Is it possible to bleed a master cylinder on the vehicle?

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RockinRobin

RockinRobin

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1970 Duster manual brakes. Wilwood disc in front OEM drums in back. I have bled the wheels 3 times and still get a mushy pedal. There is no evidence of leakage anywhere, including the drum brake cylinders. I'm thinking master cylinder is about all that is left. The master came in a box in the trunk when I bought it 12 years ago so it has been on the car that long. I'm also wondering if it would be cheaper/easier to just replace the master, they are pretty cheap.
 
Yes, install like normal but don't hookup the brake lines from master to car instead use the bleeder adapters in new master box and just loop line fittings back into reservoir and bench bleed on car. Once you have no more bubbles in master hook up cars lines and bleed at wheels like normal.

RockinRobin said:
1970 Duster manual brakes. Wilwood disc in front OEM drums in back. I have bled the wheels 3 times and still get a mushy pedal. There is no evidence of leakage anywhere, including the drum brake cylinders. I'm thinking master cylinder is about all that is left. The master came in a box in the trunk when I bought it 12 years ago so it has been on the car that long. I'm also wondering if it would be cheaper/easier to just replace the master, they are pretty cheap.
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Big.J.007 said:
Yes, install like normal but don't hookup the brake lines from master to car instead use the bleeder adapters in new master box and just loop line fittings back into reservoir and bench bleed on car. Once you have no more bubbles in master hook up cars lines and bleed at wheels like normal.



View attachment 1716384307
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Digging that clip/plug wire holder rig. :)
 
Big.J.007 said:
Yes, install like normal but don't hookup the brake lines from master to car instead use the bleeder adapters in new master box and just loop line fittings back into reservoir and bench bleed on car. Once you have no more bubbles in master hook up cars lines and bleed at wheels like normal.



View attachment 1716384307
Click to expand...
Yep, done it many times like that! Nice to have those clear lines to see any bubbles.
 
I find solid plugs for the master cylinder outlets. Have someone pump the pedal, while I crack the solid plugs. When it's got all the air gone the pedal Will be SOLID with the line plugs in and tight.
 
never bench bleeded in my life. install and bleed the brakes normal. route the hose from the bleeder upwards, no air can return from the bleederhose
 
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