The situation is.
Shimano XT brakes (the type with the shiny XT top cap and ‘easy to bleed’)
I store my bike front wheel up on the wall
I’ve had some issues with the brakes being really spongy so I had a go at bleeding them, they seems ok for a handful of rides then hung up for a couple of weeks got it down for a ride and no rear brake at all.
LBS bled it for me
Seemed fine for a dozen rides
Hung it up for last 4 weeks (been riding hard tail)
Got it down tonight at I want to ride it tomorrow and guess what……..No back brake at all. You can pull the lever and wheel the bike along no problem.
Iv’e flicked the lever a few times and it is no better so…..
Got the bleed stuff out the tool box, syringe on the lever housing, syringe on the bleed nipple on the caliper,, both with fluid in.
Cracked open the nipple and tried to push some fluid up to the lever, no go, wound the nipple out a bit more just incase i hadn’t cracked it open enough, nope still not working so I tried it the other way from the lever down, nothing, no fluid transfer at all.
I was pushing gently on the lever syringe and noticed fluid weeping out between the silver top cap and the black lever body I’m hoping this is normal as i suspect it is just a reservoir under no pressure so does not have a pressure resistant seal – tell me if I’m wrong.
Its almost like the hose is crimped but it does not seem to be (otherwise the lever would be firm)
Has something gone wrong inside my lever housing?
Is it f8cked!?
Any help would be great
I’m not a monkey when it comes to mechanical things but these brakes are getting on my tits now!

Have you got the bite adjustment screw wound in? If so, unwind it.

Also how old are the brakes?

When you bled the rear brake did you do it with the brake still on the bike? If so take it off and let it hang vertically – air bubbles can get trapped and doing the bleed in the “normal” position doesn’t get rid of it.

Bite adjustment meaning free stroke screw?
They are 3 years old

I’ve had fluid weep from the lever cap before. It’s fine.

I think that if you bleed with two syringes, you need to gently pull one while pushing the other, otherwise it can be hard to overcome the plunger.

If you’ve not got the funnel, try taking the plunger out of the top syringe so that it’s just a reservoir.

To be honest it does sound like something else is happening if the shop couldn’t sort it either.

Try removing the hose and then forcing some fluid through the caliper and lever to check it’s not a blockage in one of those.

Yes, the free stroke screw on the brake lever.

Is there any oil leaking from around the calipers?

As kayak says – the upper syringe just needs to be a reservoir/container.

I think that the weeping seal in the lever is the issue. I had the same symptoms, including the fluid weeping from the seal – went through the same heart ache you are going through and it was only resolved with a new lever (you can’t get seal kits, a new lever is only about £30 odd from CRC). That was 3 years ago, no problems since!

initially the upper one was just a reservoir and i’ve had it before where you crack off the caliper bleed nipple and you can see the fluid come out under gravity, but not this time so I gave it a little help with the plunger but still no good.
I’ll check on the free stroke screw in a minute.
Thanks

Hi. I’m a bit confused! 2 syringes? Have you got the yellow pot like thing that screws into the brake lever reservoir? The calliper should be off and pads out, bleed nipple ? turn,syringe tube on nipple, top screw on lever reservoir off yellow pot screwed on , push in syringe ,a fair amount of pressure needed. Fluid will go into pot when no bubbles job done, assuming your completely bleeding system with fresh fluid. I got a new set of XT785 as didn’t trust m8000, long story short , got sent brake system in component form all needed a complete bleed. Done as above , no leaks no probs.how long you had yours? On my hardtail the 785s are almost 2 year old ,I cut down hoses when fitting and have never bled them and their just as when I installed them.

Run through this and also go through the comments at the end – there’s a few with similar problems to yours.

Free stroke screw was about half way in

Clamp brake lever shut and leave overnight…ideally with levers at highest point with brake hose as vertical as possible.

In morning remove clamping solution and brake will feel sharp…the air is now at the reservoir…remove top cap and top up…removing the air. Repeat that a few times and should be sorted.

DickBarton………………Watch this space, I’ll report back in the morning lol
Although that doesn’t explain why i can’t get any fluid through from the bleed port to the nipple..

sounds to me like a failed master cylinder seal that has blocked the port.

Ah, I hadn’t read the full script…I’ve no idea either…however, this may help determine if there is definitely air in the system (also check the caliper for any fluid – in case it is a failed seal and it starts leaking with the constant force of the lever being applied).

I normally tie the lever off and then over 2 hours give the brake hoses a wiggle…it helps move any air upwards…the air will naturally move upwards, but the wiggling speeds it up…

Similar thoughts to TJ, I suspect the master cylinder piston has stuck, and is masking the transfer port from the reservoir so no fluid can pass between them. Short term, you may be able to move it back by removing the hose and prodding inside, long term, you’re probably going to need a new lever.

Well Dickbarton, it’s no better this morning, I suspect something more serious has occurred…..

Can’t help, but had a similar problem in the Alps a couple of years back. Had an XT rear brake and every time the bike was hung on the back of a bus or trailer by the front wheel the rear brake would disappear completely. It usually took about 20 pumps to bring it back to full feel and then it would be fine all day riding. Until the next time it was hung up and shaken! Never did get to bottom of it but it never failed to pump up either. Changed to Zee brakes on return so no longer an issue

OOH, what’s the science behind taping the lever to the bar overnight??
With the lever pulled all the way in, the reservoir in teh lever is closed off to the system..
The only thing I can think is that with the lever pulled in, the fluid is under more pressure, the bubbles are compressed and ‘smaller’, and can creep up the hose a bit more easily..

I suppose once you release the lever the system is open again, so teh bubbles can escape?

am I missing something?

DrP

I think that’s the theory.

It has worked for me in the past.

It would appear that some shimano brakes are just fubarred from birth.

what’s the science behind taping the lever to the bar overnight

My understanding is it allows the air bubbles to rise up and into the highest point (the reservoir) slowly overnight so it is easier to bleed the next morning.

+1 for stuck master cylinder.
The cam system the Shimano levers use only push on the master cylinder, pulling on the lever will not make it return. If like mine it became gunked up, it would not open past the reservoir port.

As above, if you’re going to not use bike for a while store with the brake levers pulled in (I use those charity rubber wrist bands, which are also really good for putting round rim of metal mugs to not burn lips).

Idea being that places pressure non system and any air bubbles should be forced to reservoir as you store it.

Sorry, that has always worked for me.

Unsure of the science but I think the added pressure does encourage the air to move…once up at the reservoir is stops the piston from going spongey…releasing the lever then moves the air into the reservoir and it can then be removed.

I think the tying the lever back to the bar thing works because it resets sticky pistons where people are mistaking sticky pistons giving long lever travel for air in the system. Not sure tho and it has also worked for me

I’m just interested that’s all!

WE’re talking about trying to remove compressible air in a fluid based system.. i’m unclear how pulling the lever back makes the bubbles migrate to the lever end, when clearly hanging the bike by the front wheel (or probably at a 45 degree angle) would do this (for the rear wheel)…

If you wanted to really get the bubbles up, you’d have the system under a vacuum (a bit like pulling the plunger on the syringe when you rill it (with the syringe blocked off) so that the bubbles get BIGGER and rise quicker…)

will hunt for science on the net…

DrP

So far it seems to be the act of releasing the lever, after bubbles have risen, ‘sucks’ the bubbles into the reservoir…

Will keep reading!

DrP

Don’t know why exactly it works, but I’ve found keeping the lever compressed helps