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Discussion Starter · #1 ·
I just installed a new brake booster, master cylinder, and all new brake lines. I tried to bleed the brakes and the front ones bled but the tears didn’t have fluid coming out of them. The passenger rear did have a little dribble and a couple bubbles but not much, and the driver side rear had nothing. I cracked open both the brake lines themselves where they enter the actual rear brakes and a little fluid leaks out, but I didn’t have my helper there to push the brakes when I did that.

Looking through the site I realized I was supposed to bleed the master cylinder. I probably should have read about it before just tossing parts into the car, dumb, I know. If you were me what would your next steps be? I want to avoid taking the master cylinder out of the car if at all possible.
 

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no choice...remove/bleed/re-install MC
I just installed a new brake booster, master cylinder, and all new brake lines. I tried to bleed the brakes and the front ones bled but the tears didn’t have fluid coming out of them. The passenger rear did have a little dribble and a couple bubbles but not much, and the driver side rear had nothing. I cracked open both the brake lines themselves where they enter the actual rear brakes and a little fluid leaks out, but I didn’t have my helper there to push the brakes when I did that.

Looking through the site I realized I was supposed to bleed the master cylinder. I probably should have read about it before just tossing parts into the car, dumb, I know. If you were me what would your next steps be? I want to avoid taking the master cylinder out of the car if at all possible.
If you think you really have to bleed the master, it can be done while installed in the car. Mask off with plastic all under areas to catch any spillage of brake fluid. Need a good containment jar( I used a Costco 1 liter sauerkraut jar) and snug fitting hoses to your bleeders. And a helper to operate the brake pedal and you're off to the races.
 

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....cough....well with enough fussing and mess and a helper to "carefully" pump the pedal one likely can bleed MC once installed. But IMHO doing it on the bench (vise) using either the plastic bleed lines that likely came with the MC along with instructions how to bleed it or "donor" brake lines that direct the fluid back into, and submerged, into the MC is the way.

Fresh system, new MC (after bench bleed) gravity bleed (assisted with a slight short pedal pump or two to get the fluid moving through the lines) works well. Keep an eye on MC so it doesn't drain. If pedal is still soft after gravity bleed than the helper working pedal while doing the RR. LR, RF, LF method will resolve that

restricted or no flow to rear brakes can be a bad "rear" soft line
 

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Discussion Starter · #5 ·
As a test I put a piece of tubing on each bleeder screw on the master cylinder, cracked them open, and put the tubing back in their respective resolves, then I’ve been slowly pumping the brakes and watching bubbles come out. The car is sitting level-ish on flat ground. Will this do the trick or are a bunch of bubbles still going to be trapped inside?
 

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Question to Ponder.

Back in the day bench bleeding?

Never did it and changed MCs more times than I can remember. Pulled the old one, Bolted on a new one. Reattached the brakes lines. 2 person pump and bleed. Never ever had a problem getting air out to get a firm pedal.
 
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As a test I put a piece of tubing on each bleeder screw on the master cylinder, cracked them open, and put the tubing back in their respective resolves, then I’ve been slowly pumping the brakes and watching bubbles come out. The car is sitting level-ish on flat ground. Will this do the trick or are a bunch of bubbles still going to be trapped inside?
The car is level. Is the MC level?
 

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Discussion Starter · #8 ·
The car is level. Is the MC level?
No, it's aimed upward like how it normally would be.

I pumped the brakes on and off for a while, bubbles came out here and there and seemed to eventually stop. I made sure it had fluid in the reservoir, My wife was able to sit inside and push the pedal while I attempted to bleed the rear brakes. This time they had fluid flow through and did the normal "pedal fall to the floor" routine. Unfortunately the driver rear brake cylinder is leaking. I have new components to completely replace the rear brakes but I'd rather not pull the axle shafts unless I have to. Can I replace the brake cylinder without pulling the axle shafts?
 

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1968 Camaro LS3 TH400
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It can absolutely be done on the car…. It only takes 2-3x the amount of brake fluid and time, which is why a prudent person would bench bleed.
I’m certain there are those that can dive deeper and come up drier than I ever did.
Ive been bench bleeding M/C since the late 1970s
I’ve never failed to get high and hard ….pedal that is.
 

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Can I replace the brake cylinder without pulling the axle shafts?
Yes sir.
Just the line and two bolts ( from memory, which is not as reliable as it used to be)
A leak, while it is unlikely, can cause air to be pulled into the line, causing much more attempts at bleeding.

But buy a new one. Chances are they are rust pitted and would not be honed well enough to prevent leaks.
 

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Discussion Starter · #12 ·
It can absolutely be done on the car…. It only takes 2-3x the amount of brake fluid and time, which is why a prudent person would bench bleed.
I’m certain there are those that can dive deeper and come up drier than I ever did.
Ive been bench bleeding M/C since the late 1970s
I’ve never failed to get high and hard ….pedal that is.
Others have suggested lifting the rear end of the car so that the master cylinder sits level, is that something you'd recommend doing or don't bother?

Yes sir.
Just the line and two bolts ( from memory, which is not as reliable as it used to be)
A leak, while it is unlikely, can cause air to be pulled into the line, causing much more attempts at bleeding.

But buy a new one. Chances are they are rust pitted and would not be honed well enough to prevent leaks.
I would replace both rear wheel cylinders
I have a whole new set of rear brake components for both sides, I'm planning to pull off and replace everything I can including the cylinders, brake shoes and rotors, everything that needs changing without having to pull the axle shafts because I'm trying to avoid that for the time being. That will be a future portion of the project, for now the goal is to get it running and driving and clean up the mess I have made in my cramped garage.
 

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No, it's aimed upward like how it normally would be.

I pumped the brakes on and off for a while, bubbles came out here and there and seemed to eventually stop. I made sure it had fluid in the reservoir, My wife was able to sit inside and push the pedal while I attempted to bleed the rear brakes. This time they had fluid flow through and did the normal "pedal fall to the floor" routine. Unfortunately the driver rear brake cylinder is leaking. I have new components to completely replace the rear brakes but I'd rather not pull the axle shafts unless I have to. Can I replace the brake cylinder without pulling the axle shafts?
Yes brake line off and two small bolts and it is off if they are drum brakes. But as said above check the soft line from the solid line to the tee. They will collapse and plug and you will never get rear brake action or proper bleed.
 

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Others have suggested lifting the rear end of the car so that the master cylinder sits level, is that something you'd recommend doing or don't bother?




I have a whole new set of rear brake components for both sides, I'm planning to pull off and replace everything I can including the cylinders, brake shoes and rotors, everything that needs changing without having to pull the axle shafts because I'm trying to avoid that for the time being.
raising the rear will help keep the MC from going empty longer.....although it is going to take a way longer time trying to bleed the mc doing it while still installed. Assuming you can get it bleed that way

You should also have a new soft line for the rear also. The one above the rear end, center
 

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The proportioning valve PV will shift if you do not lock it with a tool. This will affect the ability to bleed properly.

Circuit component Line Font Automotive lighting Electric blue
 
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