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Masters need to be bench bled. You can’t get all the air out of them when installed.
 

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How? That makes no sense.
Sure it does.
With rear disc brakes the adjustment is automatic.
The hydraulic seals on the current wheel cylinders weep fluid and rear brakes have to be adjusted manually.
I believe the weeping cylinders is caused by the rubber being used is not firm enough and or the porosity in the aluminum castings.
We've seen it on the Defender rear drum brake cylinders, on the series IIA & III brakes, and on the aluminum clutch hydraulics from IIA onward.
So spongy brakes aside, if you are in the process of fixing the brakes while sorting the master cylinder issues, it is a good idea to get rid of the rear drum brakes.
Why?
If you fix the master cylinder issue and still have leaking rear wheel cylinders, you may or may not fix the entire braking issue which typically is multiple problems concurrently effecting the braking system of vehicles with rear drum brakes.
We see it multiple times each month.
 

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Okay. I’ve never had a failure of drum brake on a Defender. Change the shoes when they wear out. Adjust with an oil change. They are fine. Feel and brake the same as the discs. No cost difference as you suggest.
 

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For some reason the rubber on the disc brakes doesn't fail, but when you consider the wheel cylinder weep and fail, they cost more to operate as I don't suggest, but experience in rear life on a regular basis.
 

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Discussion Starter #30
So I bench bled the master and found that when I installed it I missed getting the plunger aligned into the master cylinder correctly.
The plunger for my booster basically came out - but it seems like it’s magnetic and just sticks back in place?
Anyhow. I let it stick itself back in a fun re-bled the brakes.
Now the brakes work after ~ 2 pumps. Perhaps I need to bleed them more?
Also, do I need to consider doing something to the booster considering the plunger piece is loose?

thanks!
 

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Do you have the shoes installed correctly and adjusted on the drum brakes?
 

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Discussion Starter #32
I swapped out to disc brakes all around - they are new pads and rotors on the rear.
 

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For some reason the rubber on the disc brakes doesn't fail, but when you consider the wheel cylinder weep and fail, they cost more to operate as I don't suggest, but experience in rear life on a regular basis.
Don’t drink and post Robert. I’ve never seen a wheel cylinder fail that was not at least thirty years old. Never seen anyone bring in a new one so they can’t fail often.
 

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Don’t drink and post Robert. I’ve never seen a wheel cylinder fail that was not at least thirty years old. Never seen anyone bring in a new one so they can’t fail often.
The point I was making is that the rubber they use now-a-days is spongy and after a brief period will weep fluid, just like the aluminum clutch and slave cylinders. Having to perform the same job a second time costs money.
 
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