Bleeding Brakes

[Watty100]

R1200GS, 2007, 87,000 miles, ABS Gen 2 non servo brakes.
I have a serious problem with air getting into the rear brake circuit only, front brakes are good and never had air getting in.
I can bleed the brakes, including the ABS bleed test with a GS911 and get the rear working as it should, strong enough to lock the wheel and get the ABS to kick in on a little test ride outside the house.
Go for a ride and in less that 5 miles I completely lose the rear brake, pedal goes fully down to the stop and no rear brake at all. I repeat that the front brakes are unaffected.
Repeat the bleeding process, I get loads of air out including a section of fluid that is best described as frothy- photos attached.
Brake comes good again, go for a ride, brake gets a load of air in and fails, and repeat..........
I've changed the brake master cylinder, banjo to the caliper, the joint pipe that sits above the swingarm and its banjo as they often seemed a little damp, new copper washers all round, but no change.
I've had the tank off to inspect the ABS unit, all unions are tight and leak-free. I've also reverse-bled the system forcing fluid in through the caliper with a syringe.
So I went for a ride with the ABS switched off with the handlebar switch. After a 20 minute ride, the rear brake was still working.
The issue therefore appears to be with the ABS unit. At no point have I lost fluid from the brake reservoir, the level has always remained constant. No fault codes showing up with the GS911.
My questions are:
How can air enter the brake circuit via the ABS?
Is this a known problem with the ABS unit? (I know about the sticky motor brush problem, that was fixed 7 years/15000 miles ago).
Can the ABS unit be overhauled, professionally or otherwise, to fix the air leak?
Am I barking up the wrong tree and the problem lies elsewhere?

Any help or advice gratefully received.

 

[botus]

at that mileage I'd not be surprised if the rear master cyl needs a new seal - in fact the front properly would need it if its available

 

[DrFarkoff]

How can air enter the brake circuit via the ABS?
Is this a known problem with the ABS unit? (I know about the sticky motor brush problem, that was fixed 7 years/15000 miles ago).
Can the ABS unit be overhauled, professionally or otherwise, to fix the air leak?
Am I barking up the wrong tree and the problem lies elsewhere?

Any help or advice gratefully received.

So as usual "Butthole" above just fires his usual crap into the mix

To clarify your situation (Not Butthole!)

If you ride the bike without ABS switched off it is fine?

In this time do you still use the rear brake pedal ??

The later ABS units have a complex arrangement of valves /sensors, it is possible one of those has become unseated or perforated

I will try and find the video that I watched of a guy stripping the car version of the ABS block

The main difference is simply the bike has half the channels and actuators that a car has and of course no Yaw control but hopefully it gives you an idea

I think one of the main original faults for the original and hated Servo ABS was a failing pressure sensor due to it breaking up inside

 

[Watty100]

at that mileage I'd not be surprised if the rear master cyl needs a new seal - in fact the front properly would need it if its avail

As stated, I replaced the master cylinder.
Its not a serviceable component, service kits are not made for it.

 

[Watty100]

So as usual "Butthole" above just fires his usual crap into the mix

To clarify your situation (Not Butthole!)

If you ride the bike without ABS switched off it is fine?

In this time do you still use the rear brake pedal ??

The later ABS units have a complex arrangement of valves /sensors, it is possible one of those has become unseated or perforated

I will try and find the video that I watched of a guy stripping the car version of the ABS block

The main difference is simply the bike has half the channels and actuators that a car has and of course no Yaw control but hopefully it gives you an idea

I think one of the main original faults for the original and hated Servo ABS was a failing pressure sensor due to it breaking up inside

You are no doubt correct that something inside the ABS unit has failed.
I'm not sure if it is strippable by an enthusiastic amateur like me, so tomorrow morning I shall be on the phone to one of the companies that refurbishes them.
If they do no more than replace the pump motor brushes, then I'll be shopping for a used unit, there's a couple on Ebay at the moment.
Cheers for helping Dr.

 

[davegs]

Why not just dump th AB’s?.

 

[Baza 07]

You are no doubt correct that something inside the ABS unit has failed.
I'm not sure if it is strippable by an enthusiastic amateur like me, so tomorrow morning I shall be on the phone to one of the companies that refurbishes them.
If they do no more than replace the pump motor brushes, then I'll be shopping for a used unit, there's a couple on Ebay at the moment.
Cheers for helping Dr.

Hi mate have a read of this, it’s not as long winded as it looks (honest)
Thread 'And so it’s Starts '
https://www.ukgser.com/community/threads/and-so-it’s-starts-🤞🤞.479475/

 

[er-minio]

I'm not sure if it is strippable by an enthusiastic amateur like me, so tomorrow morning I shall be on the phone to one of the companies that refurbishes them.

It's one single aluminium block + electronic below.
Not sure if the solenoids can leak, doubt it.

This is mine. 2007 GS Adventure, non servo ABS.

The only thing that comes to mind is damage to the pipes for the rear brake circuit when they get to the modulator?
But I have close to zero mechanical experience.

 

[DrFarkoff]

Why not just dump th AB’s?.

Its a later version

Sort of integral to the operation of the bike

But much more fixable than the Servo Schite!

 

[DrFarkoff]

The only thing that comes to mind is damage to the pipes for the rear brake circuit when they get to the modulator?
But I have close to zero mechanical experience.

Hence my question if he uses the back brake whilst the ABS is switched off ??

So if it gets air bubbles with ABS on and using pedal "but" not with ABS off and using pedal it would be quite Logical that something in the ABS system is drawing or creating air ??

But Maybe @Watty100 misunderstood my question

 

[botus]

You are no doubt correct that something inside the ABS unit has failed.
I'm not sure if it is strippable by an enthusiastic amateur like me, so tomorrow morning I shall be on the phone to one of the companies that refurbishes them.
If they do no more than replace the pump motor brushes, then I'll be shopping for a used unit, there's a couple on Ebay at the moment.
Cheers for helping Dr.

there is another fault - mine had it years back, but I don't know what they do to fix it - it would cause the front to lock with little to no provocation, they fixed it then the brushes went a few years later - I specifically questioned if they addressed both issues first round - they didn't respond to my point, other than have it back and give it back working - 25k miles and 10 years on still OK

sorry missed in your long original post that you had already swapped the rear master cyl - never read it that far.

Thinking about the magic air (either its whizzing about around a circuit and you get the air from a master cyl) or there was air that was not out ?

the after market tools are forever tweaking and adding more features / control to the bleed process choices - the last update I noticed it says when using the ABS pump cycle - you must operate the brake lever at least three times - it runs long enough that you can do three long strokes at the front, then get on the rear peddle three times - did that on mine and the front lever has come up much firmer - yet I'd conventionally bled and got air out of a closed system at last pad change

it used to always surprise me how a dealer brake fluid change, gave a shorter travel and a firmer feels than I could ever manage - but operating that proceed and it seems to push the fluid round in a circle helps a lot - they say loosen the lid take the silly crap out then run and operate the brakes (with lid temp back on) I just ran it

 

[Santa-2512]

You need to think where can air enter the system

Master cylinders, callipers, bleed nipples , seals.

I may be wrong, but if you have a open to air problem at the ABS block , i think the fluid would be coming out not in

The brake system is a sealed system , normally filled by pulling a vacuum, and then releasing fluid in to replace the air that was vacuumed out

I've had on a CH system an air problem, I'd bleed the rads and a week later full of air

i eventually found the cause , a hole in one of the threaded fittings, that was pulling air in as the pump operated

If you suspect the ABS unit, I'd brush brake fluid over the fittings and operate the brakes and see if the fluid moves or gets sucked in

Also check the bleed nipples on the callipers you may have one corroded and letting air in that way

 

[GrinningGSer]

1200GSA 2014 ; I had very similar a year ago ( thread on here ) Rear brake pedal kept going right down . You’d think that brake master cylinder faulty , but oh no , after repeated bleeding failures … dealer replaced the ABS Master cylinder.
Hey , I cannot explain the reasoning or mechanics .
( no cost to me , because bike still on extended warranty )

 

[Watty100]

Well all of the "refurb" options are centred around replacement of the ABS pump or its motor brushes, or fixes to the electronic side of things.
That doesn't seem to need to be done as there are no fault codes on the GS911 and the pump runs when I do the bleed test. I did replace the pump 15000 miles ago, when it had the brake failure error come up on the dash.
@DrFarkoff "So if it gets air bubbles with ABS on and using pedal "but" not with ABS off and using pedal it would be quite Logical that something in the ABS system is drawing or creating air ??"
Thats exactly what I'm thinking the fault is. @GrinningGSer sounds like that was an identical issue.
I've ordered a used ABS unit so we'll see how that fares.
As to a complete ABS bypass, that's my last resort. It's not compulsory to have it on that age of bike (it was an optional extra when I bought it) but I ride in all weathers and like the presence of ABS.
It will be off for an MOT once fixed, I will ask they would have tested it with the ABS switched off, I'm curious to know myself.

 

[botus]

did you catch this bit in post 11

the after market tools are forever tweaking and adding more features / control to the bleed process choices - the last update I noticed it says when using the ABS pump cycle - you must operate the brake lever at least three times - it runs long enough that you can do three long strokes at the front, then get on the rear peddle three times - did that on mine and the front lever has come up much firmer - yet I'd conventionally bled and got air out of a closed system at last pad change

 

[Watty100]

did you catch this bit in post 11

the after market tools are forever tweaking and adding more features / control to the bleed process choices - the last update I noticed it says when using the ABS pump cycle - you must operate the brake lever at least three times - it runs long enough that you can do three long strokes at the front, then get on the rear peddle three times - did that on mine and the front lever has come up much firmer - yet I'd conventionally bled and got air out of a closed system at last pad change

Yes. Done that, multiple times. GS911 software kept up to date.

 

[Santa-2512]

Well all of the "refurb" options are centred around replacement of the ABS pump or its motor brushes, or fixes to the electronic side of things.
That doesn't seem to need to be done as there are no fault codes on the GS911 and the pump runs when I do the bleed test. I did replace the pump 15000 miles ago, when it had the brake failure error come up on the dash.
@DrFarkoff "So if it gets air bubbles with ABS on and using pedal "but" not with ABS off and using pedal it would be quite Logical that something in the ABS system is drawing or creating air ??"
Thats exactly what I'm thinking the fault is. @GrinningGSer sounds like that was an identical issue.
I've ordered a used ABS unit so we'll see how that fares.
As to a complete ABS bypass, that's my last resort. It's not compulsory to have it on that age of bike (it was an optional extra when I bought it) but I ride in all weathers and like the presence of ABS.
It will be off for an MOT once fixed, I will ask they would have tested it with the ABS switched off, I'm curious to know myself.

R1200GS, 2007, 87,000 miles, ABS Gen 2 non servo brakes.
I have a serious problem with air getting into the rear brake circuit only, front brakes are good and never had air getting in.
I can bleed the brakes, including the ABS bleed test with a GS911 and get the rear working as it should, strong enough to lock the wheel and get the ABS to kick in on a little test ride outside the house.
Go for a ride and in less that 5 miles I completely lose the rear brake, pedal goes fully down to the stop and no rear brake at all. I repeat that the front brakes are unaffected.
Repeat the bleeding process, I get loads of air out including a section of fluid that is best described as frothy- photos attached.
Brake comes good again, go for a ride, brake gets a load of air in and fails, and repeat..........
I've changed the brake master cylinder, banjo to the caliper, the joint pipe that sits above the swingarm and its banjo as they often seemed a little damp, new copper washers all round, but no change.
I've had the tank off to inspect the ABS unit, all unions are tight and leak-free. I've also reverse-bled the system forcing fluid in through the caliper with a syringe.
So I went for a ride with the ABS switched off with the handlebar switch. After a 20 minute ride, the rear brake was still working.
The issue therefore appears to be with the ABS unit. At no point have I lost fluid from the brake reservoir, the level has always remained constant. No fault codes showing up with the GS911.
My questions are:
How can air enter the brake circuit via the ABS?
Is this a known problem with the ABS unit? (I know about the sticky motor brush problem, that was fixed 7 years/15000 miles ago).
Can the ABS unit be overhauled, professionally or otherwise, to fix the air leak?
Am I barking up the wrong tree and the problem lies elsewhere?

Any help or advice gratefully received.
View attachment 451016View attachment 451017

Cavitation,

bleeding wont solve, you need to flush the system before refilling with fresh fluid

If you use previous flushed / used fluid, the air bubbles will be microscopic, and when you pressurise the system it will just come back

Have you tried it with a fully flushed system & brand new fluid?

 

[Watty100]

Cavitation,

bleeding wont solve, you need to flush the system before refilling with fresh fluid

If you use previous flushed / used fluid, the air bubbles will be microscopic, and when you pressurise the system it will just come back

Have you tried it with a fully flushed system & brand new fluid?

In a nutshell, Yes.

 

[Watty100]

Right, so the new second-hand ABS unit has arrived and is ready to fit.
One question, will it need coding to the bikes ECU for it to work, and will my basic GS911 usb edition do this if required?

 

[GrinningGSer]

I doubt that you’ll get an answer re coding , but suggest that you fit and play . You mentioned that you have a GS911, so you should use its ability to bleed the ABS unit and that way you will be able to audibly hear the ABS unit being activated . Then of course , do a road test and a real ABS test .