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Discussion Starter #1
This Thanksgiving weekend, son and I are going to change out the master cylinder and replace the flex brake lines with stainless ones.

Question:
Should we bleed out the fluid first, out of the system, before taking the MC out?
Or should we disconnect the MC first, and flush out the remaining fluid once the new MC (and lines) are replaced?

What do you all recommend is best?
 

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Suck the fluid out of the master cylinder only to save you the mess when remove the lines.
 

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Here's how I do it. (You can either flush before or after but I prefer after because then any debris presently in the master won't be pushed into wheel cylinders.) 1) take some lines from a scrapped car and make up some (4) 'bench bleed' lines. These are lines that will be screwed into the line-out ports of both the old and new master cylinders and bent so that the pipes lead upwards to a level ABOVE the level in the reservoir. You need FOUR of these lines, two for each master. 2) Prepare the new master cylinder by installing the bench-bleed lines and fill with new fluid. Bench bleed the new master until it is clear of air. Set it aside. 3) Loosen/remove the mounting bolts of the old master. 4) Unscrew the lines from the old master one at a time and install the bench-bleed lines in their place. You will lose a bit of fluid but not very much and a handy rag takes care of that little bit. 5) Remove the old master from the car. 6) Install the new master with the bench-bleed lines still in place. 7) Quickly remove the bench-bleed lines and re-attach the car's lines to the new master. 8) If necessary or desired, flush the system.

HTH
Bob
 

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+1 for Bob's method. I do nearly the exact same thing.
 

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Discussion Starter #5
I understand the purpose of the bleeder lines on the new MC.

But what is the reason for adding the bleeder lines on the old MC, that you need to disconnect from the hard lines anyway?

I guess it's to minimize fluid leaking out of it, if so I was going to a) drain the reservoir from the top (per note above), and b) put a little plastic container underneath the lines as I loosened them. ...that should work just as well, right?
 

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Yes, mainly to keep things tidy. Even if you use a turkey baster to empty the reservoir there is still fluid in the cylinder itself. Also, the time it takes to put on the bench-bleed lines is far less than the time it takes to undo the second line from the master and remove the master from the booster, so there is a lot less time for fluid to make a mess and possibly drip on your paint - brake fluid is a pretty good paint remover.

Bob
 
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