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Brake Master Cylinder Bleeding Issue

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Old Jun 6, 2009 | 11:56 AM
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Default Brake Master Cylinder Bleeding Issue
I just got a new brake master cylinder and am trying to bench bleed it. The problem I'm having is that brake fluid keeps filling up one reservoir and emptying the other. I checked and its level in the vice. I see no leaks. What is going on??
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Old Jun 6, 2009 | 02:23 PM
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Anyone have any ideas?
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Old Jun 6, 2009 | 03:10 PM
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Sounds like a bad master cylinder (internal leak). The two reservoirs are seperate in the event that if one fails you still have the ability to stop the car (redundant system).
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Old Jun 6, 2009 | 03:31 PM
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Originally Posted by EastCoastHD
Sounds like a bad master cylinder (internal leak). The two reservoirs are seperate in the event that if one fails you still have the ability to stop the car (redundant system).
Thats not good. Could it have anything to do with the proportioning valve?
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Old Jun 6, 2009 | 03:38 PM
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Originally Posted by jimmers
Thats not good. Could it have anything to do with the proportioning valve?
Yes, it is the proportioning valve that will slide one way or the other shutting off the front or back which has lost pressure. You can unscrew the plastic sensor to see if the valve is not set correctly.

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Old Jun 6, 2009 | 03:40 PM
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Originally Posted by MikeC4
Yes, it is the proportioning valve that will slide one way or the other shutting off the side that has lost pressure. You can unscrew the plastic sensor to see if the valve is not set correctly.

Thanks thats better news! How do I tell if its sets correctly? I checked my FSM but it doesnt show anything about adjusting it. It just shows how to replace it.
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Old Jun 6, 2009 | 03:49 PM
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Here's a picture where the proportioning valve is close to shutting off one half of the breaking system. If this bar shifts a little more to the left, the master cylinder pressure switch, which is spring loaded, will extend into the opening. This will complete a "ground" to the circuit and this will cause the BRAKE warning to light up .




Here's a pic of the spring loaded MC pressure sensor:



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Old Jun 6, 2009 | 04:12 PM
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Originally Posted by jimmers
Thanks thats better news! How do I tell if its sets correctly? I checked my FSM but it doesnt show anything about adjusting it. It just shows how to replace it.
I have not messed with one myself, but others on this forum have. You may try to re-seat it, then bench bleed again. If problem persists, I would recommend you get a replacement from the folks you purchased it from.

http://forums.corvetteforum.com/c4-t...ing-valve.html

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Old Jun 6, 2009 | 06:47 PM
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Originally Posted by MikeC4
I have not messed with one myself, but others on this forum have. You may try to re-seat it, then bench bleed again. If problem persists, I would recommend you get a replacement from the folks you purchased it from.

http://forums.corvetteforum.com/c4-t...ing-valve.html

Thanks, ill give it a try later. I bought the master cylinder from a forum member so if all else fails ill contact him. Ill report back with my findings.
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Old Jun 7, 2009 | 11:58 AM
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I re-seated the proportioning valve and bleed the brakes. It seems to have fixed the problem. Thanks for the help!
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Old Jun 7, 2009 | 02:56 PM
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Originally Posted by jimmers
I re-seated the proportioning valve and bleed the brakes. It seems to have fixed the problem. Thanks for the help!
awesome !!!!!
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