K1100LT Rear Brake

Hi all, about 1 month ago I purchased a 1993 K1100Lt w/45,000 miles on it. yesterday while on a ride the rear brakes locked up. I loosened the bleeder to release the pressure and rode home. today I back bled from the bleeder on the caliper to the bleeder on top of the ABS unit. I went for a ride and the rear brakes tried to lock up again. I had to loosen the bleeder to get home again. What am I missing or doing wrong. Please help...

Either the linkage has been set up so that fluid can not return to the master cyilnder via the vent port, or the vent port is closed from corrosion. Start by seeing whether the brake pedal has a little free play.

the pedal has free play, and it will pump up. I just don't understand why its trying to lock up...

kgadley01 said:

the pedal has free play, and it will pump up. I just don't understand why its trying to lock up...

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The master cylinder pumps fluid to the wheel cylinder. But if the return orifice (little hole in the master cylinder) is plugged the fluid doesn't all flow back to the master cylinder when you get off the brakes. So they drag a little. And get hot. And the trapped fluid expands. And the drag gets worse. And they get hotter. And more drag, and more heat until they lock up.

You may need to removed the master cylinder, remove the little grub screw in the side, and remove the piston. At this point you can judge the corrosion, clean things up, and blow any debris out of the hole with compressed air.

The other possibility not yet mentioned is that new pads were installed and the reservoir is so full that the fluid has no place to go. Check that first.

Thanks Paul...

If the bike has older rubber hoses on it-I have seen the internals of the rubber in hoses get so weak/bad that the rubber has collapsed. The collapse expands with the pressure-push of the pedal-but as there is no real pressure on the return trip the collapse effectively becomes a one way check valve. Sort of difficult to check-it's a time/ patience thing. HTH Gary

Omega Man said:

If the bike has older rubber hoses on it-I have seen the internals of the rubber in hoses get so weak/bad that the rubber has collapsed. The collapse expands with the pressure-push of the pedal-but as there is no real pressure on the return trip the collapse effectively becomes a one way check valve. Sort of difficult to check-it's a time/ patience thing. HTH Gary

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I had this happen on a GMC pickup. Stopped up master cylinder also.

Ralph Sims