Bleeding brakes! Am I doing this right.

[Malcolm Leick]

Okay, I thought I knew what I was doing, but now I'm not sure.

I replaced the top section of the brake line on my 650GS twin this morning. So the new top section is of course full of air. I left the brake reservoir in a position where it wouldn't drain. Then having fitted the new brake line, I started bleeding the system.

I was expecting the brake fluid still left in the lower section of line (which I hadn't removed or drained) to come out first, followed by the air from the top line. I've now put about 350ml of new fluid into the reservoir (4 refills) but I'm still getting fluid coming out of the bottom. No air so far. Am I doing something wrong, or do I just keep pumping? I also checked the nipple next to the brake reservoir but I'm getting fluid from there too.

Where has the air gone!!!!??? I know air rises, but I am presuming it will be pushed through by the fluid coming from the reservoir.

 

[Greg Masters]

Close the bleed nipple each stroke before you release the brake lever. That was it stops the old fluid being drawn back into the caliper.

Greg

 

[Malcolm Leick]

I'm doing that. Fluid is coming out okay...it just keeps coming.

 

[Greg Masters]

I'm doing that. Fluid is coming out okay...it just keeps coming.

And is the brake lever spongy?



Greg

 

[Malcolm Leick]

If I squeeze hard it will compress right back to the handlebar. It also sounds a bit squishy.

I just realised that after the upper brake line is connected, a fixed section of line disappears off into the innards of the bike behind the engine before coming back up to the connector where the lower section of line to the brake calliper begins. Presumably that's something to do with the ABS or servo. Maybe this extra couple of metres of line is where the air is sitting and it will eventually come through? I can't see anywhere else to let the air out.

Thanks for being patient Greg. This is the first time I have attempted anything like this!

 

[Greg Masters]

I'm not familiar with the 650GS twin but there's possibly another bleed nipple on the ABS unit.

Greg

 

[Malcolm Leick]

I think it's pretty much the same as the F800GS apart from the twin discs on the front. I'll try calling my local dealer.

 

[Malcolm Leick]

After reading various threads about mysterious valves in the ABS unit, which are triggered with heavy braking, I called BMW. They confirmed there are only two places to bleed the front brakes, at the calliper and next to the reservoir.

I've been out on the bike for half an hour and the front brake seems fine. Goodness knows where the air went. I'll keep an eye on it over the next few days. No leaks, which is good.

Changing the upper brake line was a bit of a mare as I had to take the front wheel out and drop the front forks out of the top yolk, so I could get to the banjo bolt. Oh and take the side panel off.

It's amazing what people will go through for an extra two swivelling inches

My Roxspeed riser to take my Fatbars!

 

[Greggers]

You could also try the old trick of using a band or bungee to hold the brake lever on all night - that sometimes lets those last persistent bubbles rise up the line to be sucked back into the reservoir when you release it...

G

 

[marcusfordus]

Quick bleed

You should have given me a shout Malcolm.

I just so happen to have a mityvac kit, even the most awkward bleeders give in to one of these. Not even the upsidedown rear caliper on a RSV millie has beaten it, cost a bit but it's earnt it's money down the workshop.