General Question

Vignette's avatar

Any tips you can share on how to bench bleed a brake master cylinder?

Asked by Vignette (2874points) 4 weeks ago

I got a rough I idea from Youtube, just a little unsure on how much time it should take or how many pumps of the piston is enough. If you have done this or know of tips that make this task seamless I would appreciate it. Here is the master Cylinder if type of MC makes a difference in what to do.

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15 Answers

lucillelucillelucille's avatar

Is it actually going to be bled on the bench?

Vignette's avatar

@lucillelucillelucille That is one of my options. Youtube shows the floor as an option. I think the term “bench bleed” is simply a descriptor for the stage of the master cylinder brake repair process no as much of the horizontal surface chosen to do the bleed.

Tropical_Willie's avatar

I think I would mount master cylinder, bench bleed can be done on firewall, just don’t connect the brake line. Fill master cylinder and pump it a couple of times (refill master cylinder), now connect brake line. Bleed the furthest slave cylinder on the car FIRST, then go to next closest bleed again. . . etc.

MAKE SURE you use the same type of brake fluid as is in it now, you shouldn’t mix types of brake fluid !

I’m not a certified master mechanic. but I stayed in a Holiday Inn Express.

lucillelucillelucille's avatar

@Vignette -I’d stick it in a vice, pump the piston until no air is expelled only fluid. transfer to car,connect lines and gravity bleed if you have no one to help you bleed each corner.
Could take a few hours, maybe even a three hour tour

Vignette's avatar

Thanks @Tropical_Willie! The one YT video showed tilting the master cylinder away from the chamber being bled and once that one is cleared tip it the other way to clear the other chamber and why I am predispositioned to doing it on the “bench”. I have wondered why I just couldn’t do it mounted as you suggest. Then they went into a bit of a fuss on tapping the cylinder to release more bubbles, then pump some more….repeat until no more bubbles. What is enough? Am I overthinking it?

Vignette's avatar

Thanks @lucillelucillelucille The lower housing unit on the outboard is next. Whaddya got for me on that?

lucillelucillelucille's avatar

@Vignette -Is it outboard or an inboard/outboard? Replace your water pump….

Tropical_Willie's avatar

Is it a single piston brake system and non disc brake system on a 1966 Ford product?

Vignette's avatar

@lucillelucillelucille I did mention it was outboard

@Tropical_Willie It is a single piston and drums all around.

Tropical_Willie's avatar

I think of all the VW Bugs, 1960 through 1970, I did about 20 rebuilds or replacements of master cylinders; always did bleed on car (Single piston non-discs).

lucillelucillelucille's avatar

@Vignette – Make sure the lower end seals are good,replace the water pump if applicable and remember always use a little Vaseline around the pump.

Also bring oars on your maiden voyage as I didn’t give the lecture on transom mounts or drain plugs.

kritiper's avatar

It helps if you have a kit for bench bleeding.
Mount the M/C in a vice. Install the tubes from the kit into the brake line fittings, or sockets, and place the other end of the tubes into the reservoirs of the cylinder, making sure the open ends of tubes are below the surface of the fluid. Fill the reservoirs with clean, dry, fresh DOT 4 brake fluid and depress actuator rod to force fluid through the cylinder, tubes, and back into the reservoirs. Do this until all air bubbles are gone. Remove tubes and install cover. Install cylinder in auto and bleed brake cylinders starting with the one closest to M/C and working in sequence to furthest brake cylinder. Be sure to check the M/C often to make sure it doesn’t run out of fluid!!!

Vignette's avatar

@Tropical_Willie Kinda why I asked this as I have seen both schools of thought so far. It is still in the box so want to do this once and do it right.

Vignette's avatar

@lucillelucillelucille Oars are for row boats. If we stall out I will simply hop in the water and do the breast stroke and tow the barge back to shore.

lucillelucillelucille's avatar

@Vignette What if your boobs get tired?

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