Brake Bleeding

[rboltz]

I haven't bled brakes for 40 years or more and my memories of that are not good. I just read some internet posts about it and am curious about the vacuum bleeders. Also, about "bench bleeding" a new master cylinder.

Since I won't have any reliable help to bleed the system, after adding the dual master, I like the sound of the vacuum bleeders I've read about. But, there are also some bad reports about them. Looks like you either love them or hate them. Any comments out there?

As for a new master cylinder bench bleeding, is there any reason you must do it in a vise? All the instructions say to do it that way. Why not just mount it, install the bleed kit, and use the pedal to bleed it? Seems easier and less mess.

[randygar]

I've always bled them in the car. no problems yet. just remember light taps on the pedal, don't stomp on it, or you'll blow the little plastic plugs out the side.

Vacuum bleeders are pretty easy to use, but getting a hose on it a bit annoying given the limited room between the backing plates and the suspension. Just loosen the bleeder nipple (use a closed-end wrench or a socket, especially if they haven't been out for a while!), stick the hose on from the vacuum bleeder, remove the top from the master cylinder and top it off, then squeeze the handle on the bleeder until clean, bubble-free fluid comes out.

The other type of single-person bleeders are just a check valve in a hose, which work too... step on the pedal while checking what's in the hose every few presses.

Make sure to keep the reservoir topped up... if it runs empty, you'll have to start all over!

--Randy

[randyscycle]

After bench-bleeding the master cylinder, then just gravity bleed the system. With the M715, the master cylinder is high enough, that I gravity bled mine just fine. Just open the bleeder screws at all four wheels and keep the master cylinder full, until straight fluid runs at all four wheels.

The vacuum bleeders work OK, but I find that they won't always pull enough to get all the air because its next to impossible to seal the threads around the bleeder screw when its loose enough to allow fluid flow.

You can also make a pressure bleeder out of a pump-up sprayer like used for applying chemicals to the yard. You'd have to make an adapter for the top of the master cylinder too.

[fng]

I actually bought one from Harbor Fright for about 20 bucks. It was the most expensive looking one they had. It took alot to get one of the fronts done but it worked. It would've taken hours by myself so I got the wife to help.

[Warthog]

Hey ya go.

Poor Mans Brake Bleeder

[phoenix]

I made a preasure bleeder from a 3 inch pipe that I welded some end caps onto and then put a plastic line coming out the bottom of it. The top has a ball valve and is also used to fill the pipe with brake fluid . I use preasure from my air compressor to push air into the top and that pushes the fluid down and through the plastic hose. I connect the hose to the brake bleeder screw.

I usually have the master cylinder only 1/4 -1/2 full so when the preasure bleeder pushes the fluid through the line, it fills the master. I have used this setup a couple dozen times now and it works perfectly and I can do it all myself.

You have to use it just right though and preasurise the canister slowly by opening the ball valve, then when you think you have enough fluid pushed through the line, you need to shut the ball valve off and then unhook the air line. close the bleeder valve then open the ball valve again to allow the air to escape the canister. now disconnect the plastic line that goes to the bleeder valve.

Usually I can use 50 psi to make it all happen but I have had to go up to 90 psi once to clear a blockage in a line.