| 2003 R1150GS ABS Repair iABS on a GS |
At about 85k miles the rear ABS began to act up. Upon hard rear braking and ABS activation the rear
power assist would go off and the ABS warnings would flash. Turning the bike off and on would
reinitializing the ABS and the rear power assist would be restored and ABS became functional again,
until it's next engagement. I have regularly successfully bleed the entire system. When the problem first
arose I bled it again and found the fluid in the rear circuit to be contaminated. The issue persisted and
the fluid in the rear quickly turned to shit again. My best guess was that the rubber rear brake line was
deteriorating internally and contaminating the fluid. I installed a SS brake line and re-bled the system.
Still had the same issue so it was time to shop for an ABS unit. Last resort for me was a new one as
they are now over $2500 from BMW. I started watching Ebay for a used one and continued riding the
bike (about 6-8 months) while deciding on my next move. I found a lot of information on removing the
integrated ABS and going back to regular no power assist non ABS, but after 12 years of confidently
riding knowing the ABS was there, I could not get comfortable with that option. I know a lot of people are
not a fan of the iABS on these bikes but I like it. I also own and have put many miles on a '81 R100RT, a
'89 KLR650 and a fleet of old Honda's with cable and linkage drum brakes, so the iABS is still state of
the art for me.
I eventually found an ABS module on Ebay for around $350. It made no claim of being functional as it
was off a parts bike/wreck but it had no damage and I thought I'd roll the dice and give it try.
The swap was pretty straight forward. Working with brake fluid is always miserable, the stuff is
corrosive to paint and skin and it tends to spread everywhere like maple syrup. While swapping the unit
I also replaced the original front brake lines with SS ones, so more bleeding and mess was inevitable.
After getting everything installed, back together and bled, one of the power assist motors would not turn
off, it ran continuously. It made all the usual noises when turned on and would vary the speed/pressure
when the brakes were applied but would not stop running. I re-bled the entire system a couple of times
in the hopes that it would solve the problem but it did not.
On to PLAN-B, the Ebay module is now a donor. I also thought about sending my old unit off for repair.
There are people experimenting with rebuilding them, I decided to give it a shot myself. I completely tore
down the donor first and quickly spotted what might have been the problem of the pump running
continuously. One of the components on the circuit board had a lot of corrosion at it's base that looked
like it could have been bridging voltage to somewhere else? I'm not an electronics expert but I knew this
didn't look right.
power assist would go off and the ABS warnings would flash. Turning the bike off and on would
reinitializing the ABS and the rear power assist would be restored and ABS became functional again,
until it's next engagement. I have regularly successfully bleed the entire system. When the problem first
arose I bled it again and found the fluid in the rear circuit to be contaminated. The issue persisted and
the fluid in the rear quickly turned to shit again. My best guess was that the rubber rear brake line was
deteriorating internally and contaminating the fluid. I installed a SS brake line and re-bled the system.
Still had the same issue so it was time to shop for an ABS unit. Last resort for me was a new one as
they are now over $2500 from BMW. I started watching Ebay for a used one and continued riding the
bike (about 6-8 months) while deciding on my next move. I found a lot of information on removing the
integrated ABS and going back to regular no power assist non ABS, but after 12 years of confidently
riding knowing the ABS was there, I could not get comfortable with that option. I know a lot of people are
not a fan of the iABS on these bikes but I like it. I also own and have put many miles on a '81 R100RT, a
'89 KLR650 and a fleet of old Honda's with cable and linkage drum brakes, so the iABS is still state of
the art for me.
I eventually found an ABS module on Ebay for around $350. It made no claim of being functional as it
was off a parts bike/wreck but it had no damage and I thought I'd roll the dice and give it try.
The swap was pretty straight forward. Working with brake fluid is always miserable, the stuff is
corrosive to paint and skin and it tends to spread everywhere like maple syrup. While swapping the unit
I also replaced the original front brake lines with SS ones, so more bleeding and mess was inevitable.
After getting everything installed, back together and bled, one of the power assist motors would not turn
off, it ran continuously. It made all the usual noises when turned on and would vary the speed/pressure
when the brakes were applied but would not stop running. I re-bled the entire system a couple of times
in the hopes that it would solve the problem but it did not.
On to PLAN-B, the Ebay module is now a donor. I also thought about sending my old unit off for repair.
There are people experimenting with rebuilding them, I decided to give it a shot myself. I completely tore
down the donor first and quickly spotted what might have been the problem of the pump running
continuously. One of the components on the circuit board had a lot of corrosion at it's base that looked
like it could have been bridging voltage to somewhere else? I'm not an electronics expert but I knew this
didn't look right.
| At the right on the above picture you can see corrosion (green) in the 8 pin connector and across the bottom of what I'm guessing is a transistor. The picture below shows the clean circuit board on the original unit for comparison. |
But I'm getting ahead of myself. The first issue was how to get this thing apart? It uses a type of
security or tamperproof screw that I was not familiar with. It looks like and is close to what is called a
tri-wing, but it is shallower. I found something close in a cheap bit set from Harbor Freight but it still
did not fit tight and I had to use a Dremel Tool to grind a straight slot in some of them to get them
out. I went to the hardware store and replaced them all with metric allen head cap screws.
security or tamperproof screw that I was not familiar with. It looks like and is close to what is called a
tri-wing, but it is shallower. I found something close in a cheap bit set from Harbor Freight but it still
did not fit tight and I had to use a Dremel Tool to grind a straight slot in some of them to get them
out. I went to the hardware store and replaced them all with metric allen head cap screws.
| This is NOT a Step by Step Rebuild! I simply took a lot of pictures and worked very carefully disassembling and reassembling the unit. I cleaned and inspected everything as it came apart.The donor unit was clean on the inside and so was the front brake circuit on the original. The rear wheel circuit on the original unit was disgusting. Grit and gum were present throughout the rear circuit. I'm still at a loss for why? It saw the same service history and use as the front circuit. Because of the wear to the impeller area of the rear pump I'm still thinking the rear hose was bad internally. I'm thinking that because of the wear to the impeller the pump was not making correct pressure and would signal a fault under load and lock out the rear. What follows are a few pictures of the unit and what I found. |
