1150 GS caliper piston mystery

Discussion in 'GS Boxers' started by motoplus40, Apr 5, 2012.

  1. motoplus40

    motoplus40 Adventurer

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    2001 1150 GS, 37,400 mi.
    I was following the rear brake pad replacement manual from the hall of wisdom and everything was going well. I was taking advantage of a rear tire renewal and I only wanted to disassemble and lubricate the rear caliper assembly and inspect the pads.
    I separated the carrier and caliper but when I went to push back both pistons with a block of wood they wouldn't move. I didn't have a small c-clamp, tried a larger one which really could not get a centered purchase on one of the pistons, and then figured, no problem, when I reinstall I will use the hydraulic brake system pressure to get them moving.
    But after I remounted the caliper, the pistons would not budge.
    When I pumped the pedal the (original rubber) brake line bulged just above the banjo crimp, which looked a little ominous but I was getting pressure.
    Brake worked fine before I disassembled. I didn't touch the foot brake while I did the work. The pistons are equally showing about 5/16" out of the caliper.
    Wondering what I try next: more c-clamp pressure, disassemble and rebuild caliper, and how the hell did I screw this up?
    #1
  2. TUCKERS

    TUCKERS the famous james

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    Don't know.

    But be careful with C clamps on the piston face, they are rather fragile and you could punch a hole in there easily.

    (Don't ask me how I know)
    #2
  3. JurgenB

    JurgenB daily rider

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    The c-clamp action has possibly tilted the piston and jammed it. I suggest that you install a suitable grease nipple instead of the bleed screw and press the piston out with a grease pump. After that, carefully clean all parts and pieces, replace gaskets and put the caliper back together. If the piston was jammed, it and/or the caliper bore may be damaged beyond repair.
    #3
  4. AntonLargiader

    AntonLargiader Long timer

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    You have a bad brake hose! Not uncommon. It may be blocking the fluid from returning to the reservoir, but in any case it's bad. You saw it with your own eyes.
    #4
  5. motoplus40

    motoplus40 Adventurer

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    Ok my brain has been released from inaction:
    No more attempts to encourage pistons to go back, and now accepting the fact I have to take this apart.
    It may be that the pistons were canted when I tried to push them in. but they resisted even the early attempt to push by hand so I had the idea that they were stuck before..
    Yes, I did see the bubble in the brake line just before the crimp which suggested a bad line. Maybe that has something to do with the immovable pistons... (I will also finally stop resisting that I have to change to steel braided lines this year.)
    So perhaps the mystery will be solved when I drain the master cylinder and the line to the caliper. If not, it is on to the "grease pressure treatment" to release pistons and then rebuild (I don't even want to think about if I ruined the caliper or pistons, I don't see any replacements for the pistons, that would mean $450 for a caliper, then I would HAVE to win a new bike at the national rally in July.)
    Guess I gotta get back to the garage.
    #5
  6. FatChance

    FatChance Road Captain

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    First, disconnect the brake line at the caliper and try moving the pistons, watching to catch any brake fluid that squirts out of the open hole. Personally, I would never introduce anything like grease into a brake system part no matter how well you clean it. It would be better to use compressed air if you want to try to force them out.

    Or, just go to the worst case and replace it. I recently had to replace a rear caliper on my 1150GS and got more than a half dozen offers to sell used ones in the flea market from $65 to about $120. Beemerboneyard has used ones for $115. I got a very good, complete used rear caliper for $100/shipped from someone I know in this forum. No need to buy a new one for $425!
    #6
  7. I GS 1

    I GS 1 I 90S I

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    I agree, I wouldn't go anywhere near it with grease. If you did you would end up replacing the whole system
    #7
  8. rebelpacket

    rebelpacket four-stroke earth-saw

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    Stop looking to the caliper for the problem.

    Anton's assesment is correct. A bulge in the brake line indicates its failed. Since yours is a 2001, if you haven't replaced the lines yet, its most definitely the problem.

    Replace the lines with the galfer kit. Do the front ones while your at it if they haven't been done already.

    #8
  9. def

    def Ginger th wonder dog

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    Grease won't hurt anything and is a good idea. You can merely flush out the grease after things are working normally. But first, I would try compressed air...keep your fingers away from the pistons while trying compressed anything.......

    Anton is likely correct (He usually is) you've got debris in your brake system from the OE rubber lines.
    #9
  10. TUCKERS

    TUCKERS the famous james

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    It helps to fill out your profile.

    Where are you?

    I can get stainless lines cooked to order at a local aircraft supply.
    #10
  11. motoplus40

    motoplus40 Adventurer

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    I am in NYC, specifically in Queens, 5th ManCave on the right.
    #11
  12. Beezer

    Beezer Long timer

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    happened on my Y2K as well.... the rear line ballooned up. I got a replacement made at the local commercial hydraulic shop for $30. BTW, my front lines went first... they came apart inside and and blocked the fluid from returning so the brakes would stay on. They also barfed rubber hunks into the ($2200) ABS module.
    #12
  13. motoplus40

    motoplus40 Adventurer

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    It was the brake line as Anton et al predicted. Separated the caliper from the banjo, pistons went in, pressed on foot brake the bubble started in the brake line, little more pedal pressure, something popped and brake fluid flowed, bubble deflated. I probably added to the problem by twisting the brake line a little too much when disassembling.

    So now I am into new stainless lines front and rear. But how far do I go with this renovation? Does Beezer's-barfing-front- brake-lines experience suggest I have to go looking for brake line bits throughout, i.e. rebuild the caliper anyway, and somehow clean out the ABS unit? Beezer, did you actually have to buy a new ABS unit because of the barfing?
    #13
  14. Schlug

    Schlug JockeyfullofBourbon

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    put something on and stay in that position.
    I did this last year after my brake line did what yours did. It bulges, but really it comes apart inside forming a sort of check valve. Fluid gets past the flap, but cannot return back to the master cylinder. Hence: pistons stuck.

    You have an '01. No servos. The BMW uses hard-piped brake lines to the ABS unit, so it's really very simple. You have one brake line from the front master cylinder to a hard pipe, which feeds the ABS unit. You have another line from the hard pipe coming from the ABS unit to the cross over, and then the crossover, which is a hard line, to each caliper. The two hard lines are sort of in the vicinity of the front shock. Very easy.

    In the rear, you have a hard pipe to the ABS unit from the master cylinder, so no stainless line needed. You will have a short line to the rear caliper from a hard pipe which comes off the ABS. The hard line comes from the ABS almost to the right rear passenge footpeg. Connect to there and then to the rear caliper. Also very simple.

    That's the kit you can order from Spiegler. It came in about 4 days and had everything I needed aside from brake fluid. I think the change took me about 3 hours at an extremely liesurely pace and about 7 pints.

    From master cylinder to ABS line:
    [​IMG]

    Sort of just above the front shock:
    [​IMG]


    Front crossover
    [​IMG]

    rear brake
    [​IMG]

    I made this one large, if you look carefully you can see both front connections and the rear:
    [​IMG]

    Bike:
    [​IMG]
    #14
  15. I GS 1

    I GS 1 I 90S I

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    Caution. I would be very careful following this advice the flushing fluid (not specified) and the grease could harm seals/boots etc. and I am not sure how you old now if you got it all out. IMHO You would be best sticking to air
    #15
  16. 99p38a

    99p38a Been here awhile

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    get them an inch or 2 longer than stock so you have some slack. I had my front do the check valve. super easy to swap out. I think I went 2" over and after my riser and TT Hard Part, I wish I had 1 more inch....
    #16
  17. motoplus40

    motoplus40 Adventurer

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    Thanks for the photo layout. Spieglers are on the way. I was going to get the Galfer lines, which are cheaper, but dealing direct with Spiegler was much easier and faster than Galfer, who are like 3-4 weeks behind.

    I don't think I will break down the rear caliper now, since the pistons are free. I will put in a new brake pad pin and new pads and then new brake lines all around. Hope I will be running by the end of the week.

    BTW, tnx to everyone for their experience.
    #17
  18. def

    def Ginger th wonder dog

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    Grease will not harm anything and removing it would require nothing more than a squirt from a can of carb cleaner or other solvent. But, the stuck piston is now free......so this is mute.
    #18
  19. motoplus40

    motoplus40 Adventurer

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    This thread is old now but I want to try to add my bit in this area so the next person searching for info will have as much help as I continually get from this forum.
    The mystery, of course, was no mystery at all as forum members quickly advised me.
    I had a bulge in the rear brake line right before the banjo at the caliper. It was indeed the total disintegration of the rubber interior of the line with one piece acting as a "flapper valve" on my brake line and not allowing brake fluid to return to the resevoir thus holding the piston in an out position. (Easy to figure this out, just disconnect the line to the caliper and if the piston goes in, you know what that bulge was doing.)
    Warning: this is a 2001 GS I bought two years ago and have been tweaking with all the upgrades that had not been done over the years (four previous owners all service in shops). "Replace brake lines with SS" was on my list, down on my list. MISTAKE. And I had a warning, last summer the main line from the front resevoir to the T pulled apart (again at the banjo) on the road and I had to lay over on a trip an extra two days and have a shop put in a new rubber line, which cost this DIYer big bucks and MUCHO PAIN (thinking about my fully equiped garage a mere 4 hours away). (BTW, Spiegler service is all that the people on this forum says it is. They are worth the extra cash.)
    I replaced original brake lines from '01, lines that someone on the forum said were not meant to last more than 6,000 miles. I cut up all the old lines on my bench after installing new Spieglars. I was amazed at the deteriorization. It looked as if all the lines were blocked (or closed down) at multiple points. This was potentially a bad accident waiting to happen as I can be a somewhat spirited rider in the twisties.
    Bleeding: I have bled brakes for years using the pump the lever system. I ran into problems after iinstalling the new lines. No real problem on the back brake once I read here that you better start at the ABS bleeder first with so much air in the system from the line change. Also I changed the rear brake pads (and disassembled and cleaned the caliper assembly -- without removing the pistons -- and replaced with scintered pads from beemerboneyard. I was concerned because the pads had total surface drag on the rotor, that is the wheel would not freewheel at all but it could be moved easily by hand. I was worried that my new pad pin and lubrication had somehow been messed up. But a test ride with no rear brake use showed a stone cold rear rotor suggesting the pads would wear a little and move away from the rotor with time. Brake action was 100%.
    Front brake gave me a great deal of trouble. I even went out and bought a mityvac because I was getting a bubbleless bleed but still had spongy front brakes. Last year I had installed speedbleeders, which have worked nicely for me but I can see why criticisms of thread leaks detailed on this forum might well cause problems by introducing a new variable in a simple system (a la VonBaden crit). But I did find that speedbleeders and a vac system like mitivac are not a good combination.
    Finding the cause of the bleeding problem eventually cost me about three bottles of brake fluid. But that is the reason why they make adjustable shop chairs. Grab a beer (acutally its coffee more often these days), pull the pneumatic release and let the chair go down to ground level, and stare at the problem with anger subsiding and resignation setting in. The bike has hand guards. I noticed in an old service invoice from previous owner that an always-on brake light had been fixed by adjusting the handguard so it would stop interfering with the final nano-mm of lever travel. Indeed, the lever was again being stopped, and now the master cyclinder was not getting a full return. The hand guards, attached at the bar and the bar end do not fit properly and they must be aftermarket and not stock BMW. The bar attachment hole interferes with the brake cable at the master cylinder. After torturing it into adjustment, the brakes pumped up to full grab. A 20 min brake bleed had taken 2 days, but there was a bit of satisfaction too.
    So after six weeks of work, and the second winter of upgrades, my 2001 was really getting sweet (I did a rocker arm slop adjustment that removed all valve train noise - truely amazing difference, (last year I did the timing chair adjuster another huge improvement), and added a silencer on the two-brothers exhaust (-18lbs over stock).
    Then of course, two days ago, an old friend of mine, an electrician, drove by the parked bike, pulled into park, and in two seconds forgot the GS was there under its cover, and backed into it. Drove it a foot back on the center stand and threw it over into my front fence: aero windscreen and cover totaled and potentially more...
    But the problems from this area a reason for a new thread!
    #19
  20. Beezer

    Beezer Long timer

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    hmm... I lost track of this one, but you asked about my ABS. Shortly after my problem with the rotten lines my ABS quit working. I flushed it a couple times and tried some of the other fixes in a very long winded thread about dead ABS II modules, but it never recovered. It might reset for a day or 2.... or a couple miles.... or not at all, so I bought another module off or an 1150 RS. The dealer can re-program some modules from different bikes but this one would not respond (I have a friend at the dealer that tried)... eventually I grafted the brain from the GS onto the hydo unit & it's been good almost 2 years now.


    tough luck about yer skooter getting knocked over.
    #20