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Brake master cylinder bench pressure test
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Todd
Posted 2020-11-26 12:35 PM (#606065)
Subject: Brake master cylinder bench pressure test



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Surely you all know how to test a dual-circuit master cylinder. Plug both ports and fill the opening reservoires with fluid and gently push the piston back and forth to let the master draw in the brake fluid. After a few strokes you'll feel pressure build up as you meet resistance on the screwdriver. So you know the master is OK.
I have a question about this:
With the test described above, I don't yet know whether each circuit works individually.

What has to happen if only one port is closed at a time? Has there be a resist respectivly too, if i would push with a screwdriver back and forth? This would simulate the failure of one brake circuit, which would be important to test.

Or does this only work when both ports are closed? I'm not sure about this.

I tried this:
My brandnew dual master has only resistance by stroking when the reservoire for rear brakes is closed. If i unplug the rear port and plug only the port for the front brakes, there's NO resistance when stroking. ALSO there's NO fountain when stroking at the equalizer valve.
When plug both ports, there's a lot, very strong resistance. Not able to push further.

Is that normal or is the master brake cylinder defective?


Edited by Todd 2020-11-26 12:38 PM
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wizard
Posted 2020-11-26 12:50 PM (#606066 - in reply to #606065)
Subject: Re: Brake master cylinder bench pressure test



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I never bench bleed any master cylinder. I just give the fluid some time, sometimes over night before I bleed the Circuit.
Open the mc and check the parts, seems to be common that there are something wrong lately....
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Stroller
Posted 2020-11-26 1:26 PM (#606068 - in reply to #606065)
Subject: Re: Brake master cylinder bench pressure test


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Just watch for bubbles coming out of both hoses going back into the MC. When bubbles stop, or sucking air at fittings, it's bled.
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Todd
Posted 2020-11-26 1:31 PM (#606069 - in reply to #606068)
Subject: Re: Brake master cylinder bench pressure test



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Yes you're right - as for bleeding.
But you do not know, if whether each brake circuit works individually at the dual master.
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Stroller
Posted 2020-12-10 11:48 AM (#606578 - in reply to #606065)
Subject: Re: Brake master cylinder bench pressure test


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One port feeds the front binders the other feeds the rear, unless a dual diagonal system. They both share the same res.
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