Bleeding brakes!

[steve'o]

Been doing a bit of maintenance on my 2003 1150GS with ABS.

Thought I would change all the brake and clutch fluids.

All went fine apart from the rear brake control circuit. Just cant seem to get all the air out.

Have kept the resivour topped up, not allowed air in, but seem to constantly get a small amount of air in the clear bleed hose.

No sign of a leak anywhere, pumping the pedal slowly seems to help but not cure. Hose is tight on the nipple and nipple is only just open.

All brake lines were replaced last year.

Running out of ideas now. Did the front control circuit the same way and no problems.

Any clue's from the collective on what else to try?

Cheers
Steve

 

[NeilDD]

Steve
Quick thought.
It might be leaking air around the bleed nipple
Try either putting a bit of PTFE tape or thick grease on the threads and retry

HTH
Neil

 

[Slipperyeel]

In addition to NielDD's suggestion. Try and close the nipple as you're pushing the lever. A sure way to make sure air isn't going the other way...

 

[Smug]

Pump up the pedal until the brake is firm and then press on the pedal and undo the nipple at the same time. When the pedal reaches the bottom of it's travel tighten up the nipple.

Do the same again as many times as necessary keeping the reservoir topped up.

 

[Slipperyeel]

Don't wait for the peddle to reach the end of its travel. Close the nipple mid-way through its travel...

This way you can be sure you shut-off the nipple while there is flow outward, but also you'll get feedback from the peddle eg. it should stiffen up...

 

[Steptoe]

Pump up the pedal until the brake is firm and then press on the pedal and undo the nipple at the same time. When the pedal reaches the bottom of it's travel tighten up the nipple.

Do the same again as many times as necessary keeping the reservoir topped up.

His bike has the servo brake system.

 

[steve'o]

Steve
Quick thought.
It might be leaking air around the bleed nipple
Try either putting a bit of PTFE tape or thick grease on the threads and retry

HTH
Neil

Had thought of this, but just tried having the nipple only just open. This might be the next thing to try.

Cheers

 

[steve'o]

In addition to NielDD's suggestion. Try and close the nipple as you're pushing the lever. A sure way to make sure air isn't going the other way...

Already tried this thanks. Was a bit fiddly to do with the ABS unit. Not sure it made a difference.

 

[steve'o]

Mainly wondering where the air is coming from. Have not let the resivour run empty, just changing the fluid. Same process for the front control circuit and no problems.

Has anyone ever experienced air being drawn/leaking into the circuit somewhere but with no fluid leaking out?

Happens on 2 of the 3 bleed nipples on the ABS unit.

Think I will have to try the PTFE tape tonight.

Cheeers

 

[Steptoe]

Don't use a clear bleeding tube ... Use a solid black tube where you can't see the bubbles

 

[Captain Black]

Already tried this thanks. Was a bit fiddly to do with the ABS unit. Not sure it made a difference.

Maybe you need a constant vacuum ?

I did mine at my mates garage after replacing all the lines with stainless, I used the pump type bleeder that attaches to a compressor . Ive not dare have a go at the two bikes I have with ABS yet, 2002 GSA1150 and 2006 F650 Dakar.

 

[Antti]

Years and years I always used to bleed in traditional way. Sometimes removed caliber and lifted it over night up or made other tricks like that.
Until finally saw the light and bought vacuum pump. 5 min and job is usually done and its tidy too. Mine is originally ment for
oil changing but i just suck all fluids with it

 

[Steptoe]

Years and years I always used to bleed in traditional way. Sometimes removed caliber and lifted it over night up or made other tricks like that.
Until finally saw the light and bought vacuum pump. 5 min and job is usually done and its tidy too. Mine is originally ment for
oil changing but i just suck all fluids with it

Servo brakes, the OP has servo brakes. You do not use vacuum pumps on a servo system. Servo systems have their own electric pumps.

 

[Captain Black]

Servo brakes, the OP has servo brakes. You do not use vacuum pumps on a servo system. Servo systems have their own electric pumps.

Does my 02 GSA and 06 650 Dakar have servos Neil ?

 

[Ian J Hartley]

The servo brakes on the 2003 R1150GS are linked brakes, but only from the front brake lever. So when you operate the front brake lever both the front brake and rear brakes are applied proportionally. So if your front control circuit is bled OK together with the front and rear brake power circuits. Then for the most part your brakes will be fine.

The rear brake pedal only operates the rear brake. Do as "Steptoe" says use a black hose so you can't see the bubbles. The air is being drawn through the bleed nipple screw threads. Just crack the nipple, pump down pedal, close nipple and release pedal. Do it for all three blead points and you will find the brakes work fine and positive from the pedal, and the servo pump will also operate. As long as you have a firm pedal after the bleed your rear brake control circuit will be OK.


Ian

 

[Slipperyeel]

Steve'o. My comments are only appropriate for the control circuit, so ignore accordingly . I forgot you had servo when I posted.

The nipples on my control unit are also fairly imprecise and a couple behave as you're describing. But because it's the control circuit, I haven't worried so much about it. For the power circuit, well as has been mentioned before, you could let gravity do the work, but since you've got a pump, why not speed it up . The power circuit had always bled perfectly

 

[steve'o]

Thanks for all the feedback, have now sorted it, by using a few techniques and some thick grease.

 

[Slipperyeel]

What did you do with the thick grease?

Sensible answers please

 

[tadhgocuilleain]

I bled the brakes on my GS for the first time a few weeks ago and it was the exact same. It drove me nuts. After putting about a litre of fluid through it, I finally figured that it was drawing air through the threads of the nipple. If I started with the bleed hose empty, I could go through three or four iterations of pumping, opening, closing with no air in the hose, but once the hose was nearly full of fluid, air bubbles started to appear. I came to the conclusion that the brake fluid running down the hose was causing a vacuum and pulling in the air at the threads. I just stopped after every three iterations and allowed the hose to empty, then continued. That worked.

What did you do with the thick grease?

Sensible answers please

I'm guessing you smear the grease around the bleed nipple to seal the threads and prevent air getting in. A thick grease won't get pulled in by the vacuum. I'll be using that trick next time.

 

[Slipperyeel]

Ptfe tape instead...?