Help me find Brembo Leaks (fixed)

[Bpreynolds2]

Continuing the ONGOING work on my Cali Stone project.  I added a 2nd Brembo up front, getting both calipers used from Ed at GP.  Not his fault but ever since getting them they’ve never behaved quite right and I continually seemed to get air in the system from somewhere, even when bleeding them seemed to reveal no air whatsoever.  Since starting the brake work and having the issues, I can see now that I wrongly assumed it was a leak in the master cylinder when it’s kinda obvious now it’s actually somewhere in the calipers.  The other night I did the zip tie thing and the next morning I noticed there were two wet spots on garage floor below both calipers.  I can’t, however, tell where the leaks are coming from per se.  What would you do next?  Banjo bolts and bleeder screws both very tight so can’t imagine it is there but it might be.  I used older, possibly used copper washers so maybe.  But what next?  Throw some powder on calipers and try to locate leak?  Replace/rebuild both calipers’ seals just for good measure?  ???

[Stevex]

Funnily enough I've had the same problem with my original LM2 Brembo calipers.
I had them re coated and I then re sealed them, but they leaked from the piston seals. After re sealing twice more and still not curing the problem
I bit the bullet and bought replacements for the two front calipers. I had thoroughly cleaned and inspected the originals and replaced the pistons with the alloy ones, but could find nothing wrong with them.
The rear caliper seems to be holding fluid now, but the two replacement fronts then also started leaking, again from the pistons; what a thorough pita!
I re sealed both calipers but they continued to leak, all seals so far being original Brembo; finally, late last year I re sealed the calipers yet again with Viton seals.
Lets see what happens,

[blackcat]

I’d rebuild both calipers just so you have a good starting point. Not familiar with this bike but is the master cylinder correct for two calipers?

[Bpreynolds2]

I’d rebuild both calipers just so you have a good starting point. Not familiar with this bike but is the master cylinder correct for two calipers?

Hey BC, thanks for input.  I possibly will rebuild them but because I'm super lazy  I always try and solve problems from the easiest fix first then move on to the next thing.  Mainly posting here to see if there is something in the mix that I'm maybe missing and should check.  Just curious, what would the master cylinder have to do with the leaks on the floor below the calipers?  I mean, yes, the size of the master would definitely influence brake feel but not sure how it would influence leaks?  Unless I'm misunderstanding it, a smaller master would exert more force on the line (I think) and possibly better exploit a leak but my thinking is a leak is a leak? 

[blackcat]

No, a leak is a leak, I was just asking about the MC because the wrong sized one for two calipers will have an impact on braking.

I just went through a whole process of bleeding the brake on my LeMans and the leaks in two calipers were so minimal that the only way I found them was lifting the dust covers on the pistons.  In your case I'd just buy two kits and be done with that likely problem.

[Bpreynolds2]

No, a leak is a leak, I was just asking about the MC because the wrong sized one for two calipers will have an impact on braking.

I just went through a whole process of bleeding the brake on my LeMans and the leaks in two calipers were so minimal that the only way I found them was lifting the dust covers on the pistons.  In your case I'd just buy two kits and be done with that likely problem.

Good deal and much appreciated.  I think I'm still holding out hope there is something simple in the works like re-used banjo bolt washers.  But as of yet I have not inspected beyond just the naked eye glance this morning and I couldn't detect where exactly the leaks are originating.  Btw, I hate running down leaks.  I just went through this whole thing myself where gas on the project bike was coming from the bolt holding on the low fuel sensor on the gas tank.  No wait, it was the sensor itself.  Wrong again, I was  Then I thought it was a leak in the seam of the tank.  Finally, the leak was actually coming from the drain bolt on the OTHER side of the tank.   

[80CX100]

     I've never split a Brembo caliper apart to rebuild them, but when I researched the pros/cons of rebuild/replace, I read a few posts of owners that despite their best efforts using Brembo O rings/seals ? had internal leaks between the 2 caliper halves, hidden out of sight  that they were never able to get to seal properly once split.

     fwiw ymmv

[John Croucher]

When You added the second caliper did you change the master cylinder to a larger piston size?  If you used the original m.c., the brakes will feel mushy and like they have air in the system.  No amount of bleeding will get rid of the mushy brakes. 

[Bpreynolds2]

Hey all, I certainly appreciate the input here about the master cylinder info; however, I am mainly concerned at the moment about both calipers leaking and either using various methods to find/fix the leaks or just rebuilding the calipers with new seals and such. 

[Stevex]

There are not actually many places they can leak from. Start by removing the piston dust seals; if the piston seals are the culprit, the dust seal inners will be covered in brake fluid. If they're ok, it's a choice between, the banjo bolt copper washers, bleed nipple or caliper halves seal; any of these should be fairly obvious, especaily if you've removed the pads for better visual access.
Did you really re use old copper washers?, if they weren't re heat treated they could well be where your problem lies.

[Bpreynolds2]

There are not actually many places they can leak from. Start by removing the piston dust seals; if the piston seals are the culprit, the dust seal inners will be covered in brake fluid. If they're ok, it's a choice between, the banjo bolt copper washers, bleed nipple or caliper halves seal; any of these should be fairly obvious, especaily if you've removed the pads for better visual access.
Did you really re use old copper washers?, if they weren't re heat treated they could well be where your problem lies.

Good info and thanks, Steve. 

[Scout63]

It’s easy to displace the little o-ring between the caliper halves when assembling. I usually just buy a seal kit, and if the pistons are cruddy, get new ones.  Sadly, it’s almost better to buy replacement calipers from MG Cycle (if they are F08’s).  When you add up the cost of parts and the fact that the new ones have a shiny finish and come with new pistons, seals, pins and pads, it’s kind of a no brainer.

[blackcat]

It’s easy to displace the little o-ring between the caliper halves when assembling. I usually just buy a seal kit, and if the pistons are cruddy, get new ones.  Sadly, it’s almost better to buy replacement calipers from MG Cycle (if they are F08’s).  When you add up the cost of parts and the fact that the new ones have a shiny finish and come with new pistons, seals, pins and pads, it’s kind of a no brainer.

I wanted to keep the dual bleeders on the Lemans so I was resigned to buying used ones on eBay or I would have bought new replacements. Yes, they were a pain to get sorted as I ended up buying three rebuild kits for two calipers but they don’t leak now.

[Bpreynolds2]

If I knew what I know now, I would certainly have just purchased the new calipers for sure.  Prior to this project, I had never done any brake work besides fluid replacement, bleeding, etc.  About the only thing keeping me from buying new ones now is that I've already spent money on the used ones and such.  While I nearly always seem to take the long, hard road in the garage with any project, it would be smart of me to forget this small change on the used calipers, bite the bullet, and just get the new ones.  While I do a ton of wrenching, seemingly, I'm not one of those guys who actually enjoys it so much - see my post on the current "Isn't wrenching great" thread heh.  Getting the new ones would certainly save me some teeth grinding, headache, and uncertainty (no guarantees I'll install the kit correctly nor what I'll find when I get in there - pistons might need replacing, etc., etc.).  We'll see.

[Antietam Classic Cycle]

"Cal Stone project" - so four piston calipers then? A bit more difficult to find rebuild kits for.

[MattP]

get a 8oz  of 3m silicone paste part no-08946  pull out seals clean up ect apply  this stuff . I have used on calipers that leaked and or hung up  worked every time for me on realy crappy ones also. I think it is the same stuff you usted  to get in that little plastic squize thing with rebuild kits.Matt

[Bpreynolds2]

"Cal Stone project" - so four piston calipers then? A bit more difficult to find rebuild kits for.

Unless I'm looking at the wrong thing, I found it somewhat quickly on Ebay and maybe a few other suppliers - not available from MGC - just googled "rebuild kit p4 brembo 65mm".  https://www.ebay.com/itm/152344615107

From most distributors about $90 plus shipping and includes kit for 2 calipers for the $90.  Does not include new pistons. 
New calipers from MG and other sources about $215 per caliper.  If the time, energy, patience, capability is there you can save several hundred dollars doing this but it won't be nearly as easy nor nearly as nice as the new calipers.  But again, we'll see.  Haven't made my mind up yet.  Tonight I'm going to go back over the leaking calipers I have now to see if I can possibly determine the source.  I'm suspicious, maybe hopeful, the leaks might be at the washers/banjos only.

[Canuck750]

I have rebuilt quite a few and have had the same problem you have noted.

A couple things, make sure you have matched pairs of caliper bodies, second glue a piece of 240 wet/dry sandpaper to a piece of glass and sand the mating surfaces flat applying pressure on the caliper while rotating and spinning the caliper body on the sandpaper.

Use a new tiny O ring for the fluid passage seal between the caliper bodies. Check the surface of the caliper piston recess are spotless, no burrs where the flat O ring piston seal rides. I assume you are fitting new piston seals, the fluid and the dust seals and your pistons are in great shape or new.



They can be a pain to get right but keep at it.

Jim

[Antietam Classic Cycle]

Unless I'm looking at the wrong thing, I found it somewhat quickly on Ebay and maybe a few other suppliers - not available from MGC - just googled "rebuild kit p4 brembo".  https://www.ebay.com/itm/152344615107

From most distributors about $90 plus shipping and includes kit for 2 calipers for the $90.  Does not include new pistons. 
New calipers from MG and other sources about $215 per caliper.  If the time, energy, patience, capability is there you can save several hundred dollars doing this but it won't be nearly as easy nor nearly as nice as the new calipers.  But again, we'll see.  Haven't made my mind up yet.  Tonight I'm going to go back over the leaking calipers I have now to see if I can possibly determine the source.  I'm suspicious, maybe hopeful, the leaks might be at the washers/banjos only.

  That's the only source for a kit that I've found, couldn't remember the name.

[Bpreynolds2]

Thanks, Cannuck and ACC!

[Bpreynolds2]

No one is/was asking for it but updating this thread to say the issue is resolved.  The “leak” was likely the re-used copper washers at the banjo bolts/calipers.  Having said this, I also went ahead and replaced the master cylinder with a 15mm (up from the 13mm I had used).  So the washers fixed the leak and the 15mm master fixed the spongy feel.  All good and thanks for the advice. 

[Antietam Classic Cycle]

 

[bikeridertim]

+1. 👍🏻

[Canuck750]

No one is/was asking for it but updating this thread to say the issue is resolved.  The “leak” was likely the re-used copper washers at the banjo bolts/calipers.  Having said this, I also went ahead and replaced the master cylinder with a 15mm (up from the 13mm I had installed.  So the washers fixed the leak and the 15mm master fixed the spongy feel.  All good and thanks for the advice.

Excellent! Glad you got it fixed.