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I watched several brake bleeding procedure videos and there are so many different ways out there on top of that I also checked my vehicle manufacturers workshop manual.

I am a bit confused at the workshop manuals advice:

  1. Connect a transparent vinyl tube to air bleeder valve.
  2. Fully depress brake pedal several times.
  3. With brake pedal depressed, open air bleeder valve to release air.
  4. Close air bleeder valve.
  5. Release brake pedal slowly.
  6. Repeat steps 2. through 5. until clear brake fluid comes out of air bleeder valve.

I fully comprehend the advise however none of the videos I watched done it like that?

I.e. pumping the pedal, holding it down, having the air bleeder valve opened to release air/fluid, closing the valve, release the brake pedal and repeat?

Most videos tend to do it in one shot, open the valve, pump the pedal, hold it down and close the valve.

What is the best way to do it?

1 Answer 1

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The ONLY way I've ever seen/heard/done to manually bleed the brakes is exactly like what the workshop manual is stating. You need to do it in the order presented or you'll be defeating your purpose. If you open the bleeder then pump, it will draw air into the system through the bleeder valve.

The only other thing I'd add, is to put the end of the clear vinyl tube into a clear bottle, by submerging the end of it in a little bit of brake fluid (have a small amount already in the bottle). By doing this you ensure air won't be sucked back up in the line for whatever reason. It is also a collection bottle for the old fluid so it can be disposed of properly.

Let me see if I can add a little bit of context to the shop manual's procedure:

  1. Connect a transparent vinyl tube to air bleeder valve.

Straight forward. It is also a good idea to crack the bleeder open, then reclose it, prior to putting the vinyl tube onto the bleeder. It's just easier to get it ready for bleeding as the tubing will not be in the road.

  1. Fully depress brake pedal several times.

Once the brakes are hard to press, then hold the pendal down. By doing this, you are pressurizing the system. If the system is not pressurized, there's no real way for the fluid to come out.

  1. With brake pedal depressed, open air bleeder valve to release air.

Whomever is helping, should keep the pressure on the brake pedal. This keeps pressure in the system. If you don't do this, you run the risk of sucking air back into the system during the next step. Once the bleeder is opened, the brake pedal will go to the floor.

  1. Close air bleeder valve.

So no air will be drawn back into the system.

  1. Release brake pedal slowly.

To allow the master cylinder piston area to refill with fluid.

  1. Repeat steps 2. through 5. until clear brake fluid comes out of air bleeder valve.

"Clear brake fluid" means two things. First that old fluid is removed. It becomes dark green in color (if not exactly green, it will be dark/murky) over time as it absorbs water. You're looking for the clean new fluid which you've put into the master cylinder at the start of this operation. Secondly, if the system has been opened for any reason (ie: new caliper installed; brake line replacement; etc), you'll have air in the lines. You'd be looking for any air which might be in the system to be removed.

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  • In regards to Step 2. when doing this for all 4 brake lines. The pedal will become hard after a few pumps the first time doing this for the first brake line. Should the ignition switch be turned ON to "reset the pedal hardness" for the subsequent lines? Or is that not necessary?
    – Dave1UK
    Feb 6, 2023 at 11:38
  • I've never seen old fluid go green before, dark mucky brown when it's really overdue for a change, but not green. Not nitpicking, just curious if it might be a, for example, Europe vs North America, formulation difference where one has some sort of indicator in it. Regardless, old vs new brake fluid is pretty easy to spot!
    – jovisg
    Feb 6, 2023 at 11:55
  • @Dave1UK - No need to run the vehicle. You're not relying on vacuum assist to do what you need to do. When pumping the brakes, it should become fairly stiff after first or second pump. Feb 6, 2023 at 12:23
  • @jovisg - I've seen it either way, but primarily green-ish in color. (Maybe it's my slight brown-green color blindness coming into play? LOL!) Brake fluid should be changed every two years. It collects moisture over time. As it collects moisture, it becomes dark and murkey. No matter the color, it definitely isn't a clear light amber liquid anymore as it looks when it comes out of the bottle. As far as I know, DOT3/4 fluid is pretty much the same no matter what part of the world you're in. I did put in a slight edit to clarify. Feb 6, 2023 at 12:27

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