Simple brake bleeding no longer simple...

[Bufort]

I just bought a nice pair of rearsets for my 2010 796, which also needed a slightly longer brake hose, so whacked it all on, bled it the normal way - useless. The pedal moves all the way and no braking at all. Just to define 'the normal way', so if I'm getting this wrong somebody can point it out, but I've bled many brakes before with no issues: open bleed nipple - push brake pedal - tighten nipple - release brake pedal. Reservoir kept topped up, and no leaks anywhere.

Then I used a syringe and pipe to reverse bleed it - the first 10ml went in easy, then the next 10ml was really hard to force in. So I left it like that assuming/hoping that it had got harder because the system was full and any air that was in there had gone, so tightened it all up. Useless, no difference at all.

I disconnected the main hose from the piston, forced some fluid in through the caliper bleed nipple, just to check that had no blockages, and it came out the open end fine. I then pushed the pedal and fluid came out the opening on the piston, so that appears to be working. The whole thing acts as if theres no fluid in there at all. I checked all the connections and no fluid leaks. I can only assume theres air stuck in the caliper, but that's odd as forcing fluid through the bleed nipple should eradicate that.

What do I try next?

[rollo22]

Sounds like an air pocket it the hose.
It's a real pain but you need to get the Caliper above the brake pedal and try again.

[Bufort]

Sounds like an air pocket it the hose.
It's a real pain but you need to get the Caliper above the brake pedal and try again.

How would the reverse bleeding not have gotten rid of it then?

If I raise the caliper, which way would I bleed it? I assume you raise it to let air bubbles rise up, so normal bleeding?

[BigOz]

Are you certain the piston in the master cylinder is returning all the way? If not it will not be opening the circuit to the reservoir to allow the master to refill, the actuating rod is normally adjustable to set this. This would also stop the reverse bleeding from working.

I also use the technique of pumping the master several times holding the brake on on the last pump then momentarily crack the bleed nipple it seems to work well at pushing air though the system.

[Bufort]

Are you certain the piston in the master cylinder is returning all the way? If not it will not be opening the circuit to the reservoir to allow the master to refill, the actuating rod is normally adjustable to set this. This would also stop the reverse bleeding from working.

I also use the technique of pumping the master several times holding the brake on on the last pump then momentarily crack the bleed nipple it seems to work well at pushing air thought the system.

Well I removed the rubber hood on the rod and can see the piston move in and out when pushed, and then when I had the master cylinder off, the fluid would move in and out of the opening with the movement of the rod.

I tried pumping the pedal a few times when I bled it the normal way, and it didn't seem to make a difference either.


If theres an air pocket in the hose, wouldn't the reverse bleed remove this though? Isn't that the entire point of this method, to force all air out to the top reservoir?

[alan c]

I am having the same problem as fitted rear sets to my M1100.

Did much the same as you, even borrowed a vacuum pump but still no joy !
Just got some red rubber grease as after discussion as think air may be getting through bleed nipple thread ?

Tried to undo rear calliper bolts, one came out ok but other one solid and rounded off snap on allen key socket !!!

Will try grease and try and remove bolt at the weekend, if no joy will have to take to a mechanic.

[BRH]

Hi, I had the same problem, what I do is remove the caliper and release the pipe from under the swingarm, then hang the caliper from a stool or chair, not forgetting to put a spanner between the brake pads and bleed.
It's a right pain but works, good luck.

[Bufort]

Did much the same as you, even borrowed a vacuum pump but still no joy !
Just got some red rubber grease as after discussion as think air may be getting through bleed nipple thread ?

I wouldn't have thought that in my scenario, a minute air leak in the nipple could let in so much air that my brake would go through all its travel and not move the brake pistons at all. If it was working but just a little spongey, I would be at least happy that the laws of physics aren't being bent. But somehow, pushing in more fluid than the entire system can hold, has still left at least a master cylinders' worth of air inside it!

:hissy::confused:

[BigOz]

Well I removed the rubber hood on the rod and can see the piston move in and out when pushed, and then when I had the master cylinder off, the fluid would move in and out of the opening with the movement of the rod.

I tried pumping the pedal a few times when I bled it the normal way, and it didn't seem to make a difference either.


If theres an air pocket in the hose, wouldn't the reverse bleed remove this though? Isn't that the entire point of this method, to force all air out to the top reservoir?

Is there a return spring on the pedal, if not it is relying on the return spring in the master and you should be able to pull the pedal up a little off the return spring pressure in the master.

When you reverse bleed you should be pushing fluid all the way to the reservoir did you see the level change? if not remove the actuating rod completely and try reverse bleeding again.

[Bufort]

Hi, I had the same problem, what I do is remove the caliper and release the pipe from under the swingarm, then hang the caliper from a stool or chair, not forgetting to put a spanner between the brake pads and bleed.
It's a right pain but works, good luck.

Yep, this is what I'm going to be trying tomorrow, I just don't understand how there can still be air in my system!:scratch:

[Bufort]

Is there a return spring on the pedal, if not it is relying on the return spring in the master and you should be able to pull the pedal up a little off the return spring pressure in the master.

When you reverse bleed you should be pushing fluid all the way to the reservoir did you see the level change? if not remove the actuating rod completely and try reverse bleeding again.

Theres no spring on my pedal, but I haven't properly set it up yet so loads of play.

When I reverse bled it, it pushed the reservoir level up, then I took some out, and pumped in some more. So it appeared to do the trick.

[alan c]

Yep, this is what I'm going to be trying tomorrow, I just don't understand how there can still be air in my system!:scratch:


Same as me :Furious::Furious:

[Bufort]

Same as me :Furious::Furious:

I'll let you know how I get on tomorrow.

[Bufort]

Sorted.

I raised the caliper, which could have been the solution, but whilst it was raised I also noticed a miniscule leak where the hose joins the banjo bolt, so tightened that too.

Blockhead, I hung the caliper from my rear subframe, and pumped about 10 times before holding the pedal, releasing bleed nipple, tightening bleed nipple, releasing pedal. Took about 10 goes for it to firm up. Works really well now.

http://s7.postimg.org/i7q0xqru3/Screen_Shot_2015_12_01_at_19_57_48.png

[alan c]

Must be lucky Tuesday !

Sorted my rear brake, looks like it was leaking air from bleed nipple thread, applied red rubber grease, removed piston bolt and reverse bled with vacuum pump, couple of goes and top up of fluid and now all good !

Thanks Oz for info on greasing nipples !!! and thanks to Shuffy for pump !

Also managed to remove damaged calliper bolt and replaced :thumbsup:

[Bufort]

Alan C, hi-five!

Dang, can't believe there's no hi-five smiley.

:woot: :banana:

[alan c]

Cheers Matey :thumbsup: pleased you got sorted as well, I had already spent several times trying to do :scratch:

Looks like you have DPP rear sets same as me !

Where did you get longer brake pipe ? Got mine from Max but it is a tight fit. is yours tight on swinging arm ?

[Darren69]

Bleeding rear brakes are a pain in the rear! Who uses them anyway? :)

[slob]

Who uses them anyway?
MOT testers and race scrutineers
(and Harley'/dirt-bike riders, if you ever ride a Harley' you'll find that the front brake needs about three weeks notice in writing before it will think about stopping you but the back brake is a life saver)


Thanks Oz for info on greasing nipples !!! and thanks to Shuffy for pump !
I can't believe GT hasn't commented on that line...

[alan c]

MOT testers and race scrutineers
(and Harley'/dirt-bike riders, if you ever ride a Harley' you'll find that the front brake needs about three weeks notice in writing before it will think about stopping you but the back brake is a life saver)



I can't believe GT hasn't commented on that line...

I set him up !!

Gary is down in the dungeon (sorry basement) looking for his clamps !

[Bufort]

Looks like you have DPP rear sets same as me !

Where did you get longer brake pipe ? Got mine from Max but it is a tight fit. is yours tight on swinging arm ?

I got it with the rearsets secondhand. It's a Venhill one and fits well, but thats why it's there, because it's longer than standard.

[Nickj]

It's odd because the priller I've got has the same (virtually) up side down rear caliper and it...
(a) bleeds easily
(b) WORKS !!!

Dunno whats going on with it really and I do find having a rear brake that works (other than at MOT time) a bit unsettling :eek:

[Bufort]

It's odd because the priller I've got has the same (virtually) up side down rear caliper and it...
(a) bleeds easily
(b) WORKS !!!

Dunno whats going on with it really and I do find having a rear brake that works (other than at MOT time) a bit unsettling :eek:

This brake works really well now. Why's it unsettling?

[Darren69]

If you're just changing fluid its not usually a problem. Its when you have assembled from 'dry' that you get air pockets trapped. Sometimes it can be in the master cylinder and there's not enough piston travel to push it out. Have you tried bleeding from the banjo bolt on top of the m/cyl?

I've had similar problems with front brake and clutch masters in the past and that usually works, you can hear the air come out.

You will have to cover everything carefully to not spill fluid on your bike of course.

[Bufort]

Umm, the brakes fine now... Have a look at the comments....