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Lots of air in front brake

 
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waynedear



Joined: 16 Apr 2017
Posts: 21
Location: Liverpool

PostPosted: Sun May 07, 2017 8:47 am    Post subject: Lots of air in front brake Reply with quote

I have just replaced the front lines with stainless and rebuilt the back.
The abs for the back bled perfectly as did the caliper.
Now onto the front, bled at the abs pump until fluid ran clear BUT I AM STILL GETTING LOTS OF AIR BUBBLES, now as the new fluid is coming out of the pump there should be no air bubbles, master cylinder to hard pipe is tight.
Do you think I am getting air through the master cylinder piston and seals.
I have stripped this, when I loosened the screw for the piston it all shot out on its own, is that a sign of worn seals or normal ??
The bore is immaculate, clean and unmarked.

The bike is a K1100lt 1993 abs 2

Many thanks

Wayne
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N41EF
Flying Brick Rider


Joined: 23 Mar 2014
Posts: 406
Location: Aiken, SC

PostPosted: Sun May 07, 2017 6:51 pm    Post subject: Reply with quote

How are you bleeding it? I used a mighty vac to suck at the nipple and gently squeezed and released the lever. Make sure the lines are tight, and make sure you keep the tiny meter cylinder full. It's almost a two person job. Did you put the cover back on? I know if you pump and release the lever you'll get squirting back into he front master cylinder, that's the vent function.
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waynedear



Joined: 16 Apr 2017
Posts: 21
Location: Liverpool

PostPosted: Sun May 07, 2017 7:24 pm    Post subject: Reply with quote

N41EF wrote:
How are you bleeding it? I used a mighty vac to suck at the nipple and gently squeezed and released the lever. Make sure the lines are tight, and make sure you keep the tiny meter cylinder full. It's almost a two person job. Did you put the cover back on? I know if you pump and release the lever you'll get squirting back into he front master cylinder, that's the vent function.


Manually, I am very good at it, lines are tight and I use a cloth cover to catch the spurts, I am going to fit a set of new seals in master cylinder
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Grunter
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Joined: 30 Sep 2015
Posts: 367
Location: North East England

PostPosted: Mon May 08, 2017 6:54 pm    Post subject: Air Bubbles Reply with quote

I have always found that when bleeding and cannot get rid of all the bubbles I wind a type of tape around the threaded part of the bleed nipple, the sort used by plumbers to seal compression joints.

In UK it is called PTFE tape, very thin and usually white. It will seal threads against the ingress of air. If you can find some where you are, Remove the nipple and wind no more than 2 thicknesses around the threaded part of the nipple then screw it back into the calliper. Bleed as normal.

Once the brake is bled you can just leave the tape on the nipple and tighten it as normal .
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SugarHillCTD
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Joined: 10 Oct 2007
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Location: Now in Eastern Pennsylvania

PostPosted: Mon May 08, 2017 7:54 pm    Post subject: Reply with quote

Nice hint there Grunter. Thanks.
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waynedear



Joined: 16 Apr 2017
Posts: 21
Location: Liverpool

PostPosted: Tue May 09, 2017 3:22 am    Post subject: Re: Air Bubbles Reply with quote

Grunter wrote:
I have always found that when bleeding and cannot get rid of all the bubbles I wind a type of tape around the threaded part of the bleed nipple, the sort used by plumbers to seal compression joints.

In UK it is called PTFE tape, very thin and usually white. It will seal threads against the ingress of air. If you can find some where you are, Remove the nipple and wind no more than 2 thicknesses around the threaded part of the nipple then screw it back into the calliper. Bleed as normal.

Once the brake is bled you can just leave the tape on the nipple and tighten it as normal .


I shall remember that, thanks.
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Corkboy
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Joined: 26 Aug 2013
Posts: 81
Location: Cork, Ireland

PostPosted: Tue May 09, 2017 1:49 pm    Post subject: Reply with quote

Also, I pressurise the system by clamping the lever overnight. This compresses all the remaining air bubbles and helps them to float to the highest part of the system, hopefully the reservoir. When you unclamp the leaver, there should be one big bubble floating up.
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waynedear



Joined: 16 Apr 2017
Posts: 21
Location: Liverpool

PostPosted: Tue May 09, 2017 2:07 pm    Post subject: Reply with quote

Corkboy wrote:
Also, I pressurise the system by clamping the lever overnight. This compresses all the remaining air bubbles and helps them to float to the highest part of the system, hopefully the reservoir. When you unclamp the leaver, there should be one big bubble floating up.


First thing I did, made it worse. Shocked
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Grunter
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Joined: 30 Sep 2015
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PostPosted: Wed May 10, 2017 4:55 am    Post subject: Re: Air Bubbles Reply with quote

Grunter wrote:
I have always found that when bleeding and cannot get rid of all the bubbles I wind a type of tape around the threaded part of the bleed nipple, the sort used by plumbers to seal compression joints.

In UK it is called PTFE tape, very thin and usually white. It will seal threads against the ingress of air. If you can find some where you are, Remove the nipple and wind no more than 2 thicknesses around the threaded part of the nipple then screw it back into the calliper. Bleed as normal.

Once the brake is bled you can just leave the tape on the nipple and tighten it as normal .


I should have added, make sure the tape does not block the exit holes for the expelled fluid.
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waynedear



Joined: 16 Apr 2017
Posts: 21
Location: Liverpool

PostPosted: Thu May 11, 2017 3:23 pm    Post subject: Reply with quote

New master cylinder repair kit fitted, bled perfectly Very Happy
Went for a spin on a dirty alley, no one told me you had to reset the abs Shocked
Learnt how, be done tomorrow
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