I put this together 10 years ago or so but used it today so I thought I would share. There is a commercial version for sale but it wasn't worth it for me. I was sick of using all the cheesy one man bleeding systems that didn't work sold at the auto parts stores. Speed bleeders, vacuum pumps, plastic containers with magnets... all a waste of time money and sanity.
The pressure bleeder works with abs, can allow bleeding of calipers in any order, will bleed calipers that have the bleeder valve upside down and will bleed brake systems with the master cylinder below the calipers and other crazy setups. If you are using expensive brake fluid for your track car you can bleed the very minimum required by the tech.
This is a very simple repurposed of a garden sparyer, a tire pressure gauge, some clear vinyl tube, a flat piece of rubber, a brass barbed fitting (or the tapered cap from some rtv if you are really cheap), a brass "T", hose clamps, some scrap metal/nuts and bolts. I payed under $20 for the stuff I couldn't find for free.
The bug sprayer hand it's plastic wand/hose removed to be replaced with tubing. Tubing is malleable when heated with a small flame and will stretch to fit other similarly sized fittings. I spliced a " T" in the tubing next one end goes to the tire pressure gauge (with one way valve unscrewed and discarded), the other end goes to the master cylinder so make yours long enough. New brake fluid goes in the bug sprayer, make note of where the straw sits in the bottom of the sprayer tank. If you tip the tank and run the fluid to the bottom you might end up sending air up the straw.
Next is the pressure cap, these are also for sale, separately. Mine was harvested from bits of a lawn mover on the curb that I cut up and welded together as shown. (One could use plumbing solder and a propane torch if going cheap. ) the shackles on the sides of the brake fluid resivor just pull down the flat piece of steel and sandwich the rubber gasket to the master cylinder top. The design pictured will work for almost all sizes of filler neck even radiators ( also very handy for finding leaks and bleeding cooling systems at ambient temperature. Just get a new sprayer and tubing to avoid contamination). On the side of the tubing that sits in the brake resivor is the barbed brass fitting ( or tapered rtv cap) this just keeps the tube from getting pulled out and to make a seal.
Hopefully the photos cover what I missed in the description if not just ask.
I pressurize the tank to 10 psi or so then just turn the factory style bleeder screws until the brake fluid changes from yellow to blue and that's it.
Good build.I plan to build another simpler version than my last.I made one for reverse bleeding.Slowly adding brake fluid through the bleed screws up to the master cylinder,displaces the air and forces it to the top.Systems where the master cylinder is lower than the calipers, or wheel cylinders,works best when the fluid is pushed back through the system,from the master cylinder.The reason is the same,push the air out the highest point.
Exactly. This is how I've always bled the brakes in my airplanes and how I'm planning to do so in my project car. From the calipers up to the master cylinder. I usually cobble something together with a sufficiently large oil can (new, of course) and a length of clear tubing.
When doing the first fill on a new system (as with kitplanes and cars), old fluid is obviously not an issue. I just squeeze the oil can trigger to pump new fluid up through the caliper and lines to the master. Once the master's drain holes are covered, tighten the bleed screw and go on to the next one. When all are done (my Ultima GTR has eight!), top off the master if necessary and it's good to go.
Changing fluid is much the same, though with the added step of removing the old stuff from the master with a turkey baster until all the lines are filled with the new fluid. The only real complication is if you're changing fluid types. In that case, I'd want to do a pressure flush from the master and force the old fluid out from each bleed screw until all the lines are clear. At that point, I'd fill it with the new stuff as if it were a new system.
When I bleed normally,I use a hose into a clear plastic drink bottle.When I reverse bleed,I use a large syringe to suck down the old fluid, as fresh fluid is pushed up through the system.I have found reverse bleeding to be faster,cleaner,and easier overall.Adding to Kbalch's statement,in aircraft,you don't want something as damaging inside an aircraft,so less mess the better.I was a pilot and aviation line service tech.When I wasn't managing aircraft,I was in the grease with the mechanics.Before that I was an auto mechanic and industrial mechanic.I have a thing for all things mechanical.It's better if it has an engine.It boarders on obsession.Can anyone recommend a 12 step program.
I am not certain which way the air in the fluid goes with the bug sprayer it may still rise to the highest point. there is a pocket of air that stays in the fluid reservoir. I use a vinyl clear tube and clear glass bottle on the drain side too. Ido remember seeing air bubbles when the air bleeder valve lets( air getting in past the threads) them in while flushing/bleeding but not otherwise.
I will have to watch out for physics professors and see what they can clarify on the matter.
it is great to see how others address the same job and compare ideas
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