Bleeding rear brake air lock

[rebelfido]

Hi all I made a rookie mistake on my ST1100 and while bleeding the rear brakes I was only watching the front master cylinder not the rear one! I only copped it when I had run the reservoir completely dry, I tried in vain to bleed the air lock out, I think I have the fluid pulled back into the system as far as the bleed nipples but I have no pressure on the brake pedal at all, and no matter how much and what I do I can't seem to bleed any further, there is obviously a fairly big air lock but am I to bleed anywhere else? or do something different as its a big airlock? When i try pump up pressure nothing happens when I open the bleed valve on the rear brakes, unsure if I need to do something different or bleed somewhere else??? I turned on the bike and the rear brake is doing nothing when pedals pressed the wheel is slowly spinning while on the centre stand

 

[Erdoc48]

It’s all good…you likely need a MityVac that can pull the air out of the rear brake line at the caliper bleed nipple- you can pump the brake pedal til the cows come home and won’t generate pressure- you need to vacuum bleed the rear brake. Not hard to do, but you do need the right bleeder. Even a hand vacuum pump can work - I did the same thing to my Silverwing and had to spend some time vacuum bleeding the system with a MityVac (I’m sure other makers produce the hand pump).

 

[rebelfido]

Hi Erdoc48, Thanks I have just finished fixing it, I pulled out the black diaphragm, it unfolded like a rubbery silicone collapsable lunchbox, perfectly into the reservoir when I was bleeding it the first time and watching the front brake reservoir mistakingly and because it fitted perfectly into the reservoir I just assumed it was part of it and I poured the new dot 4 fluid into it, and I obviously pulled all of liquid out of the lines and the diaphragm just stayed sucked down in the reservoir. To say I was delighted to finally figure it out, and then I properly bled the system in no time at all thanks anyway!

 

[SMSW]

Hi Erdoc48, Thanks I have just finished fixing it, I pulled out the black diaphragm, it unfolded like a rubbery silicone collapsable lunchbox, perfectly into the reservoir when I was bleeding it the first time and watching the front brake reservoir mistakingly and because it fitted perfectly into the reservoir I just assumed it was part of it and I poured the new dot 4 fluid into it, and I obviously pulled all of liquid out of the lines and the diaphragm just stayed sucked down in the reservoir. To say I was delighted to finally figure it out, and then I properly bled the system in no time at all thanks anyway!

You are not the first to have done that. We won't discuss my source of information about this screwup.