I’ve got a Shimano SLX Brake that is leaking from the Lever cap(rectangular reservoir cap) ,well its blowing bubbles from there when you push the pistons back underwater, so is pretty useless at stopping the bike. Anyway ,does anyone know where you can get the rubber diaphrams that go under the cap/lid from? I’m not holding out much hope as i know about shimano’s great brake spare availability….Doesn’t seem a great idea spending £40 on a new lever that could very easily go wrong again

Thanks in Advance

Top cap and rubber bit (for Saints at least) is available through Madison (via your LBS)

That’s an open reservoir. Just sounds like it needs bleeding and topping up.

That’s an open reservoir. Just sounds like it needs bleeding and topping up.

Been Bled several times, works perfectly first couple of lever pulls, then back to sponge

Some brakes are designed to allow air to escape between the outer side of the diaphragm and the outside of the lever.

Been Bled several times, works perfectly first couple of lever pulls, then back to sponge

Then you’ve got a leak somewhere.

Perfectly normal for air to escape from above the diaphragm as it expands and contracts with fluid displacement. If it was leaking then you’d have fluid, not air, coming out.

obviously i don’t know the full history/condition of your brakes, but i’d expect to see air bubbles from the top cap if i pushed the pistons back in with the lever under water.

if you look closely you’ll find/see a small hole – it’s there to allow air to move in above the diaphragm – to compensate for the diaphragm being pulled down as the pistons extend.

it does sound like you’ve got a problem, but this isn’t it…

who bled your brakes and are they any good at it? (no offence) – if you’re in sheffield i will do it for beer and cake.

As above ! – bet your piston seals are weeping. – shimano feckibg suck that thy don’t supply that !

Thanks for the replies , Learn something new every day!

I’ve bled them , i’ve tried multiple methods from syringe upwards, a bottle, pulling lever and open close bleed nipple and bleed nipple closed and pulling the lever repeatedly to bring up the bubbles,

I’ve had it air free several times, as i said it’d work perfectly for the first couple of pulls ,but then back to mush.

When i was cleaning them up with the compressor some fluid did splatter when i sprayed in to the lever pivot area(but after bleeding so could easily be overflow) piston seals dont seam to be weeping as the pads didnt have any oil on them but who knows!

why are you cleaning with a compressor?

to dry up/clear the crap out of the hard to reach places

Ive just posted about the rubber band on the brake lever technique and this might be apropriate.
When you bleed you might be flexing the master cylinder seal into a good shape which then gradually deteriorates and lets fluid past.

Doesn’t help much, I am afraid, as I doubt the seals are available – like everything else in the Shimano brake section of their catalogue.

spock – Member
to dry up/clear the crap out of the hard to reach places

POSTED 43 MINUTES AGO # REPORT-POST

is that REALLY necessary tho?

racing_ralph – Member

spock – Member
to dry up/clear the crap out of the hard to reach places

POSTED 43 MINUTES AGO # REPORT-POST

is that REALLY necessary tho?

To clean up the brake of water and oil to check for leaks, or are you just being a knob?

No just curious as to why water is an issue in a pivot thats all. How does it check for leaks?

BTW less of the puerile put downs – makes you look like a 15 year old who has just been beaten by his mate on COD

i dont think you understand me, i was cleaning out the brake of mineral oil after bleeding so i could check for leaks without any red herrings.

To be fair, you didn’t come across very well

To be fair, you didn’t come across very well

Touché! And if you both need handbags, ask The Southern Yeti for a supply.

My bet would be either a leak at the piston seals, or somewhere inside the lever: not the diaphragm cap (brakes should work perfectly with the cap off).

I’ve tested for caliper leaks by burning the pads over a gas flame: any oil that’s leaked out will stick to the pads and burn off with white smoke. Burn them clean then put them back in use them a bit then take out and burn again: if white smoke then you’ve blown a caliper piston seal: new caliper time.

If no evidence of a leak at the piston then either a leak in the lever or a dodgy hose-caliper or hose lever seal. You shortened the hose recently?

hold on ,

is it the rear brake ? are you bleeding it on the bike ?

thanks for the replies,

I’ve tried bleeding both on and now off the bike(swapped the brake for a spare one), Yes it is a rear brake but i haven’t shortened the hose.

Interested methods DeeW! Will have an experiment tommorow.

sorry forgot to add, the brake did have a crash a while ago, bent the lever quite badly in the process ,could have affected it? (it’s a freinds brake btw)

I think the problem arose (loss of power) while away in a hotter climate, could boiling the fluid a bit cause a seal to go? I’m not talking alp downhilling but i reckon it could boil the fluid of a long downhill track in Mollorca? What are shimano seals like when it oil get a bit toasty?

spock i hate to say it but both my brakes suffered the same issue after boiling the fluid coming down the north face path of ben nevis – might well be scrap

one last attempt …

fit brake to bike , adjust bike in the stand so the bleed nipple is vertical

rotate lever to the horizontal

bleed from the top down

if this doesnt work i reckon you have weaping seals in the caliper from the heat !

Thanks a lot Trail Rat, Been a bugger to diagnose this one, Will try out DeeW’s methods and give your last ditch method a try.

Thanks,
Sam

Good video on Pinkbike about bleeding Shimano brakes. I know you have tried this might be it might still be worth a watch.
http://www.pinkbike.com/video/170853/