Trouble w/ Front Brake, Need Help. - 600RR.net
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post #1 of 23 (permalink) Old 09-10-2008, 02:26 PM Thread Starter
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Trouble w/ Front Brake, Need Help.

I lowside two weeks ago at around 35 mph. I now need to pump the lever a few times before the front brake engages. I have checked over the lines and master cylinders and there no visual damages. Is it possible that when my bike was on it's side some air got into the hydraulic system? If I bleed the lines will this go away??

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post #2 of 23 (permalink) Old 09-10-2008, 02:30 PM
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when i lowsided mine the same thing happened. it was actually a bent rotor. it would push the pads back when you rolled the bike, so you had to pump the brakes a few times before they would contact the rotor again. i'd check for that.
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post #3 of 23 (permalink) Old 09-10-2008, 02:36 PM
 
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well something doesn't sound right.

Do you have to consistantly have to 'pump' the brake?

Check over the connections & fuid levels.
Then if still not working - bleed.
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post #4 of 23 (permalink) Old 09-10-2008, 11:29 PM
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how about your lever, is it banged up any? because if it is, your master cylinder get the brunt of the force too... and is probably leaking and not holding fluid back after pressurizing the lines...
post #5 of 23 (permalink) Old 09-11-2008, 12:11 PM Thread Starter
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Quote:
Originally Posted by Knightslugger View Post
how about your lever, is it banged up any? because if it is, your master cylinder get the brunt of the force too... and is probably leaking and not holding fluid back after pressurizing the lines...
I lowsided on the left and did not touch the levers. I checked the master cylinder for any indication of leaks and did not see any. I know its not my rotors because there's not even a scratch on the front or on my fork sliders. I bled the crap of all the front lines and the master cyclinder but it still looses pressure intermittenly. Should I take the master cylinder apart and check it out? Can it be rebuilt?

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post #6 of 23 (permalink) Old 09-11-2008, 12:24 PM
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I checked the master cylinder for any indication of leaks and did not see any.
so you didn't take it apart...

Quote:
Should I take the master cylinder apart and check it out? Can it be rebuilt?
i take that as a no.

master cylinders don't leak on the outside, they leak on the inside. yes, you should take it apart and inspect it. the only points that air could have been introduced into the brake system would be around seals. lines, pistons, and the MC.
post #7 of 23 (permalink) Old 09-11-2008, 12:28 PM Thread Starter
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Originally Posted by Knightslugger View Post
so you didn't take it apart...



i take that as a no.

master cylinders don't leak on the outside, they leak on the inside. yes, you should take it apart and inspect it. the only points that air could have been introduced into the brake system would be around seals. lines, pistons, and the MC.
I did noticed after I lowsided that the rubber seal in the MC resevoir was popped forward some how.

What "pistons" are you referring to Knight?? Sorry.

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post #8 of 23 (permalink) Old 09-11-2008, 12:30 PM
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I did noticed after I lowsided that the rubber seal in the MC resevoir was popped forward some how.

What "pistons" are you referring to Knight?? Sorry.
the caliper pistons... are there any other kind of pistons in a braking system that perhaps i'm not aware of?
post #9 of 23 (permalink) Old 09-11-2008, 12:32 PM
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Quote:
Originally Posted by Knightslugger View Post
the caliper pistons... are there any other kind of pistons in a braking system that perhaps i'm not aware of?
lmfao......no i think the only ones on my bike are the caliper pistons as well. in the braking system anyway.
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post #10 of 23 (permalink) Old 09-11-2008, 12:36 PM Thread Starter
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lmfao......no i think the only ones on my bike are the caliper pistons as well. in the braking system anyway.
LOL, yeah I took both calipers of and removed the pads, checked the "pistons" and didn't see any leaks.

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post #11 of 23 (permalink) Old 09-11-2008, 12:38 PM
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and you're sure your rotors are fine? hard to believe that the MC would get damaged or even air in the system in a 35mph lowside that didn't impact the MC.
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post #12 of 23 (permalink) Old 09-11-2008, 12:39 PM
 
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So at the very least, it sounds like you need to now check the M/c.
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post #13 of 23 (permalink) Old 09-11-2008, 12:40 PM
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LOL, yeah I took both calipers of and removed the pads, checked the "pistons" and didn't see any leaks.
You'd need to push them out to inspect the seal.

did the caliper take any damage?
post #14 of 23 (permalink) Old 09-11-2008, 12:42 PM
 
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the impact on the other side may have 'jarred' it & upset the position of the diaphram.
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post #15 of 23 (permalink) Old 09-11-2008, 12:48 PM
 
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this may help:

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post #16 of 23 (permalink) Old 09-11-2008, 12:50 PM Thread Starter
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Quote:
Originally Posted by Knightslugger View Post
You'd need to push them out to inspect the seal.

did the caliper take any damage?

No damage to the calipers, so...to push out the pistons and inspect the seal I need to remove the pads and pull in on the lever?? don't laugh..my first time working on brake system.

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post #17 of 23 (permalink) Old 09-11-2008, 12:56 PM
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yes, that about sums it up... with lots of fluid.

But with no physical damage done to the braking system... i find it rather hard to believe that they WOULD leak...

Have you tried bleeding the lines yet? i know your OP asked if bleeding the lines would make it go away, but since then i have not read that you have done this.
post #18 of 23 (permalink) Old 09-11-2008, 12:59 PM
 
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KS,
post 5 - I bleed the crap out of all the lines.. etc

OP,
Did you have any air in the system when you bleed them?
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post #19 of 23 (permalink) Old 09-11-2008, 01:43 PM
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Oh, thanks pete, i missed that! there was a poster not long ago, this week i think, that did not know how to properly bleed the system, and if this is the first time Degoviet has worked on a brake system, i suspect that the bleeding was done improperly.

just to verify that this is not the case, when you bleed, you you pumped up and held the brake lever, cracked the bleeder, closed the bleeder, and released the lever fro another round of pumping. yes?
post #20 of 23 (permalink) Old 09-11-2008, 02:13 PM Thread Starter
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Quote:
Originally Posted by Knightslugger View Post
Oh, thanks pete, i missed that! there was a poster not long ago, this week i think, that did not know how to properly bleed the system, and if this is the first time Degoviet has worked on a brake system, i suspect that the bleeding was done improperly.

just to verify that this is not the case, when you bleed, you you pumped up and held the brake lever, cracked the bleeder, closed the bleeder, and released the lever fro another round of pumping. yes?
I bled the lines using a bleeding device called Mighty Vac and also did it manually.

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post #21 of 23 (permalink) Old 09-11-2008, 02:16 PM
 
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Did you get any air out?

Reason I ask is if no then you need to pull apart the M/c

If yes then air is getting in somewhere.
As KS has already said there are only 'certain' points it can come in & these need to be checked.
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post #22 of 23 (permalink) Old 09-11-2008, 02:23 PM Thread Starter
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Yes, i got air out when I bled the lines. I will have to recheck everything throughly and if that still doesn't work I will have to take it to a shop. Thank you to all you guys for the help.

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post #23 of 23 (permalink) Old 04-07-2009, 07:59 PM
 
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I did the same thing, lowsided about 35mps and my front brakes would go soft, a good way to tell is to pump the brakes up and let it sit for a min come back and test them, if they are soft then its probley air in the system, if they are still good move the bike a couple of feet and see if they go soft, if they do then the rotors are warped causing the pistons to retract into their housings
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