'94 R1100RS ABS Front Brake Malfunction

[musclehealchance]

Oilhead Owners; I recently removed the front wheel of my R1100 in order to replace the rotors, thus everything was removed involving sensors, speedo/tech fitting, etc. including the rotors and sensor rings of course. Purchased replacement rotors/bobbins, etc. Now after reassembling the front brakes duo not engage on the first draw of the lever but will engage on the second pull. On the first pull there is nothing, very soft then on the second ull it pressures up and functions normally. Recently bled all 3 bleeder valves and replaced with DOT 4 Fluid and there had been no issues until the front wheel was refitted. Fluid levels up to par, no visable air in lines. No flashing ABS system failure lights. Why no action on the first pull but on the second. a very dangerous circumstance and will not ride till resolved, thx. Bill Ed.

 

[pauls1150]

First thought is that there is indeed still an air bubble in the circuit somewhere.

Second possibility (and I'm not sure about this) - with the new rotors (and pads?), you're "wiping" a different area of the bore in the master cylinder, so maybe the piston/seal is worn.

How far back towards the handlebar does the lever come on the first pull? That may be a clue, but I don't know if it would point to one case or the other.

 

[mwatrous]

Old brake lines?

Had a very similar problem which was due to a bad brake line coming off the master cylinder. The pressure would cause the hose to balloon resulting in no back pressure. This problem occurred right after I rebuilt the master cylinder.

m@

 

[pauls1150]

Ah yes! Twenty-year-old rubber lines... definitely time to R&R the set.

 

[etinch]

I had a similar problem on my 94 RS this spring when I rebuilt the front M/C and replaced the original OEM lines with Spieglers. I was sure that I had properly bled the lines but still wasn't getting good feel in the lever, in the end I found I was having problems thoroughly bleeding the new lines and ended up buying a Mityvac to fix it.

BTW - Spieglers are a good option if you decide to replace the lines. They have great service and really understand BMW's.

 

[gsaddict]

BTW - Spieglers are a good option if you decide to replace the lines. They have great service and really understand BMW's.

After installing 25+ sets I certainly agree.

 

[musclehealchance]

Re: Front Brake Malfunction

Thx for all the experience shared on this matter. I thought its strange that since I had bled the brakes(all 3 bleed reservoirs approx. 3 mo. ago) and had been riding without this problem since then, that it does not add up for it to arise after removing the front wheel and reinstalling replacing rotors(used rotors within specs)as it has? I will re-bleed and look into replacing all lines as the majority of you suggest, thx. Bill Ed.

 

[dieselyoda]

Make sure your pads are in properly, not popping out and that calipers are truly seated on their anchors.

If the last time you bled them and the system was fine and you didn't open it, air wouldn't be my first look but if when compressing the rotors, the reservoir overfilled and you weren't aware, you left the cap on, it's possible that you have a hydro-lock in the master cylinder. First pump, you are actually creating the pressure differential between the two seals and the second pump is not really displacing any fluid but allowing the fluid not to return.

If you suspect that, wrap the m/cyl with a bunch of rags and slowly unscrew the cap to keep the inevitable mess manageable and you can always do it with an audience and beer in hand say, "See, I knew that was going to happen!"

 

[BC1100S]

If you suspect that, wrap the m/cyl with a bunch of rags and slowly unscrew the cap to keep the inevitable mess manageable...

Check the reservoir sight window first. If over-full, proceed with above.

 

[36654]

Check the reservoir sight window first. If over-full, proceed with above.

Where precisely is that on my R1100RS?

 

[BC1100S]

Where precisely is that on my R1100RS?

Oh fer cryin' out loud, don't tell me this is another engineering advantage of the "S".

Look, if you're riding an RS - and your name isn't Voni Glaves - forget about the brakes, you won't get enough speed up to need them.

 

[36654]

Oh fer cryin' out loud, don't tell me this is another engineering advantage of the "S".

More like features for those that need to watch brake fluid...........

A tad too OCD for your average tasteful and discerning RS rider.

 

[BC1100S]

...your average tasteful and discerning RS rider.

Yes, but those are about as rare as good looking RS riders.

 

[PGlaves]

When I installed new Speigler lines on Voni's RS it took longer to fill and bleed the brakes to eliminate air and mushiness than it did to remove and replace the lines.

 

[Jeff488]

So Paul, you are taking a break from helping fix the bikes of IBA riders to helping fix bikes on this forum.
You should ask for a raise, dude!!

 

[36654]

Yes, but those are about as rare as good looking RS riders

I'm pretty OK with the majority of MOA members not finding me visually attractive....

 

[m_stock10506]

Where precisely is that on my R1100RS?

Does your master cylinder have a window to view brake fluid level? When the bike is level, there should be a bubble visible in the window. It should be filled above the top of the sight glass. Whoops, the previous line should read "should NOT be filled above the top of the sight glass." There should be a bubble visible.

 

[36654]

Does your master cylinder have a window to view brake fluid level? When the bike is level, there should be a bubble visible in the window. It should be filled above the top of the sight glass.

That was my point.........there isn't one on my RS.

 

[musclehealchance]

Re: Brake bleeding issues.

The problem as I stated it is that it when I am using my Eastwood Hand Vac', I keep getting "Gobs" of air and at times very little fluid although eventually I went thru' approx' 8 reservoir fills bleeding all 4 bleed nipples. Looking at the reviews for my Eastwood Bleeding System there are several bad reviews with consumers pointing the same trouble of air somehow entering the pump withdraw line. This as I was suspecting is occurring from either a poor hose to nipple seal, which seem improbable to me as I used a narrower hose I.D., heated and snugged it onto the nipple or else air was entering from around the bleed valve within the nipple threads although only opened approx. 1/2 turn. Either way between the two possible faults, neither should actually induce air into the brake lines as it would be occurring on the outward bound pump to nipple attachment. I can not tell whether the old lines are swelled or not, those say that it is a likely needed replacement though. I'm going to perform the procedure one last time the old P.I.A. way and not use the vacuum pump therefore squeezing the brake lever and running a line direct to a reservoir.

 

[PGlaves]

The problem as I stated it is that it when I am using my Eastwood Hand Vac', I keep getting "Gobs" of air and at times very little fluid although eventually I went thru' approx' 8 reservoir fills bleeding all 4 bleed nipples. Looking at the reviews for my Eastwood Bleeding System there are several bad reviews with consumers pointing the same trouble of air somehow entering the pump withdraw line. This as I was suspecting is occurring from either a poor hose to nipple seal, which seem improbable to me as I used a narrower hose I.D., heated and snugged it onto the nipple or else air was entering from around the bleed valve within the nipple threads although only opened approx. 1/2 turn. Either way between the two possible faults, neither should actually induce air into the brake lines as it would be occurring on the outward bound pump to nipple attachment. I can not tell whether the old lines are swelled or not, those say that it is a likely needed replacement though. I'm going to perform the procedure one last time the old P.I.A. way and not use the vacuum pump therefore squeezing the brake lever and running a line direct to a reservoir.

I have never had good luck with a vacuum bleeder. Air always pulled past the threads. Go get a "one man brake bleeder" ( it's a little one-way check valve) at an auto parts store and pump away gently using very short strokes so as to not destroy the master cylinder. A good trick is to tape a wood block or something to the hand grip to save yourself from yourself.