Brakes still squishy after GS-911 bleed on 2003 F650GS Dakar:

[questhe]

Brakes still squishy after GS-911 bleed on 2003 F650GS Dakar:
Going on a month now on this problem.
1. Brakes became squishy at the end of a week long ride.
   I could pump them up and get some brakeing
   The feeling at the lever was that the pressure was loosening and continual pumping was required to maintain pressure/stopping power.

2. I bled the brakes and still squishy. 

3. Purchased a syringe and performed a pressure bleed - pushing the brake fluid from the bleed screw up through to the reservoir.

4. Purchased the GS-911, performed bleeding and abs cycling/testing.

The brakes now would seem to catch and get hard, yet with prolonged braking they would leak.
After a bit of braking, they leaked more continuously.

5.   Performed multiple bleeds and flushes using push/pull from the bleed screw, ensuring the lever pump is bubble free

brakes occasionally become stiff, only to fail (become squishy) with repeated application.

hypothesis: 

The abs unit is bad (no error codes).  The unit's check valves or solenoid valves have mechanically failed.

The front  brake's sealing boot is bad.  I can't find a test for this one.  inspection only?

[WayneC]

I would look at the brake lines and master cylinder before concluding the ABS unit is faulty, are the brake lines still the original lines ?

[questhe]

The SS brake lines and pads are original.   24K miles.

I removed the caliper and inspected everything. 

Going to inspect the master cylinder tonight.

[GS Jim]

"Squishy" lever is air in the system compressing and is present all the time,  doesn't sound like that by what you report so bleeding probably won't help. Is the symptom always present or only after extended use, just a little unsure by your original post. The caliper piston seals are fine unless they are leaking on the ground. Loss of pressure over time in the system without an obvious leak indicates internal bypass, possibly at the master cylinder piston cup(s).   
You can do a visual inspection of the cups but of course that requires disassembly of the master cylinder, be careful not to damage the cups yourself though.
Did you do any work on or near the brakes before this happened?

[GS Jim]

Another question, does the lever slowly creep in to the grip (front yes?) or maintain it's position and the brake effect deteriorates?

[questhe]

I just got done with master cylinder disassembly.


The pressure cup looks fine.  I think it might be a bit hard to tell if it was failed since it is required to hold huge pressure.  So, I am ordering a new one as a 24k maintenance. 

The lever will slowly pull in, even with a little force.  When riding, I have to pump it to get braking, and then also pump it to keep braking.  It releases in about 1/4 second from full brake to no braking.

If I run the gs-911 brake cycle, it will sometimes result in a hard lever (it appears to work correctly) until I use the brakes a few times.  After that, the symptom is always present.

-current path is to buy a used ABS off fleabay and R&R. 

[Jughead]

Doubt very much the ABS is at fault.  The fact that the lever slowly creeps toward the grip indicates that the master cylinder is leaking back into the reservoir.

The entire system is sealed so if the lever is creeping as you say and there is no evident brake fluid leak onto the ground, the brake fluid is going somewhere.  This "somewhere" is past the pressure seal on the master cylinder piston and back into the reservoir.

[questhe]

Thanks - I have the master rebuild kit coming.

Have you had this happen to yourself?

[GS Jim]

I've had it happen on MX bikes and also on hydraulic cylinders many times. Usually caused by contaminants in system but also wear and tear in industrial settings, in your case probably something in the fluid nicked the edge of the seal. After disassembly totally clean master cylinder and install new kit being careful with the seal. Good luck.

[questhe]

awesome!, thanks again