When Replacing brake master cyl how do u bleed it?
08-10-04, 01:36 PM
#1
When Replacing brake master cyl how do u bleed it?
See title, I'm replacing my crusty rusty master cylinder for my brakes. I don't see an obvious way to do it. I've heard of the term 'bench bleed', but I'm not familiar with the procedure. I searched and couldnt find anything conclusive. I do have speed bleeders on my calipers, and stainless lines all around my t2. And I've heard the brake bias thing has to bled too, how would u do that? No abs. Thnx.
08-10-04, 01:44 PM
#2
Locust of the apocalypse
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Fill er up with fluid, then go to the passenger side rear brake and pull fluid from there with a mighty vac until you get no more bubbles (or you can use the old have a buddy step on the pedal, hold it down and open the fitting thing) then repeat for the other side, then the front passenger side and then the Front Drivers side.. Keep watch on the fluid and keep filling it with new. Don't stop right away if you get no bubbles... you have to push all the old fluid out of the entire line before the air gap created when you changed the master sylinder gets there.
Also, if you are using a mighty vac, don't mistake bubbles from air getting sucked down the bleeder fitting threads as air in the line.. you can take the fitting out and warp a bit of pipe thread tape around the very top threads and then screw it back till its almost tight and this will stop air from being sucked down the threads until you tighten it up after the bleeding is done
The proportiong valve doesn't have a bleed fitting on it as far as i've ever known, it gets bled witht he rest of the system.
Also, if you are using a mighty vac, don't mistake bubbles from air getting sucked down the bleeder fitting threads as air in the line.. you can take the fitting out and warp a bit of pipe thread tape around the very top threads and then screw it back till its almost tight and this will stop air from being sucked down the threads until you tighten it up after the bleeding is done
The proportiong valve doesn't have a bleed fitting on it as far as i've ever known, it gets bled witht he rest of the system.
Last edited by YearsOfDecay; 08-10-04 at 01:47 PM.
08-10-04, 01:50 PM
#4
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No.... you gotta bleed the whole system anyway incase air got into the lines. its good to fill the master cylinder up and pump it a few times (very slowly with the cap on lightly) to fill it up completely with fluid before you start pushing the lines.
08-10-04, 02:49 PM
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If you get the rebuilt Mazda MC ($60 at the local Mazda Dealer - Peoria) it comes with bench bleeding lines (I was shocked). Worked like a charm except the part where I removed them when I was done and dribbled fluid all over.
08-11-04, 08:16 AM
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"Bench bleeding" means bleeding just the master cylinder before installing it on the car (doing "on the bench".) You can put temporary lines coming out of the m.c. to dump the fluid right back into the reservoir, with the m.c. in a vise, and pump it using a screwdriver or whatever to fit in the back of it, until no more bubbles emerge into the reservoir. It's just a way of getting the air out of the m.c. before it goes on the car.
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