Does the master cylinder have to be bench bled when..

[DetroitIron]

Hi guys....several hours of searching on here has not confirmed something.... I had a rear hard brake line give out. While replacing the line I lost all the fluid in the rear portion of my master cylinder (dash brake light came on). I replaced the line and am having a difficult time bleeding the brakes. Do I need to bench bleed the master cylinder when replacing a rear brake line? Thanks,

I have an 85 K20
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[Restrorob]

No, Just let it gravity bleed for a little bit then do the pump-up bleed process.....

[DetroitIron]

Ok great thanks. I have tried that and the pedal is pretty soft ..was hoping I wouldn't have to remove lines from master as I'm sure that will destroy the lines. I read something about adjusting the rear brakes so the shoes are close to the drums to get the pedal push to draw plenty of fluid??
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[jasonw]

Don't forget that you have to reset the button on the valve that is mounted on the frame near the steering box...otherwise you will have the light on the dash and no rear brake pressure.
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[DetroitIron]

Originally Posted by jasonw

Don't forget that you have to reset the button on the valve that is mounted on the frame near the steering box...otherwise you will have the light on the dash and no rear brake pressure.
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Thanks. So if dash light is off...valve is reset? My light is off now
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[mgchevyparts]

The shuttle valve in the prop valve moved when you lost your fluid, that is what triggered the light to come on. If it's back off then it must have moved back to center. If it isn't centered you can reset it by opening a front and a rear bleeder at the same time while bleeding to equalize the pressure to move it back into position.

[jasonw]

If you get fluid coming out when you bleed the rear, you are good to go.
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[krazy_texan]

When bleeding your brakes have done one press the pedal then put your finger over the hole on the bleeder screw before they release the pedal once released remove your finger and repeat the process. What this does is prevents air from being sucked back in the line when the pedal is released. Do this and you should have it within a few pumps it never fails or hasn't for me atleast
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[wraprail]

Originally Posted by krazy_texan

When bleeding your brakes have done one press the pedal then put your finger over the hole on the bleeder screw before they release the pedal once released remove your finger and repeat the process. What this does is prevents air from being sucked back in the line when the pedal is released. Do this and you should have it within a few pumps it never fails or hasn't for me atleast
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You hear the kraziest things here. Lol
What you need is a container with a little clean brake fluid in it ( i use a 2 liter soda bottle) and some clear plastic tubing that will fit tight on the bleeder screw. Keep the end submerged in brake fluid. The finger method is just krazy.
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[frog210]

i would bench bleed the mc, you can buy a bleeder kit for a few bucks or do it with your fingers, i just went thru this whole process 2 days ago putting on a new master cylinder\

[DetroitIron]

Thanks everyone. I just finished gravity bleeding all four lines at the wheels. The rears had plenty of bubbles before running clean, solid brake fluid. Now I'm just waiting for my friend to stop over to help with a pump and bleed at all four. Pedal still feels soft the first few inches when pushing it. Hoping the pump/bleed will firm things up. Any other advice is welcome. Thanks Again

[krazy_texan]

I've tried all sorts of methods including the bottle method seems like every truck is different my 65 c10 I could not get that truck to bleed for anything ive had some bleed easy and some not
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