Bleeding rear ABS control circuit-can't!

[JDD]

The order of events: (R1150RT 2002)
-Leak in the lower front brake hose.
-Replaced brake hose.
-Bleed lower front brake circuit. Using a modified filling system to keep the reservoir filled when using the brake servo to pump air out.
-Worked fine. Front brakes feel fine and strong.
-Went to back brakes. Filled back reservoir circuit under tank.
-Bled back brakes at calipers. Worked fine. No air.
THEN, the rear brake pedal had no resistance when pushed down.
-Tried to bleed the rear control circuit.
-Press pedal slowly and crack 1st nipple. (as descibed here on line) Nothing comes out. Tried for a week with all three nipples. Nothing comes out.
-Back reservoir is full.
-Went to sucking out through the nipple with a syringe.
-Little spits came out. Then back to the pedal and nothing came out.
-Can’t get any fluid through the rear control circuit system.
-Went to front control circuit to see if I was doing something wrong. Got good fluid flow with no air.
-Seems like there is no fluid in the system. Even when you pump the back brake I can not get pressure to build up.
Any ideas? I am tired of driving a car.
Thanks, JDD

[R4R&R]

Doesn't the R1150RT have fully linked brakes - meaning that the rear also activated the front caliper? Have you bled that part of the circuit too?

[JDD]

Ah, yes. They are fully linked. I have been trying the back because that is the Control circuit that I am bleeding. That will be tonight. I'll crack the rear nipple when I try a sqeeze on the front. Thanks. I'll post the results.

[iowabeakster]

I do not know the difference between the RT and the R's brake systems. I'm not sure if operating the handlebar lever would push fluid in the rear control circuit.

To the main question, I can't figure why the rear control circuit has no pressure at the pedal.

It has fluid in the master cylinder. So even if there is air in the line...when you (pump, open, close, release)...you should force the air up and out the nipple on the control unit. Does the level of fluid in the master cylinder reservoir(rear control circuit) drop as you pump the pedal? It may take quite a few pumps, but you should be pushing enough air out that the level in the master cylinder reservoir should noticibly drop.

only ideas (assuming no mechanical problems):

1. You aren't opening the correct nipple (opening one for the front circuit) on the control unit
2. You don't have the (pump...open...close...release) pattern correct and are sucking air into the system through the nipple with each pump
3. One of the nipples (which you are not working on at the time) is open and keeps sucking air into the system





Good luck

[Arbee]

leak in lower front brake hose

What sort of leak? if it was a pinhole under application of brakes the ABS system
is applying pressure at all times boiling the brake fluid, increasing pressure until
it finds a way out, usually through the side of the hose.

When you changed the front hose air may have been introduced in to the ABS modulator
as well as it could also be faulty.

[JDD]

Hi, The hose was leaking at the "hose to metal end conection" next to the control box.

Still trying to bleed the rear control circuit. No luck. Went back to the front and it bleeds fine. I am going to push some fluid into the 3 nipples in the control circut to see if I can get some pressure. If this doesn't work, I think I'll have to take it in to the dealer.

I tried bleeding at the rear caliper again. With the key on, it pumps out fluid faster when I pull the front brake handle then when I push the foot brake. Guess that is because there is air in the rear circut.
Thanks,