Rebuilt the calipers, now they leak!

[psyguy]

ok, so i disasembled everything to the very last bit, front and rear brakes.

cleaned all out, polished, powdercoated, lubed, put new m/c kit in, new ss lines, etc, etc.

the seals and pistons seemed all right (very minor pitting on pistons, rubber parts all pliable and flexible and not damaged), so i reused them.

the back brake is all ok

but both front calipers leak...

what gives?

thanks for your thoughts fellas

[silverhorse47]

Could you have put the cones in backwards? The lip faces in. It's also pretty easy to nick the seal on the cone when you press the piston back into the bore. I imagine you put the same pistons and seals back in the same cylinders? Hope you get it sorted, that's a drag.
S.

[psyguy]

i didnt pay particular attention to matching the caliper/seal/piston but dont think that could be the issue cos when you buy a new rebuild kit you get a new setup anyway, i guess?

not sure what "cones" you're referring to?

[Matchless]

i didnt pay particular attention to matching the caliper/seal/piston but dont think that could be the issue cos when you buy a new rebuild kit you get a new setup anyway, i guess?

not sure what "cones" you're referring to?

psyguy,
I found the grooves that take the square rubber ring in the caliper bore was caked with corrosion under the old rubbers. It was quite hard getting it clean and keeping the metal smooth. I also used red rubber grease under the seal in the groove. Your pistons (if you reused the old ones) must not have any pitting in the travel area where the metal meets the rubber. Just for info, you can use the aftermarket rubber kits for the BMW316I which also use 38mm seals and are exactly the same excluding the boots of course.
Keep well.

[silverhorse47]

"the seals and pistons seemed all right (very minor pitting on pistons, rubber parts all pliable and flexible and not damaged), so i reused them"

Sorry, I thought you said you reused the rubber bits on the calipers, and put a kit in the master. I imagine that what I call 'cones' are what Matchless calls the "square rubber ring".
Regards same pistons in same holes, my opinion is that generally it's best to keep parts matched on reassembly, especially if reusing. They wear together. Matchless is right about dirt, cleanliness is next to godliness with brake bits...they are very sensitive to any dirt scoring or pitting.
S.

[psyguy]

psyguy,
I also used red rubber grease under the seal in the groove.

matchless,
i got the grooves very clean using a dremel tool and a round brush - worked a treat...
now, what exactly is the "red rubber grease" ?
i used only the brake fluid to lubricate the seal and the piston.

the problem i guess is that i dont know if the leak might be coming through inbetween the rubber seal and the caliper, or the rubber seal and the piston, or possibly both...

[Suzuki mad]

PSguy, I don't see in your post that you have stated where the callipers are leaking.

So idea's are...

Its not the powder coating thats causing the leak? The coat will be thicker than the original Suzuki paint. (Powder coat in the seal groves?)

You changed the crush washers on the banjo's?

Seals are in correct groves and one hasn't popped out while fitting the piston.

In theory what you've done they shouldn't leak. It was the right set for the callipers and bike as a silly thought.

[Matchless]

Have look here post 11 http://www.thegsresources.com/_forum...=rubber+grease

Usually brakefluid works well.

[Nessism]

Using grease to lubricate brake seals is a no-no, brake fluid is the only material allowed inside the sealed brake system.

Sounds like you need to get a new set of seals. Using a dremmel to wheel out corrosion might have taken off some of the caliper material (hopefully, not too much). I'd start fresh with new seals and if the pistons are pitted, even a little bit, I'd replace them.

Good luck,

[bwringer]

The seal kits from Suzuki are high quality, easily available, reasonably priced and include new pistons.

The aftermarket kits are expensive crap and don't include pistons.

If I'm reading you correctly, it sounds like you re-used the old seals. That's never going to work.

[psyguy]

PSguy, I don't see in your post that you have stated where the callipers are leaking.

at the piston/seals area

powdercoating wouldnt be a problem, cos the calipers were all nicely masked and all

[psyguy]

Using a dremmel to wheel out corrosion might have taken off some of the caliper material (hopefully, not too much).

yea, this is my big worry too, but it was the only way to get rid of all the dirt and get a reasonably smooth grove surface...

[psyguy]

it sounds like i need to order a kit (piston/seal) from suzuki and try that first...

hopefully that'll do the trick...

but bloody shipping prices to new zealand are killing me (and it's even more expensive to order it through the local stealership!)

[psyguy]

so, the brake rebuild kits from suzuki arrived and i chucked them into the calipers...

i'm yet to test the brakes but i'm not too hopeful (at least for one of the calipers) - as i squeze the lever the caliper gives a funny sound as if leaking/drawing fluid/air (at the piston/seal area)

the seal grooves are all nicely clean and shiny so i'm at a loss as to what might be the problem - unless as suggested, the dremel i used to clean the grooves took away some caliper material

[almarconi]

How difficult was it to insert the piston into the bore?

Mine was so tight I had to use a c-clamp to press them in. Some people claim they can insert the piston by hand but I could not. It was the same on the front pistons and the rear. The dust seal tears easily, on mine if I didn't get it right the first time the seal was history.

Are you sure the dealer sold you the right pistons/seals for your caliper?