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Brake bleeding questions


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8 replies to this topic

#1 BigMattyD

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Posted 16 May 2005 - 11:43 AM

This past weekend, I replaced my 10 year old, brown brake fluid and bled the fluid out of the 4 wheels.

I used a cheap hose and bottle attachment that I found at my local auto store.

The question is, does anyone know of a system that has an in-line check valve to make the process quicker and easier for one-man operation?

I know they make those valves that replace the normal bleeder screws, but then you have to buy a set for each car, and I don't use them often.

Matt

#2 Scottbaru

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Posted 16 May 2005 - 12:07 PM

I've used the mity-vac with limited success. I made a bladder out of an old mountiain-bike innertube, hole clamped one end to the brake reservoir and inflated it. That allowed me to just open the bleed screw and let the fluid flow 'till it came out clear. Last couple times I bled I enlisted a family member to pump the brake pedal. I always use clear poly-tubing on the bleed screw into a container.

#3 frag

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Posted 16 May 2005 - 12:12 PM

I've used the mity-vac with limited success. I made a bladder out of an old mountiain-bike innertube, hole clamped one end to the brake reservoir and inflated it. That allowed me to just open the bleed screw and let the fluid flow 'till it came out clear. Last couple times I bled I enlisted a family member to pump the brake pedal. I always use clear poly-tubing on the bleed screw into a container.


When I replace the brake fluid I have to replenish the master cyl reservoir with fresh fluid more than one time and well before the end of the operation. If not, air enters the system and you have to redo the process all over again.
How do you manage with the system you describe? I must be missing something.

#4 BigMattyD

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Posted 16 May 2005 - 12:17 PM

Online I found a cheap check-valve used for aquarium tubing.

Maybe I'lll try that someday,

or maybe I'll spend 40 or 50 bucks for a pressure bleeding system. I don't plan to do this again for another year or two, though..

Matt

#5 bjwirth

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Posted 16 May 2005 - 01:08 PM

The question is, does anyone know of a system that has an in-line check valve to make the process quicker and easier for one-man operation?


Hey, I was just curious how the check valve makes it a brake bleed a one man job. do you plan to put the valve on the bleed screw, then pump the brakes yourself and then when you let go of the brakes, air wont suck back into the caliper? I don't know what kind of back pressure would be generated from letting go of the brake pedal, but I got to think a cheap aquarium check valve wont hold the pressure before air gets sucked back in.

Here's a one man procedure that isn't perfect, but easy. I don't know how often one should bleed their brakes- I guess it just depends on conditions. but I just suck out the resevoir and put the cap back on and compress each caliper- each time sucking more fluid out the resevoir. with the cap on, it genereates a little pressure in the line and air will rise to the top. then I fill it back up and step on the brakes, each time watching the resevoir.

I know, I only replace SOME of the fluid. But I got the air and diffusion will take care of any moisture until next time. If you really want, I can show you the calculations where you don't really give up that much compared to bleeding the entire system.

#6 Scottbaru

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Posted 16 May 2005 - 01:40 PM

When I replace the brake fluid I have to replenish the master cyl reservoir with fresh fluid more than one time and well before the end of the operation. If not, air enters the system and you have to redo the process all over again.
How do you manage with the system you describe? I must be missing something.

Yeah, I have to undo the innertube a couple times to replenish.

air wont suck back into the caliper?

I have trouble with air leaking around the bleed screw threads with suction or check valve systems. I've tried greasing the screw threads, no luck.

If you really want, I can show you the calculations where you don't really give up that much compared to bleeding the entire system.

Do you take into account the volume of the caliper cavity and ABS? Really you never get all that old stuff out unless you pull and clean out the caliper body. Of course I'm used to larger brakes, 4-piston calipers are stock on my other cars. I've heard you don't want to push stuff backward in the brake system, probably the stuff at the calipers is the ugliest.

#7 frag

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Posted 16 May 2005 - 01:42 PM

I have trouble with air leaking around the bleed screw threads with suction or check valve systems. I've tried greasing the screw threads, no luck.


I think that's why some people recommend removing the nipples first and screwing them back with teflon tape on the threads.

#8 Scottbaru

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Posted 16 May 2005 - 02:34 PM

I think that's why some people recommend removing the nipples first and screwing them back with teflon tape on the threads.

Now that's a good idea, if you're really careful. On a lot of industrial machines teflon tape on hydraulic/pneumatic fittings voids the warranty (including the machines I design and build). That tape can wreak havoc on valves and actuators if a bit of it comes off and clogs something. I used to use Teflon tape a lot as a maintenance guy, but it became a no-no.

#9 Andyjo

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Posted 16 May 2005 - 03:20 PM

we've got a clear tube, with a one way valve on the end of it, so when you press the brakes, stuff comes out, but when you let up, it doesn't go back in =) I think you can pick em up at a hardware store?




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