Removing and replacing brake fluid

[Quickstep192]

I have to remove a section of brake like to do a fuel line replacement job, so it seems an oppertune time to remove and replace brake fluid.

I have a vacuum fluid evaluator. Can I connect the vacuum to the bleeders in order of distance from the master cylinder and just keep sucking out fluid until the reservoir is empty, then refill the reservoir and repeat the vacuuming sequence to get most of the air out the air out of the lines, then bleed as usual?

[pampadori]

that is exactly how I did it. Used my fluid evacuator on the left rear bleeder then the other rear, then the two fronts. Replaced my brake lines and master cylinder and filled it up with fluid and used the evacuator again to pull the fluid thru to the bleeders.

Didn't have any soft pedal issues and brakes work as good as they ever did!

[HarryD]

Seems complicated to me.

I would partially depress the brake pedal. Remove the line in question (if possible, undo only one end). Cap both open ends. Do my work. Replace the brake line and flush/bleed normally. This keeps the balance of the lines filled and I need not worry about excess air in the system.

But lots of way to skin this cat.

[fanaudical]

I'm with Harry on this one; don't introduce extra air into the system (especially the master cylinder) unless you have to...

[Quickstep192]

I get what you’re saying about not introducing air into the system, but isn’t that a necessary evil if I want to completely change the fluid?

[pampadori]

you don't introduce air if you use the fluid extractor to suck thru the bleeder screws. It will pull the fluid down from the reservoir so as long as you keep fluid in it while you do this, no air.

You guys are living in the dark ages if you don't have one of these fluid evacuators. Very handy tool to have! Its a mitty vac without needing to hand pump it a thousand times. you just hook it to your air compressor and it provides constant vacuum.
I got it to change oil in our other modern cars without having to get underneath them but its proven itself useful for brake work and draining fuel tanks and other jobs too.

[emac911]

I use the Capri vac bleeder. Uses shop air to create a vacuum. Easier than pumping the mity vac.

I use a turkey baster to suck the old fluid out of the master, fill with fresh fluid and suck until I notice new fluid coming thru the clear line at the caliper. Do all four, checking the fluid level after each caliper. Works for me in most vehicles.

[GH85Carrera]

Originally Posted by HarryD

Seems complicated to me.

I would partially depress the brake pedal. Remove the line in question (if possible, undo only one end). Cap both open ends. Do my work. Replace the brake line and flush/bleed normally. This keeps the balance of the lines filled and I need not worry about excess air in the system.

But lots of way to skin this cat.

THIS!

Just partiall depress the pedal, no more fluid running to the brake lines. Do whatever repair in needed and do it right. Then do a full flush with fresh fluid.

I change my brake fluid every single spring, without fail. My 1985 911 has the original brake master cylinder and it works great and no hit of a leak.

[fanaudical]

I have a '75 and have not had the greatest luck with brake bleeding via the vacuum method. I have had much better pedal feel using the pressurize-the-reservoir-and-then-open-the-bleed-screw method.

[Quickstep192]

I know this is a stupid question, but how much new brake fluid will I need to do a complete replacement ?

[GH85Carrera]

Originally Posted by Quickstep192

I know this is a stupid question, but how much new brake fluid will I need to do a complete replacement ?

I usually look for the color change in the fluid, and I overkill. I buy the liter can of ATE fluid, and I would rather use more than needed to be 100% sure it is all new in the car. Suck out the fluid in the reservoir, then start at the right rear, then left rear, front left, and front left. Just pump until the color of the fluid changes, or it is just more than enough.

[HarryD]

Originally Posted by GH85Carrera

I usually look for the color change in the fluid, and I overkill. I buy the liter can of ATE fluid, and I would rather use more than needed to be 100% sure it is all new in the car. Suck out the fluid in the reservoir, then start at the right rear, then left rear, front left, and front left. Just pump until the color of the fluid changes, or it is just more than enough.

This is also what I do. Back in the day when you could alternate between blue and gold ATE fluid, I found that if I flushed 170 ml of fluid through each wheel, I had a complete color change. I do this annually.