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My back brake failed whilst filtering!

 
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damian7h



Joined: 23 Sep 2012
Posts: 14
Location: London

PostPosted: Sat Nov 17, 2012 11:42 am    Post subject: My back brake failed whilst filtering! Reply with quote

Hello fellow K11 owners, I have a 95 K1100 RS.

I was happy filtering along a 2 mile stretch of bad traffic when suddenly the back brake totally went to the bottom! Not a nice feeling Shocked, luckily I was almost at the end of the traffic queue.

The front brake was ok so I continued my journey.

After a few minutes on the open road I tested the back brake and slowly it starting working again after a few tries.

FYI: I only use my back brake at very low speeds, or to aid the breaking during a well planned stop. But most of the time I only use the front brake.

This morning I visually checked the caliper and can't find nothing out of the ordinary. There are no leaks of fluid, the caliper is well attached, the pads are in reasonable condition and the foot brake lever is in good condition too.

Any suggestions?

Should I replace the lot: pads, cylinder, hoses, fluid?

I appreciate any suggestions,

Cheers,

Damian
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K1100 RS 1995
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Scott_Anderson
Site Admin


Joined: 05 Sep 2006
Posts: 3066
Location: Central Iowa, USA

PostPosted: Sat Nov 17, 2012 12:54 pm    Post subject: Reply with quote

I moved the post here to Tech so it will get more views and replies.

I'd suggest 1st check your fluid levels and/or replace the fluid and flush the system if you haven't had it done recently. Sounds as if you may be a tad bit low.
2nd thing to check would be the seals in the foot brake master cylinder. Check for a clean bore and no "grunge" packed around the seals.
Whatever you do do, don't muck with the pedal travel stops.
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1995 K1100LT 0302044
1997 R1100RT ZC62149
Garmin StreetPilot 2820
Garmin Zumo 550
Garmin Zumo XT
"One who does not ask questions is ashamed to learn" Danish proverb
1997 K1100LT 0302488(R.I.P.)
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DLBass
Mad Brick Rider


Joined: 29 Jul 2010
Posts: 93
Location: Desborough UK

PostPosted: Sat Nov 17, 2012 5:04 pm    Post subject: Reply with quote

Fluid level???

If that's OK, change the fluid. Its got too much water in it and you boiled it up while filtering
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There is only now, yesterday is gone and is unchangeable, tomorrow is uncertain. Live in the moment.
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Blackk



Joined: 12 Nov 2012
Posts: 7

PostPosted: Sat Nov 17, 2012 5:18 pm    Post subject: Reply with quote

Check disc temperature after a ride without using it.
Sounds like some temp related fadding.
B
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1992 K 1100 LT 68000km.
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Duc750



Joined: 01 Mar 2012
Posts: 11

PostPosted: Sat Nov 17, 2012 7:37 pm    Post subject: Reply with quote

Drag the back brake less. Check you're not resting the toe of your boot on it by mistake and change the fluid. It just faded through heat. That's basically caused by one of two things, bad technique or bad maintenance
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quaddawg
Big Brick Rider


Joined: 18 Jul 2012
Posts: 64
Location: Cincinnati, Ohio

PostPosted: Sun Nov 18, 2012 8:14 am    Post subject: Reply with quote

If the brake lever went to the bottom, then I highly doubt it's just brake fading. Sounds like a master cylinder that's leaking past the seal slightly.

I'd rebuild the rear master, or at least inspect it really well.
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I am: Andrew Stanford
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1993 K1100lt touring
106K miles on the clock and rising
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Duc750



Joined: 01 Mar 2012
Posts: 11

PostPosted: Sun Nov 18, 2012 8:26 am    Post subject: Reply with quote

If a seal is gone, its gone, it can't fix itself while riding
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quaddawg
Big Brick Rider


Joined: 18 Jul 2012
Posts: 64
Location: Cincinnati, Ohio

PostPosted: Sun Nov 18, 2012 3:41 pm    Post subject: Reply with quote

Nope, not true. Have been doing this for close to 35 years (bike shop ownership and mechanic work) , have seen slightly leaky umbrella seals that will bypass leak when lightly pressing brake, but will seal when agressivly pumping, or braking.

Fade usually won't allow pedal to go to limit, unless you have been boiling the fluid, and you won't do that whilst filtering at low speeds. Fade is more like push the pedal and nothing happens, at least in my experience.

If you read his description, it says it started working again after applying it several times, this does not describe fade, fade would go away if you stayed off the brake, and allowed system to cool, not by applying it several times.

I still put my money on the master cylinder.

That being said, I have been wrong before... haha... I think... hard to remember.. (kidding)
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I am: Andrew Stanford
My shop, my passion:
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Cincinnati, Ohio

1993 K1100lt touring
106K miles on the clock and rising
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Duc750



Joined: 01 Mar 2012
Posts: 11

PostPosted: Sun Nov 18, 2012 4:29 pm    Post subject: Reply with quote

We'll see. It apparently came back after a few minutes on the opoen road which says to me progressive cooling of the brake.

The problem (I find) with the K is its quite easy to catch the brake pedal with your toe and just drag it a little bit. Its particularly easy when on and off the brake in traffic.

I've had exactly the same on mine (my daily ride is 65 miles each way to work. 15 of that is filtering. BMW brake fluid also seems to be particularly vbad for fade resistence too. The best dot 4 I've ever used for fade is red line. That's what we used to use for endurance racing
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Tim (Midland Section)
Flying Brick Rider


Joined: 08 Apr 2005
Posts: 959
Location: Cotgrave, Nottingham, England.

PostPosted: Sun Nov 18, 2012 6:37 pm    Post subject: Reply with quote

It could be both M/cyl & boiling, I have had both during 60K miles of K ownership. As the fluid is in need of changing, it would be silly not to strip & clean the master cylinder. IMHO there is a ring of dried fluid or crud (tech term) making the piston slow to return & therefore during filtering not allowing the cylinder to refill or release the brakes properly. Essentially what Scott said in the second post.
Damian, pull back the rubber at the front end of the cylinder, see if it's wet with fluid. Order a repair kit. 34 31 2 311 064.
If it's done 40K or more order one anyway, unless you know when it was last changed.
Best fluid is DOT 5.1 NOT DOT 5 http://en.wikipedia.org/wiki/DOT_5 explains.
HTH
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Regards Tim,

Grey haired riders don't get that way by pure luck
1998 K1100LTSE only 70,000 miles ATM
1996 Triumph Trophy 1200 (Sold)
1972 750 Commando
1967 BSA B40
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chas
Brick Rider


Joined: 21 Jul 2008
Posts: 37
Location: Helsinki, Finland

PostPosted: Sat Nov 24, 2012 10:01 am    Post subject: Reply with quote

I have a similar problem with my '93 RS. I took the rear caliper off to check the pads, inadvertantly loosening the bolts holding the caliper halves together. I tightened those bolts again, and after undoing the correct ones(!), realised the pads were OK. Now I have no rear brake i.e. the brake pedal goes right down with no resistance, and some fluid leaked out. Seals?

The brake was working before, although the pedal felt stiff.

Is replacing the seals difficult, and what about bleeding the brakes afterwards? The bike has ABS1.

Update: just checked the fluid level - it's empty!

One more question - do I need a Torx wrench to remove the master cylinder if needed?
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Inge K.
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Joined: 30 Apr 2011
Posts: 458
Location: Norway

PostPosted: Sat Nov 24, 2012 12:04 pm    Post subject: Reply with quote

Hi Chas!
Between the calipper halves it`s a o-ring which probably have come out of position when you did loosen the wrong bolts.
But you could be lucky, and only got air into the system.................

If your brake pads have been soaked with brake fluid, I would recommend you to change them............as the brake fluid would disolve the glue between the friction material and backing plates.

Inge K.
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chas
Brick Rider


Joined: 21 Jul 2008
Posts: 37
Location: Helsinki, Finland

PostPosted: Sat Nov 24, 2012 4:05 pm    Post subject: Reply with quote

Inge K. wrote:
Hi Chas!
Between the calipper halves it`s a o-ring which probably have come out of position when you did loosen the wrong bolts.
But you could be lucky, and only got air into the system.................

If your brake pads have been soaked with brake fluid, I would recommend you to change them............as the brake fluid would disolve the glue between the friction material and backing plates.

Inge K.


Good point. But I only started to loosen the bolts, and I didn't see any fluid leaking from the caliper.

And I now have a working brake - I bled the modulator then the caliper, and I have pressure again. There must be a leak from the master cylinder though, as the reservoir was empty and the rubber boot on the master cylinder had old fluid in it.
I'll take the bike out tomorrow, and check for leaks after a ride. If it's leaking again, I'm tempted to buy a complete master cylinder, as they only cost £100, compared to £40 for an overhaul kit (from Motorworks).

Any tips on replacing the master cylinder, anyone?

P.S. My original post should have said 'some fluid leaked from the master cylinder' (when I pressed the pedal).
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Tim (Midland Section)
Flying Brick Rider


Joined: 08 Apr 2005
Posts: 959
Location: Cotgrave, Nottingham, England.

PostPosted: Sat Nov 24, 2012 6:26 pm    Post subject: Reply with quote

As I said in post #10
Damian, pull back the rubber at the front end of the cylinder, see if it's wet with fluid. Order a repair kit. 34 31 2 311 064.

That, Chas, is why your Reservoir was empty.
Luckily for me, Mr MOT man noticed mine Crying or Very sad I should have been better than that!
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Regards Tim,

Grey haired riders don't get that way by pure luck
1998 K1100LTSE only 70,000 miles ATM
1996 Triumph Trophy 1200 (Sold)
1972 750 Commando
1967 BSA B40
G6HRN
#485
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chas
Brick Rider


Joined: 21 Jul 2008
Posts: 37
Location: Helsinki, Finland

PostPosted: Mon Nov 26, 2012 5:37 am    Post subject: Reply with quote

Tim (Midland Section) wrote:
As I said in post #10
Damian, pull back the rubber at the front end of the cylinder, see if it's wet with fluid. Order a repair kit. 34 31 2 311 064.

That, Chas, is why your Reservoir was empty.


Not quite! I've just discovered that the hose to the caliper is squirting out fluid Sad So perhaps the 'slight' leak from the m/c wasn't responsible, but I've ordered a new one, plus 2 Goodrich hoses. And the reservoir to m/c hose, just in case.
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chas
Brick Rider


Joined: 21 Jul 2008
Posts: 37
Location: Helsinki, Finland

PostPosted: Tue Dec 18, 2012 10:06 am    Post subject: Leaking master cylinder/split hose update Reply with quote

Fitted a new master cylinder plus Goodrich hoses. Everything fitted, despite the master cylinder having a different connector i.e. the original was a 'straight' fit (US spec), as opposed to a right-angle connection.

All I need to do now is sort out a slight leak from the master cylinder banjo bolt Sad Perhaps the new washers are lesser quality? I'll try annealing the old ones.
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damian7h



Joined: 23 Sep 2012
Posts: 14
Location: London

PostPosted: Sat Jan 05, 2013 12:47 pm    Post subject: Reply with quote

Thanks for all your advice fellow K11 owners!

I stopped riding for a few weeks... but back on riding the K now.....

I followed Tim advise about pulling back the rubber from the cylinder and checked for fluid but I don't see any evidence of a leak.

So I am going to change the fluid as I suspect it is quite old (looks dirty/dark on the reservoir).

Never replaced the fluid so I'll be following this guide that I found on the web, different model but the concept seems to be there:

http://advwisdom.hogranch.com/Wisdom/service_abs3.pdf

Thanks again All!

Damian
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Duc750



Joined: 01 Mar 2012
Posts: 11

PostPosted: Sat Jan 05, 2013 1:11 pm    Post subject: Reply with quote

Damian, follow that guide if you want but its not for your abs system. I believe that one is for iabs or abs 3. You will have either abs 1 or 2. If you get a haynes for the bike it tells you how to do it or download the bmw workshop manual from the web
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chas
Brick Rider


Joined: 21 Jul 2008
Posts: 37
Location: Helsinki, Finland

PostPosted: Sun Jan 06, 2013 5:00 am    Post subject: Reply with quote

damian7h wrote:


http://advwisdom.hogranch.com/Wisdom/service_abs3.pdf


Damian


I just used a bleed pipe with non-return valve, and did the ABS modulator then the rear caliper, then repeated. And when the system had presuure, the hose to the caliper split! So check carefully for leaks.
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AUSBRICK
Mad Brick Rider


Joined: 18 May 2007
Posts: 113
Location: MELBOURNE AUSTRALIA

PostPosted: Fri Feb 08, 2013 2:47 am    Post subject: Reply with quote

Almost certainly overheating as Duc 750 suggests , Iv'e had this happen many times on my 1100 lt when decending on long downhills with twisties if you use the rear a little too much it overheats and the peddle will go all the way to the stop with nothing . I think the fluid boils , the peddle returns after some fast running with no braking as it cools down.It doesn't take much on these ks for this to happen as the rear disc is poorly vented .I have tried a few scoops to get more air onto it but nothing has worked yet. Has also happened when I have accidently rested my foot on the pedal slightly which sounds like what might have caused your problem. Cheers Brick
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