Brembo P08 caliper leak...a question (more leaks!).

[Stevex]

With just a few hundred miles on the LM2 after an overhaul which included an all caliper re seal the right front caliper piston seals are leaking.
Total luck I even found them, as I decided to take out the pads to de grease them as the disc looked a bit dirty.
I know this may sound stupid, but are the piston seals that sit in the caliper, orientated or not?
When I rebuilt the calipers I presumed they were just square section seals which would fit either way round.
The other 2 calipers I rebuilt are fine...oh, and the leaking caliper has the alloy pistons in it.

[ibis1]

The seal should go in either way. I assume you lubricated the seals and pistons during installation and the pistons are not pitted or scored. The only thing you can do is start over and check for any nicks or debris in the seal area. Make sure the pistons are level (Square) when installing them in the bores. Good luck. :BEER:

[mtiberio]

check to make sure the caliper halves are bolted tightly together

[canuck750]

Is the O ring properly seated?



The flat faced seal is non directional. I flatten the two halves of the caliper on  piece of granite with a sheet of 400 sand paper glues to it.



The outer seal needs to be pressed right down to seat into the groove



I lube the pistons with the grease Brembo provides and makes sure the pistons move freely in and out



I use blue locktite and torque the joining bolts to 18 ft. lbs

[rodekyll]

Nice writeup.   ;-T

[Perazzimx14]

Did you clean out the area really good where the flat seal sets? When rebuilding mine there was lots of mineral buildup that needed to be carefully scraped away.

[dilligaf]

Did you clean out the area really good where the flat seal sets? When rebuilding mine there was lots of mineral buildup that needed to be carefully scraped away.

 ;-T  That was my first thought as soon as I read post.  :BEER:
Matt

[ibis1]

canuck lost his calling. He should be working for the service manual people. Nice work!  :BEER:

[Stevex]

Thanks for all the info, I did everything that you've suggested which is why I'm surprised they've gone so quickly, especially both pistons.
Actually the dust seals did a damn good job of preventing the fluid going everywhere and it wasn't until I removed them that the leak on both sides was  fully apparent. I'll re strip and seal once the seal kit arrives.

[Late to the party]

Nice writeup.   ;-T

Canuck 750 does an outstanding job with his documentation.

Nothing is left to doubt... save for our sanity.

Lateness.

[Stevex]

Before ordering a seal kit I decided to pull the other 2 calipers and remove the dust seals to check any problems.
Outwardly everything looked normal, but on removing the dust seals, 3 out of the 4 piston seals are also leaking.
The only thing they have in common is the brake fluid.
I'm using Universal Brake and Clutch fluid Dot 4 exceeding SAE J 1703, which the LM2 user manual recommends.
Honestly can't understand whats going on here.

[rodekyll]

If the pistons or bores are clapped out they will leak

[Stevex]

If the pistons or bores are clapped out they will leak

Pistons and caliper bore of the one caliper I've had apart so far look absolutely OK, anodised finish all there with no signs of wear.

[canuck750]

Are you fitting genuine replacement Brembo anodized pistons, piston seals and dust seals? If the leak is coming from the pistons and the pistons and seals are new then the caliper body must be deformed or pitted allowing fluid to leak past the main seal.

I have found that the caliper casting collects some fine crud behind the piston seal, I used a fine dental pick to gently scrape the circumference of the recess to get the castings as clean as possible, then I cleaned the castings in an ultrasonic cleaner but I think a good hand scrubbing with a stiff tooth brush would work just fine.

Remove the brake fluid seal and perhaps use a magnifying glass to examine the casting recess , the casting should be spotless and have no marks or obvious damage.



Dumb question but are you sure that the service parts are for the P8 calipers and not some other Brembo model?

[Stevex]

Well, with the Guzzi off the road for winter I've checked the resealed front calipers.
Outwardly no signs of leaking but on removing the dust seals, all 4 pistons / seals have let by a small amount of brake fluid.
After 2 full re seals carried out in clinically clean conditions I'm resigned to replacing the calipers.
To belatedly answer your question canuck, yes I'm using the correct genuine Brembo seal kits.

[Antietam Classic Cycle]

Well, with the Guzzi off the road for winter I've checked the resealed front calipers.
Outwardly no signs of leaking but on removing the dust seals, all 4 pistons / seals have let by a small amount of brake fluid.
After 2 full re seals carried out in clinically clean conditions I'm resigned to replacing the calipers.
To belatedly answer your question canuck, yes I'm using the correct genuine Brembo seal kits.

If the calipers had the original chrome plated pistons in them and the plating was flaking at all, chances are that the bore of the caliper body was very minutely scratched when the old piston was removed. Once that happens, the caliper half is scrap. I'm sure someone will be along to tell us how he machined his own oversized pistons and bored the caliper bodies, but to me it's just not worth the effort when a new caliper costs $125. That is unless you're building a 100 point concours restoration.