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Replacing brake fluid

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Damon
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Joined: 24 Aug 2007
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PostPosted: 19:01 - 15 Feb 2008    Post subject: Replacing brake fluid Reply with quote
I have been reading the section about changing and bleeding brakes. I was just wondering if i have got it right before i start. I bought brake fluid and a brake bleeder kit today.

so...

Remove the bleed nipple cover and attach the bleeder kit
Tap off the reservoir cap
undo the nut on the bleed nipple and drain the fluid while filling up the reservoir with new fluid?

ahh, shit im lost. I keep getting told different methods to follow.

I only need to change the fluid and have a clean up of the pistons etc.
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Mr.Everready
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Joined: 28 Mar 2003
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PostPosted: 19:13 - 15 Feb 2008    Post subject: Reply with quote
That's exactly how I done it.

I used one of those "little bleeder" thingies. Pumped the brake until the reservior was half empty, filled up and repeated a few times until the fluid coming out was clear.
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Itchy
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Joined: 07 Apr 2005
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PostPosted: 19:22 - 15 Feb 2008    Post subject: Reply with quote
The thing is all your brake fluid will pee out when you pop the pistons anyway , so just lose the brake fluid that way,

But to bleed it you do pretty much what you said just keep topping it up so that it doesn;t get more than 50% empty, if the fluid coming out the caliper bleed nipple is only fluid and no bubbles you can bleed it from the top.

Ie do up the bleed nipple and slowly pump the lever with the top of the master cylinder off, it can take 15-30 minutes of pumping it to get the minute bubbles out.
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Damon
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Joined: 24 Aug 2007
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PostPosted: 21:51 - 15 Feb 2008    Post subject: Reply with quote
Itchy wrote:
The thing is all your brake fluid will pee out when you pop the pistons anyway , so just lose the brake fluid that way,

But to bleed it you do pretty much what you said just keep topping it up so that it doesn;t get more than 50% empty, if the fluid coming out the caliper bleed nipple is only fluid and no bubbles you can bleed it from the top.

Ie do up the bleed nipple and slowly pump the lever with the top of the master cylinder off, it can take 15-30 minutes of pumping it to get the minute bubbles out.


ok so once all the fluid that is coming out of the bleed nipple is the new stuff i tighten the bleed nipple and then slowly pump the lever repeatedly to get the air bubbles out. Wont all the fluid piss out the top if i pump the lever with the lid off?

or do i pump the lever and hold it in (on position) while i fill up?

Thanks all.
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Itchy
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Joined: 07 Apr 2005
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PostPosted: 22:15 - 15 Feb 2008    Post subject: Reply with quote
Dam0n wrote:


ok so once all the fluid that is coming out of the bleed nipple is the new stuff i tighten the bleed nipple and then slowly pump the lever repeatedly to get the air bubbles out. Wont all the fluid piss out the top if i pump the lever with the lid off?

or do i pump the lever and hold it in (on position) while i fill up?

Thanks all.



Pretty much it, though as said even if no bubbles come out the bleed nipple there can be air in there judged by the firmness or lack of your brake lever.

Keep the master cylinder at 50% + capacity and you'll need to bleed less air out of it during the whole process.

if your lever is still dead soft , top the fluid up and go do something for half an hour , some of the air will self bleed,


come back the lever is still soft ? , keep pumping slowly (it won't pish out the top lest you have a massive amount of air in the system which is why you bled it at the bottom to get the big bubbles out), you should get lots of small bubbles like you see in beer and a few bigger ones, eventually after lots of pumping it'll start to firm up).

But remember each time a bubble comes the level in the master cylinder will drop a bit just keep it topped up such that the hole you can see is never exposed to the air.
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Damon
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Joined: 24 Aug 2007
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PostPosted: 22:40 - 15 Feb 2008    Post subject: Reply with quote
Itchy wrote:
Dam0n wrote:


ok so once all the fluid that is coming out of the bleed nipple is the new stuff i tighten the bleed nipple and then slowly pump the lever repeatedly to get the air bubbles out. Wont all the fluid piss out the top if i pump the lever with the lid off?

or do i pump the lever and hold it in (on position) while i fill up?

Thanks all.



Pretty much it, though as said even if no bubbles come out the bleed nipple there can be air in there judged by the firmness or lack of your brake lever.

Keep the master cylinder at 50% + capacity and you'll need to bleed less air out of it during the whole process.

if your lever is still dead soft , top the fluid up and go do something for half an hour , some of the air will self bleed,


come back the lever is still soft ? , keep pumping slowly (it won't pish out the top lest you have a massive amount of air in the system which is why you bled it at the bottom to get the big bubbles out), you should get lots of small bubbles like you see in beer and a few bigger ones, eventually after lots of pumping it'll start to firm up).

But remember each time a bubble comes the level in the master cylinder will drop a bit just keep it topped up such that the hole you can see is never exposed to the air.


ok brilliant

Also,you say go away for a while to let it self bleed. Should i leave the lid of the master cylinder off and just resting on top? or should i keep the lid on?
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garyd
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Joined: 09 Apr 2006
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PostPosted: 18:27 - 17 Feb 2008    Post subject: Reply with quote
Change the fluid,bleed brake then cable tie lever back to bar overnight ..that will do it Wink
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Damon
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Joined: 24 Aug 2007
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PostPosted: 11:05 - 18 Feb 2008    Post subject: Reply with quote
garyd wrote:
Change the fluid,bleed brake then cable tie lever back to bar overnight ..that will do it Wink



with the reservior cap on or off? Karma
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Damon
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Joined: 24 Aug 2007
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PostPosted: 19:19 - 18 Feb 2008    Post subject: Reply with quote
Hetzer wrote:
If you leave the reservoir-cap off, the fluid will absorb moisture from the air, so don't do it.

To successfully bleed the system (after you have re-assembled the calipers) you first need to fill the system with fresh fluid.

Once you have fresh fluid coming out of the nipples you need to bleed the system of air. You can try to use a kit, but you will probably fail due to air being sucked back through the nipple-threads. The solution to this is to do the procedure 'manually'.

Transparent pipe from nipple into jar with fluid in it, so that the pipe's orifice is submerged. Crack nipple open a tad, pump brake lever and hold it closed, close nipple, release lever. Repeat continuously until no bubbles are appearing in the pipe.

Tap calipers, stand bike upright, shake it, dive forks, tap reservoir, try to dislodge any hidden bubbles. Repeat bleed procedure from nipple.

Finally, with nipples and reservoir closed, pump up the brake lever and clamp it fully on with tie-wraps and leave overnight. In the morning put the pipe back on the nipple, crack nipple a tad and see what you get. If bubbles, repeat bleed procedure.



Brilliant.

Thanks, you are a star. Thumbs Up
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garyd
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Joined: 09 Apr 2006
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PostPosted: 22:49 - 18 Feb 2008    Post subject: Reply with quote
what i managed to say in one line Laughing
Hetzer wrote:
If you leave the reservoir-cap off, the fluid will absorb moisture from the air, so don't do it.

To successfully bleed the system (after you have re-assembled the calipers) you first need to fill the system with fresh fluid.

Once you have fresh fluid coming out of the nipples you need to bleed the system of air. You can try to use a kit, but you will probably fail due to air being sucked back through the nipple-threads. The solution to this is to do the procedure 'manually'.

Transparent pipe from nipple into jar with fluid in it, so that the pipe's orifice is submerged. Crack nipple open a tad, pump brake lever and hold it closed, close nipple, release lever. Repeat continuously until no bubbles are appearing in the pipe.

Tap calipers, stand bike upright, shake it, dive forks, tap reservoir, try to dislodge any hidden bubbles. Repeat bleed procedure from nipple.

Finally, with nipples and reservoir closed, pump up the brake lever and clamp it fully on with tie-wraps and leave overnight. In the morning put the pipe back on the nipple, crack nipple a tad and see what you get. If bubbles, repeat bleed procedure.

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