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1Back to top Go down   Rear Master Cylinder leaking Empty Rear Master Cylinder leaking on Mon Mar 16, 2015 7:14 am

elukros

elukros
active member
active member
Hello,
This morning I discovered a small spot of brake fluid on the floor, just underneath the rear master cylinder.
After some investigation, I found out that it comes from the screw that retains the cylinder piston.

Rear Master Cylinder leaking Rear_m11

The bolt was tightened with 7 Nm and for a reason or another it starts to leak.
Did I push the cylinder too deep (while applying brakes), damaging the screw thread and thus causing this leak?
Any suggestions how to solve this leak.
Are my brake pedal adjustments correct? I adjusted the screw in such way that it makes contact with the piston, without pressure on the piston. Or should I leave a gap of a few mm between piston and adjustment screw.
Need your advise.

Luk


__________________________________________________
K1100 RS ABS II 08/1993

Rear Master Cylinder leaking Be-log10
    

2Back to top Go down   Rear Master Cylinder leaking Empty Re: Rear Master Cylinder leaking on Mon Mar 16, 2015 7:27 am

Inge K.

Inge K.
VIP
VIP
It should be a aluminium gasket under the screw head.
If it's still there, it could be that it's have become flat and hard...
and you then need a new one.


__________________________________________________
Inge K.
K100RS -86. (first owner), K1100LTSE -94.
    

3Back to top Go down   Rear Master Cylinder leaking Empty Re: Rear Master Cylinder leaking on Mon Mar 16, 2015 7:35 am

elukros

elukros
active member
active member
Inge,
When I did the MC rebuild, the revision kit came with a new screw and aluminium gasket (which I installed).

Luk


__________________________________________________
K1100 RS ABS II 08/1993

Rear Master Cylinder leaking Be-log10
    

4Back to top Go down   Rear Master Cylinder leaking Empty Re: Rear Master Cylinder leaking on Mon Mar 16, 2015 7:41 am

Inge K.

Inge K.
VIP
VIP
Then a guess would be that the surfaces for the gasket haven't been clean or
not been undamaged....or the screw is cross threaded.


__________________________________________________
Inge K.
K100RS -86. (first owner), K1100LTSE -94.
    

5Back to top Go down   Rear Master Cylinder leaking Empty Re: Rear Master Cylinder leaking on Mon Mar 16, 2015 8:44 am

elukros

elukros
active member
active member
Inge,

I'll take the screw out and see. I'll have to bleed the brakes again I guess.
If there is damage to the threads, can I put some sealant (scilicones) on them?
I have a spare gasket, which I will install.

Luk


__________________________________________________
K1100 RS ABS II 08/1993

Rear Master Cylinder leaking Be-log10
    

6Back to top Go down   Rear Master Cylinder leaking Empty Re: Rear Master Cylinder leaking on Tue Mar 17, 2015 2:12 am

Inge K.

Inge K.
VIP
VIP
If the threads is damaged, I would have drilled and tapped new threads in
the next size (5 mm).


__________________________________________________
Inge K.
K100RS -86. (first owner), K1100LTSE -94.
    

7Back to top Go down   Rear Master Cylinder leaking Empty Re: Rear Master Cylinder leaking on Tue Mar 17, 2015 5:22 am

elukros

elukros
active member
active member
Inge,

Lucky me, the threads are not damaged.
MC has been repainted and as brake fluid has the capacity of eating paint. I guess that the paint dissolved, creating a small gap between gasket and retaining screw, causing the leak to become more important as the paint dissolves more.
I'll take out the MC, clean the surface between gasket and MC, install a new gasket, torque the screw with 7Nm and hopefully the leak will be cured.
If not, should I apply some sealant on the screw (something like Locktite fluid gasket)?
Don't like the idea of having to replace the whole MC just for a stupid bolt leaking.

Luk


__________________________________________________
K1100 RS ABS II 08/1993

Rear Master Cylinder leaking Be-log10
    

8Back to top Go down   Rear Master Cylinder leaking Empty Re: Rear Master Cylinder leaking on Tue Mar 17, 2015 9:41 am

Inge K.

Inge K.
VIP
VIP
I think it's gonna be a very small chance that it gonna leak when you have clean
surfaces and a new gasket.

If you afterall should be so unlucky .... Loctite would be OK, take care so you
don't get any of it inside the pump...and let it have full cure time before filling
any brake fluid.


__________________________________________________
Inge K.
K100RS -86. (first owner), K1100LTSE -94.
    

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