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Thu May 14, 2020 1:47 pm

I have been searching and reading, have read about bench bleeding but cannot find out HOW TO? Step by step procedure. thanks

Thu May 14, 2020 2:16 pm

Connect the circuit with a hose to the reservoir. Pump it with a rod or screwdriver until no air comes out. Do it to all circuits. I do it one by one and plug each as I go.Dont push until it stops it may damage insides.

Thu May 14, 2020 3:24 pm

Thanks Jason, as always u said it plan n simple.
Thomas

Fri May 15, 2020 7:01 am

During the installation of hundreds or thousands of MCs in my life, I remember bench bleeding about 3 of them.

Fri May 15, 2020 8:32 am

Bruce, I understand what your saying, but at many attempts to get a pedal. I felt the only thing left to do was MC. I got many mixed messages.

Fri May 15, 2020 8:57 am

Tom,

I too have long heard about "bench bleeding" a master cylinder. I still to this day have never done that when installing master cylinders. But lately I'm having issues with the dual circuit master cylinder in my '67 Transporter. and wonder if air might still be trapped in there. I've searched "bench bleed" on Youtube and have viewed several different videos on how to do it mounted to bench vice, and to some degree it makes sense and I'll probably try it out someday. But I noticed that in lots of master cylinder listings in Wolfsburg West's website they often post a warning:

**PLEASE NOTE: A power bleeder must be used when installing this master cylinder. This is necessary to fully evacuate air from the unit.

I just wish that they would post a illustrated description of how to do this, what equipment to buy that works well on old VWs, etc.

So then I watched more youtube videos of how to use a power bleeder tool which pressurizes the entire sealed brake system to do this on assorted automobiles. One of the nicest advantages seems to be that using a power bleeding set-up makes bleeding brakes a one man job. I always cringed when I would have to ask my wife to sit in the VW and pump the pedal for a while.

Can anyone out there share your experiences with "bench bleeding" a master cylinder and especially "power bleeding" a old vintage VW hydraulic brake system, especially commenting on what system you bought and why, did you have to modify the tool system at all to work on a old VW and perhaps how you modified the tool system or parts? It seems to me that you almost certainly need to have an extra VW or ATE brake reservoir cap and modify it with pressure fittings and a hose so that you could then pressurize the system for such bleeding... I hope someone can share their knowledge and expertise.

Bill Bowman

Fri May 15, 2020 9:01 am

I used one of those Mighty-Vac things to do mine when I put discs on the front. Once I had a good seal on the reservoir, it worked like a champ. One-man job and an easy one at that.

https://www.amazon.com/Mityvac-MITMV8500-Silverlin...amp;sr=8-3

Fri May 15, 2020 9:58 am

Here is a pretty good review of a power bleeder system that the reviewer bought and used to flush a Honda, but you get the idea. And do not use teflon tape on the bleeder valves, the poor guy got roasted in the replies about that. Otherwise, he covered cleaning, safety and function pretty well. If something like this unit could be adapted to a VW tight sealing ATE reservoir cap with hardware store style fittings and hose it might be great.

https://www.youtube.com/watch?v=Ej7tZEBbqrI

Bill

Fri May 15, 2020 12:05 pm

You can make one really easily. Take a cap and put a valve stem in it. Use a bike pump. I wouldnt put more than 2 lbs pressure.

Fri May 15, 2020 2:49 pm

So Jason, let me get this straight
You take a jar remove the lid,
Drill a hole in it and install a valve stem?
Pump air thru valve into the jar (bike pump)
Capture air, then what?
Ok here is something that I was told long ago,by a certified German VW mechanic.He told me bleeder valves are a 1way valve and dont take air in. Eliminates the 2nd person. To be honest it has worked for me many times.....i make certain that bleeder hose is sumerged in brake fluid in container.
But this time I cant get a pedal after trying everything 3 times over. In my 67 sedan .
??????? So Im at a complete lose.
New shoes german
Drums turned
New cylinders german
New Master german
Shoes adj.up against drums,bled
Adj shoes till slight drag,bled
Opened MC pumped pedal 2 ×'s to get out any air.
Went back and bled all 4 corners 4 times.
Same at pedal a small amt of pedal.

Sat May 16, 2020 8:06 pm

2 things on this:

#1-I used to use the Motive Products Power Bleeder, It worked ok, but I just always got a 'better' brake pedal with the 2 person, one pump, one crack the bleeder, the old fashioned way.

#2-I bench bleed all the Master cylinders I install. Just one less thing to have to deal with once the M/C is installed. Real simple to do, mount the M/C in your vise, fill the reservoir with fluid, I run hoses back into the reservoir from the outlets, and then push in the M/C piston, slowly. Then just mount it in your Bus, and start at the right rear, have a buddy pump the brakes and then hold, crack open the bleeder, let it bleed out. repeat. I have an old gatorade plastic bottle with a hole cut in the top and a clear hose going thru it that slip over the nipple on the bleeder, so I can see the air bubbles and to not make a huge mess.

Sat May 16, 2020 9:28 pm

Total novice here, first time doing this, but my experience was like others here have said.

I recently bench bled a dual circuit master (from WW that mounts to a split without a mounting adapter) on my bench. One circuit needed the proportion valve removed. It was removed months before the bleed, but I could tell which one had it because the small BB could be seen thought the outlet hole.

Anyway, my good buddy had a homemade kit he let me borrow. It is basically 3 hard line stems that can be screwed on the the master about 3 inches long and have clear plastic tubing that’s long enough to go back into the filled fluid reservoir. I had this all set up on my vice and used the brake pedal yoke and adjustable piston to pump it with. I had that off to clean and descale the rust and it’s end won’t scratch the barrel of the master.

He said it could take 20 pumps or 200.....the open circuits without the proportion values closest to the piston cleared first right away but the rear wasn’t doing much. I fiddled with the lines and poked the proportioning valve ball with a wire and kept pumping and a little drip came out. Then I pumped it more and break fluid shot across the entire bench 4-5 feet. Thar she blows! Put the metal line and clear tube back on the reservoir and pumped out the rest of the air.

I was them able to mount the master with the short tubes on and swap them one at a time without much leaking but some running down my arm of coarse. Pre mounting master and bending of lines on the vehicle is critical. We didn’t have any issue charging the rest of the lines from there and believe I surly could have if not cleared the master on the bench first....

Sun May 17, 2020 5:01 pm

Figured you were bleeding a bus, in the bus forum. I have an extra bus reservoir cap with a air compressor end screwed in. You can also use a valve stem. Connect air hose with like 2 lbs on it, anymore can pop the cap or reservoir off. Open the bleeder. The pressure will push the fluid through. Keep it full or you'll push air into the lines. Make sure pedal isnt pressed. Master draws fluid in at that position. Also make sure its dry air. Brake fluid absorbs moisture.

I’ve tried the suction kind but it always leaks at the bleeder.

Sun May 17, 2020 5:57 pm

I decided to go for this 3-liter power bleeder system made by Schwaben that comes with two Eurpopean 45mm reservoir pressure caps that fit and screw onto the typical reservoir that our Buses use.

https://www.ecstuning.com/b-schwaben-parts/3-liter-premium-european-brake-bleeder/007237sch01aktkt/

I watched a few videos of it in action, and the quality looks high vs. other cheaper but similar units.

https://www.youtube.com/watch?v=edShjYeqKmY

I've never "bench bled" or "power bled" a brake system before, I've only done the two person pumper and bleeder methods, so this will be new to me. Sure looks easy and is a one person operation which will be handier. I hope that when I set it up and put it to use that I can report easy and successful results! I'm not sure yet whether or not with this power bleeder system if I'll need to "bench bleed" the MC first or skip it and just power bleed the entire system. I'll try to remember to take a few photos along the way... If anyone has used this type of power bleeder please share any of your tips on using this on an old Bus brake system. Thanks!

Bill Bowman

Sun May 17, 2020 9:56 pm

I believe the parts sellers now recommend using the fancy equipment because they got tired of beginners calling and complaining and blaming because they pumped the pedal without adding fluid before going dry in the rsvr. But ForEvers evryone just bolted in the m/c add fluid and pump pedal some and keep adding fluid.

I like a mayo jar with hose up to the bleeder and I can see what is happening even the rt rear. The hose end stays in fluid in the jar so if flow reverses it won't pull air. seems to work. :arrow: simple methods for simple times for simple cars. the beauty of these types.

Mon May 18, 2020 9:22 am

Okay, I am a mechanic with over 30 years experience. I have bled all kinds of brake systems in all kinds of cars, and all of them are easier than a vintage VW. So, it's alright to admit having trouble.

Most traditional cars (firewall mounted mc) you just bench bleed the master, gravity bleed each wheel and then pop (two person method) bleed each wheel and you're done.

In a Bus the master is at the same level as the wheel cylinders, so gravity bleed doesn't work. Bench bleeding the master is recommended, but when you install it, it will drip all over you. Not nice, even on a hoist.

A power bleeder works the best. Air pressure pushing fluid through the system at low pressure and high volume of fluid ensures all air is out of the system. The problem with a home-made version of this, is that you are only pressurizing the amount of fluid in the reservoir. This method can easily run up to 2 litres of fluid through to clear the air properly.

A vacuum bleeder also works well for the first bleed only. It can help get fluid through the system, but then you must pop bleed it after that. The vacuum bleeder can pull air in past the cups in the wheel cylinders and just be adding air to the system.

For the 2 person method without a bench bled master, I like to install the master completely and fill it up. (if you have a gerbil feeder bottle full of brake fluid it will not run dry) Have one person work the pedal and the other loosen the brake lines at the master. Crack the lines, press down the pedal, close the lines, lift up the pedal. Do this til you get no air spurts. Then bleed each wheel cylinder with the same method. Starting at the closest wheel (open bleeder, press down pedal, close bleeder). Once you have fluid to all 4 wheel cylinders, start at the furthest wheel and begin to pop bleed them (traditional pump and hold method). This should clear all air from the system.
Now there will be some of you that want to catch and reuse the fluid. I would not recommend this unless all of the system is new, fluid is cheap...a wrecked bus is not.

Hope this helps a bit.

Gordo.