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Bleeding front brakes - no joy!


Ben There

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I changed out the OEM brake lines for stainless steel braided ones and have commenced to bleed the brakes on my '98 1100RT. Rear brake was no problem and ended up with a nice firm peddle. It's the front brakes that are giving me a fit. Using the MiteyVac hooked to my air compressor, I get lots of foam bubbles when sucking fluid from the bleeder nipple. I have gone through a pint of Dot 4 with no success and a very limp brake lever. Checked all the connections and found no leaks. I am open to suggestions. I thought this would be easy!

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I had the same experience with my R1150R. I never did figure out the cause. I just kept flushing and eventually it worked out. I never saw bubbles during the last several tries but still had spongy brakes. Then all of the sudden they were solid and I quickly tightened the bleeder. I hate when I don't know the cause of a problem but was happy with the result. I'm know that doesn't really help but maybe it'll give you hope.

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Using the MiteyVac hooked to my air compressor, I get lots of foam bubbles when sucking fluid from the bleeder nipple. I have gone through a pint of Dot 4 with no success and a very limp brake lever. Checked all the connections and found no leaks. I am open to suggestions. I thought this would be easy!

 

The run of bubbles are (probably) from the bleed nipples themselves.So try to discern between the constant run of bubbles and the pulse of bubbles that are being forced out when depressing the lever. You may find that if you just shut the bleed nipples off, and then tie the front brake lever to the fully on position and leave it over night, any air in the upper section will relieve itself into the master cylinder reservoir.

 

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You're sucking too hard with the MityVac. The big bubbles are coming from around the nipple, not from the system. I know it doesn't look like that, but they are. Set up a very gentle suction (one squeeze of the mityvac) and pump the brake lever lever slightly. You're looking fro streams of tiny bubbles. Did you bleed at the ABS pump under the tank?

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I changed out the OEM brake lines for stainless steel braided ones and have commenced to bleed the brakes on my '98 1100RT. Rear brake was no problem and ended up with a nice firm peddle. It's the front brakes that are giving me a fit. Using the MiteyVac hooked to my air compressor, I get lots of foam bubbles when sucking fluid from the bleeder nipple. I have gone through a pint of Dot 4 with no success and a very limp brake lever. Checked all the connections and found no leaks. I am open to suggestions. I thought this would be easy!

 

Morning Ben There

 

If the air bubbles are small & evenly spaced then (as mentioned by posters above) probably from the bleeder screw threads leaking air into system (this always looks bad but doesn't cause a spongy lever)

 

If you just can't get a good feeling lever then you probably still have some air trapped in the ABS modulator & will need to bleed the air from the top of that (bleed fittings on top).

 

Every now & then I used to get a 1100 ABS system that ended up with a slightly spongy front brake lever so after re-bleeding at all bleed screws I would take the bike out on a dirt road & stop hard enough get the front brakes to go into ABS a couple of times (this dislodges the air from the ABS modulator piston area). Then I would return to the shop & re-bleed all the bleeder screws. (this would usually get rid of all the air in the system).

 

I also had much better luck manually bleeding the system (ie pumping the brake lever) than trying to use vacuum bleeding as vacuum bleeding wouldn't always dislodge the trapped air. Air rises to the top in lines & ABS modulator then the vacuum bleeding would just gently move the fluid under the trapped air.

 

 

 

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Haven't bled the ABS, so I'll look into doing that and try the other suggestions also. Thanks!

 

The R1100RT brakes -ABS2 - doesn't need a Mityvac to bleed successfully. It will gravity bleed with the stock bleed valves, or if you have speed bleeders just a gentle squeeze of the front lever will move the fluid through the system. If the lever is still spongy close the bleed valve at the caliper and bleed just a little bit at the ABS. Front brakes on an ABS2 system are really easy to bleed.

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Eckhard Grohe

Just watch out for the geyser of brake fluid at the master cylinder when you release the handle. Do it slowly to minimize the fountain.

 

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Been There,

 

Try using some white PVC plumbers tape on the bleed nipple threads to eliminate those bubbles and dripping DOT4. Sometimes requires 3-4 wraps. To eliminate Eckhard's geysers, just drop a quarter (25 cent piece) in the reservoir. Works really well. Mine just stay there, front brake MC and hydraulic clutch MC.

 

I had the same issues with my ABS bleeding after installing Spieglers. It seems small bubbles get trapped in the "high spots" inside the banjo fittings and make you crazy. A rubber mallet applied lightly (tapping) to all the banjo fittings while pumping sometimes helps mine. Also, sometimes just letting it sit overnight does the trick. And as DirtRider says you'll need to bleed the ABS. On my R11S you can just prop up the rear of the gas tank to access the bleeders without having to remove it. I think the RT can be done that way, too.

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Try using some white PVC plumbers tape on the bleed nipple threads to eliminate those bubbles and dripping DOT4. Sometimes requires 3-4 wraps.

 

NO, NO, NO. NEVER EVER DO THIS. That PTFE tape 'flows' when compressed and can find itself inside the break lines and work its way to critical components. Again NEVER do this.

 

 

To eliminate Eckhard's geysers, just drop a quarter (25 cent piece) in the reservoir.

Good idea. Just make sure it is clean and remove it after you have finished bleeding the system,

 

 

 

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Morning Andy

 

 

NO, NO, NO. NEVER EVER DO THIS. That PTFE tape 'flows' when compressed and can find itself inside the break lines and work its way to critical components. Again NEVER do this.-- I guess I wouldn't say it quite this harshly but there is a lot of truth in not using PTFE tape for any hydraulics or fuel system thread sealing.

 

The company that I work for has banned all the PTFE type thread tapes in the shop areas due to possible contamination of hydraulic & fuel systems. We had a couple of vehicle fires (carburetor days) & some ABS failures due to the PTFE thread tape getting cut by the threads in a fitting then migrating down into the systems (this would be especially important on the top fittings on the BMW ABS-II modulator as the bleed fittings are directly on the top)

 

To eliminate Eckhard's geysers, just drop a quarter (25 cent piece) in the reservoir.

Good idea. Just make sure it is clean and remove it after you have finished bleeding the system,-- A standard quarter works good (especially if left in place) but personally I use a clean utility knife (carpet knife) blade as it fits the bottom of the reservoir perfectly & is MUCH easier to remove when full of fluid using a small pocket magnet or paper clip with end bent into a hook to go into one of the blade holes.

 

 

 

 

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Haven't bled the ABS, so I'll look into doing that and try the other suggestions also. Thanks!

 

Morning Ben There

 

To eliminate the small air bubbles in the bleed fluid & to make bleeding easier just use an old water bottle or other container. Then run a hose in through the top & have the bottom of the hose end up (& stay below) the level of fluid in the bottle. (once you start bleeding then the fluid flowing into the bottle will have enough fluid level to cover the end of the hose).

 

The fluid in the bottle with the hose end being under the fluid acts as a check valve to keep the bleed hose full of clean fluid.

 

You can put the container on the floor but that will still allow air to be sucked it at the bleeder fitting threads due to hose siphoning effect (works great otherwise but you will still see the small evenly spaced air bubbles)

 

If you place the container just above the bleeder fitting height (but below fluid reservoir height) that will break the air-siphon effect so there will be no more air bubbles (no air entering at bleeder fitting threads) as the hose will remain full of fluid all the way back to the bleeder screw threads.

 

Once you get the fluid flowing by pumping the lever or brake pedal you don't even have to close the bleeder screw as the hose end being below fluid level will act just like a sort-of check valve & prevent much if any backflow. (so just pump the lever or pedal until the fluid runs clean with no air bubbles coming out of the hose under the fluid in the bottle)-- Just keep an eye on the fluid level in the reservoir so it doesn't run dry).

 

This methods works especially good on dry systems (mostly void of original fluid) as it allows moving massive slugs of fluid (line diameter size slugs) so it tends to push the air down & out which is something air in the fluid doesn't like to do (air likes to move up in the fluid not down) when pumping the lever then closing the bleeder fitting between pump strokes.

 

wig9f1u.jpg

 

 

 

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Watching that stream of tiny bubbles, wondering if they will ever stop, can be annoying. A simple way to eliminate one source of the bubbles, without resorting to Teflon tape, for anyone bleeding brakes or clutches is to put a small gob of petroleum jelly or other grease where the bleeder screw mates with the caliper or slave cylinder. Spread it all around the bleeder to prevent air from entering via the bleeder screw's threads.

 

Of course you must maintain a tight seal between the tip of the bleeder and the hose attached to it to prevent air from entering at that junction, but the good thing here is that it is usually easy to know when air enters at this junction since it is generally because you moved the hose slightly allowing the air to slip by.

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Try using some white PVC plumbers tape on the bleed nipple threads to eliminate those bubbles and dripping DOT4. Sometimes requires 3-4 wraps.

 

NO, NO, NO. NEVER EVER DO THIS. That PTFE tape 'flows' when compressed and can find itself inside the break lines and work its way to critical components. Again NEVER do this.

 

 

To eliminate Eckhard's geysers, just drop a quarter (25 cent piece) in the reservoir.

Good idea. Just make sure it is clean and remove it after you have finished bleeding the system,

 

 

 

AndyS,

 

"... white PVC plumbers tape...", i.e. the cheap stuff. PVC is different. Also, when the tape is applied to the threads of the bleeder it is not "in" the hydraulic system, nor is it part of the seal at the bleeder. Mine have been there more than a year now, same with the quarters, no problems. I found it a lot less messy to just leave them in.

 

 

 

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Been There,

 

To eliminate Eckhard's geysers, just drop a quarter (25 cent piece) in the reservoir. Works really well. Mine just stay there, front brake MC and hydraulic clutch MC.

 

Well aren't you just a genius! I never would have thought of that.

 

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