Brake line flush

I'm getting ready to do the brakes on my M36. I have no idea what's in my lines since it's been sitting for so long. I was just looking at what I could do to clear out the lines so I don't have to go through so much DOT 5. Would compressed air work then bleed the system ?

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Sounds good, blow out with compressed air, then send some alcohol through the lines, then blow out again. If the lines are clean and you have new rebuilt wheel cylinders that are clean, I have collected the bled DOT5 with a hose and coke bottle and let it settle out the bubbles and any dirt and reused it.

Thanks that's what I'll try. I'm replacing all the wheel cylinders, rebuilt the master and air pack and all the soft lines. So all that's left is cleaning the hard lines. And putting alchohol through them should do the job.

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A siphon gun comes in handy for tasks like this.

I have two brake bleeders (the regular pressurized setup everyone uses).

I drain the system, then I fill the pressure bleeder with denatured alcohol and flush it all the way through the system (i.e. open all the bleeders).

Once I'm confident everything is out, I simply turn my air pressure regulator down to 20psi~ and hook it to the bleeder adapter on the master cylinder cap and let it run for a couple hours with all the bleeders open.

Once I know the system is dry, bleed it with your new fluid.

I've been doing this for years without issue.

Do you change out all the rubber parts after the alcohol flush?

USMC 00-08 said:

Do you change out all the rubber parts after the alcohol flush?

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That would be the wisest thing to do. After all, DOT 3 and DOT 5 brake fluid will actually penetrate the rubber through any open pores. That is one reason why using DOT 5 actually helps lubricate the seals. Though I've done it this way before and had good results. Then again I've had a master cylinder go bad after a few months doing it this way too.

USMC 00-08 said:

Do you change out all the rubber parts after the alcohol flush?

Click to expand...

rustystud said:

That would be the wisest thing to do. After all, DOT 3 and DOT 5 brake fluid will actually penetrate the rubber through any open pores. That is one reason why using DOT 5 actually helps lubricate the seals. Though I've done it this way before and had good results. Then again I've had a master cylinder go bad after a few months doing it this way too.

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I did not change out all the rubber components.

This is one of those things where I had read all of the comments about an alcohol flush and switch to BFS being a bad idea. And I got in a pickle with my '68 Road Runner and did it. And it ran for years afterwards without issues. I slowly did it to more vehicles (my '68 GTX, my '66 Coronet, Dad's '68 Chevelle, Dave's Mopars, etc., etc.) until I've now gotten to the point where I do it to most anything.

Dave has cars that had been full of DOT3, we flushed with alcohol and bled with new BFS and they've been this way for 10+ years without issues.

I know everyone says to replace the rubber and the logical side of my brain agrees. But I've gotten away with it so many times without issue, I don't know what to think anymore.