So I have a bad master cylinder on my 70 Swinger, how do I flush out the brake lines to run Dot 5 fluid. I want to do this so I won't have any problems with my paint. I've got to repaint my fire wall now. Will I have to take the cylinders apart and wash them out? Thanks Ronnie

I would just pump the new fluid thru till it comes out all 4 corners. from what I understand on here you can mix the 2 types so I would guess any slight amount of residual old fluid left that mixes with the new wont be an issue. Sounds like you are replacing the MC so it and the lines will have 100% of the new type in it & the only possible places where some of the old could be left is in the wheel cyls where it would not be in any danger of hitting your paint.

The two fluids are NOT compatible and will not mix.
Take a small glass jar and put a small amount of the two fluids in it. Let is sit. Then shake it vigorously. lets it settle again. Any questions ????

I would suggest you disconnect the lines and hoses
blow through them with low pressure air ( ie: 5 -10 PSI).
Flush them several times with brake clean followed with low pressure air.
Rebuild and or Replace the cylinders and calipers.
Also be aware that the bleeding process needs to be done slowly as the DOT 5 is prone to aerating if pushed through to fast

I'm just going to blow it all out and wash it with something to get it all out. I"ll take the cylinders apart and wash them out so I can be sure and get it clean.