Easy way to bleed master cylinder!

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Silverbullet
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Easy way to bleed master cylinder!

Post by Silverbullet » Sun Aug 14, 2016 3:39 pm

Got around to putting brake fluid in the system on my wagon today, everything was installed in the car (including master cylinder) and completely empty on fluid. I thought it wasn't going to be too hard to get fluid in the master cyl, just fill up the reservoir(s) and pump away with the bleeder open, right? :rolleyes:

About 20 minutes in with nothing coming from the bleeder(s) and no fluid disappearing from the reservoir I started to think maybe it wasn't going to be that easy. Then remembering someone on here describing their troubles with theirs and having to remove the master cyl and bleed it on the bench. Every web search on the topic says you must bleed the master on the bench! Fat chance, I wasn't undoing all those fiddly brake line nuts again and risking getting fluid everywhere on the paint job. Even the FSM has no instructions on bleeding the master, everything else about bleeding the system assumes you already have old fluid in the system.

So I stumbled on a neat little trick that got the master full and pumping with no air in about 10 minutes; apply suction to the bleeder as you pump the pedal! Is alot easier with a helper on the pedal obviously, but a piece of aquarium hose is all that's needed. Slip it over the bleeder and put some vacuum to it, when the pedal is released after being depressed I saw the fluid level drop in the reservoir and some came flowing into the hose! Once there is something in there to get the cylinder pumping then you are away, just bleed as normal with no suction. I had the whole system (all 4 wheels) bled and rock solid in about 20 minutes :D And not a leak in sight :cool:

Was pretty happy in the end - after all wheels were bled and pumping solid brake fluid, the last few drips from the bottle saw both reservoirs smack bang on the max line :cool: With no vacuum assist the pedal is rock solid, hand brake works perfectly too.
Will it ever end!?
-EA81 TWIN CARB!!!!
-L series 5 speed
-Custom paint job
-2" lift
-Full custom re-wire
-L series front end
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Cliff R
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Location: Muswellbrook/NSW

Post by Cliff R » Sun Aug 14, 2016 3:55 pm

Will need to do this when I get a new brake master cylinder from somewhere.

Did you replace the brake booster too ?
If so where did you find one ?

I could look into a rebuild kit for the master cylinder but haven't looked into this yet.

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Subyroo
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Post by Subyroo » Mon Aug 15, 2016 9:10 pm

Silverbullet wrote:apply suction to the bleeder as you pump the pedal! Is alot easier with a helper on the pedal obviously, but a piece of aquarium hose is all that's needed. Slip it over the bleeder and put some vacuum to it,
Did you use your mouth for suction or some other tool like a syringe?
Peter

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Silverbullet
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Joined: Mon Aug 23, 2010 6:20 pm
Location: Adelaide

Post by Silverbullet » Mon Aug 15, 2016 9:50 pm

Cliff, I didn't replace the brake booster but I did have it tested by the place that rebuilt my front calipers, they said the booster was working flawlessly as it was. Because of the limited room around that area, I'm using the original MY brake booster.

Subryroo, yes I did use my mouth (being very careful not to get a mouthful of brake fluid!) but a large syringe could also work. I think there are also vacuum brake bleeding tools you can get that have a pump.
Will it ever end!?
-EA81 TWIN CARB!!!!
-L series 5 speed
-Custom paint job
-2" lift
-Full custom re-wire
-L series front end
Image

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