issue reviving this thread as I am about to service the front brakes on my TDM 900A.

 

I have no real worries about undertaking the work, my only issue is: how do I avoid getting air in the lines, and subsequently ABS system, when removing the calipers?

 

Any advice and tips would be more than welcome.

 

James.