Rear brakes

[PhilipE]

Hi oilheads, 

I dumped my 96RT1100 backing up on my steep gravel driveway. Now my back brakes have no pressure. I tried bleeding,  I went through a lot of fluid, but no luck.

Any tips?

[dirtrider]

7 minutes ago, PhilipE said:

Hi oilheads, 

I dumped my 96RT1100 backing up on my steep gravel driveway. Now my back brakes have no pressure. I tried bleeding,  I went through a lot of fluid, but no luck.

Any tips?

Evening  Philip

 

What side did it fall over on?

 

Is the fluid PUMPING through it when bleeding using the foot pedal, or is the fluid just gravity flowing out?

 

Difficult to tell much over the internet as we can't see the motorcycle, or feel the brakes, so possibly something is bent, like (brake pedal/cylinder mounting, brackets, etc) or possibly you have some trapped air up in the ABS module (did you also bleed at the ABS module bleeders?)

[Doctare]

Did you get any debris between the pads? 

[PhilipE]

33 minutes ago, Doctare said:

Did you get any debris between the pads? 

 

[PhilipE]

Thank you Doctare and dirtrider,

I have to use the foot lever to get fluid.

It fell over on the left side. There's little if any resistance in the pedal. I have No debris in the pads. I think bleeding at the ABS module is my next choice. I was hoping to avoid taking the gas tank off.

Thanks, Philip

[PhilipE]

Hey Oilheads,

Not having much luck. I bought a cheap vacuum pump. With it, I just seem to be sucking air around the threads on the bleeder valves.  I'll try some Teflon tape and grease. 

If I press the break, the wheel will lock for 1\2 second or so, then release , while keeping the brake engaged. Makes me think I'm on the wrong path.

Thanks for any help 😁 Philip

[dirtrider]

21 minutes ago, PhilipE said:

Hey Oilheads,

Not having much luck. I bought a cheap vacuum pump. With it, I just seem to be sucking air around the threads on the bleeder valves.  I'll try some Teflon Tape and grease. 

If I press the break, the wheel will lock for 1\2 second or so, then release , while keeping the brake engaged. Makes me think I'm on the wrong path.

Thanks for any help 😁 Philip

Afternoon  PhilipE

 

DO NOT use any  Teflon Tape on any brake hydraulics (especially on an ABS system).

 

It does sound like bleeding is past it usage as it should be bled out by now. Your problem is now more pointing to a leaky piston cup inside the rear master cylinder, or a stuck piston cup in the ABS hydro unit. (more likely leaking rear master cylinder piston cup than an ABS hydro unit problem.  

 

Sometimes on older BMW 1100/1150 motorcycles if you pump the rear brake pedal  past it's normal braking stroke then it will run into a curded up bore in the normally non traveled area, then the piston cup will not hold pressure for very long.  

 

You have a few options (none easy) remove the rear brake line from the master cylinder, then plug it high with a high pressure (ie threaded) plug, then see if the pedal will hold pressure).

 

Or, just remove the rear master cylinder, disassemble it, then see if the piston cup still looks good & the cylinder bore is clean &  damage free. 

 

If the (plugged off) master cylinder holds pressure then you will need to look in other places, like the ABS hydro unit, or some sort of internal restriction/blockage in a brake hose that is acting like flow restrictor under system pressure. 

 

 

[PhilipE]

Hey Dirtrider, thanks for your help. Can I use grease around the bleeder valves ?

I might try one more time before I move on to the master cylinder.

Thanks

[dirtrider]

34 minutes ago, PhilipE said:

Hey Dirtrider, thanks for your help. Can I use grease around the bleeder valves ?

I might try one more time before I move on to the master cylinder.

Thanks

Afternoon  PhilipE

 

Yes, if you are REAL CAREFUL to not get grease into the system brake fluid.

 

Why worry about some tiny air bubbles as those are normal if using a vacuum bleeding system. If the air bubbles are small & evenly spaced close together then you know where they are coming from & know they mean nothing to the internal system bleeding as they are coming from an external (fixed size)  source. 

 

Now if you were sucking the fluid through from low to high (from the lower caliper bleeder back into the master cylinder reservoir) then that will bring the air UP on the fluid. 

 

If you get large or different sized odd air bubbles at random intervals THEN worry about that air coming from inside the brake hydraulics. 

 

Personally I'm not crazy about using vacuum bleeding on the BMW 1100 ABS-II systems to REMOVE AIR  as that type of bleeding just doesn't move large slugs of fluid through the system  like pumping the brake pedal does. If the fluid moves too slowly or with a low volume flow then it doesn't always push the air out of the high spots as the fluid can flow under the higher air pockets.

 

Vacuum bleeding is usually  just fine for fluid renewal/replacement as you are not removing air, just exchanging fluids. 

[PhilipE]

 Dear Oilheads, I plugged the master cylinder with my finger. ( The hardware store is an almost hour drive, for the plug.) It felt like I could hold it without leaking past my finger. I'll remove the master cylinder and take a look inside .

 On a different note. Using the vacuum pump, even when the bleeder valves are tightened, I can still get lots of big bubbles. Coming from the valve, not sneaking in from the plastic tube . That seems pretty wrong to me. What am I missing? Thanks

 

[PhilipE]

Thank you Dirtrider,

I hadn't seen your response until after my last post.

[dirtrider]

32 minutes ago, PhilipE said:

 

 On a different note. Using the vacuum pump, even when the bleeder valves are tightened, I can still get lots of big bubbles. Coming from the valve, not sneaking in from the plastic tube . That seems pretty wrong to me. What am I missing? Thanks

Evening    Philip

 

Not that unusual, the side hole in the bleed screw is above the actual fluid sealing/seating area so air can still seep by the threads, into that hole, then out through the center of the bleed screw even with bleeder screw closed. 

 

 

 

 

 

Quote

 

[PhilipE]

Thanks Dirtrider, 

A new master cylinder and all is good.

Evidently a rebuild kit is not available .

Phil