Bench Bleeding Master Cylinder, Vacuum Pump vs Pushrod

[peejay75]

Seems that using a vacuum bleeder uses (wastes) fluid into the collection cup, versus using the pushrod/pedal method that recirculates the fluid within the reservoir.

Any advantage to one method over the other?

 

[Bigblue&Goldie]

The last one I did I used one of the cheap Doorman syringe tools and it worked great.

 

[peejay75]

The last one I did I used one of the cheap Doorman syringe tools and it worked great.

Could you explain this technique, may be a better alternative than what I have in store!

 

[Bigblue&Goldie]

I feel like I did something very similar to this:

How To: Syringe Bleed a Master Cylinder | Master Power Brakes

Sometimes we get questions from folks wondering why we include syringes with our power disc brake conversion systems and how

mpbrakes.com

 

[gahrajmahal]

No matter how you bleed your master cylinder bleeding the rest of the system is where you will have issues. My Honda Ridgeline could not get a high and firm pedal until I bought a Motive Power pressure bleeder. Here is my thread on this miracle tool.

Spongy Brakes Fixed with Motive Power Pressure Bleeder

My Honda Ridgeline has suffered from low pedal and spongy brakes for a long time now and I have replaced most all of the components, calipers, new lines, master cylinder and power booster. Well, two master cylinders as one was deemed faulty. My usual method to bleed brakes is the two-man system...

www.garagejournal.com

 

[Bigblue&Goldie]

I actually just realized I'll likely be doing another master cylinder (all new booster/master/soft lines/calipers/rear drum cylinders) next week. I'm finishing off putting F-350 brakes on a Bronco after an axle swap. I won't be driving it any time soon though. My plan is to bench bleed the master with the syringe, get it installed and flush the existing hard lines of old fluid. I'll then get all the new brake components in place, and use my Speedi Bleeder to do an initial bleed. Once I get the truck running I'll re-bleed the system. My main priority is getting it all in place without running the old, dirty fluid through the new parts.

 

[peejay75]

Well, just attempted to "bench" bleed the master attached to the firewall...seems that way definitely wastes a lot of fluid unnecessarily. Next time I'll try doing it via the pedal, and using a camera to record for bubbles...(helper is unreliable at the moment)

anyhoo, after all that work, the master wasn't the problem, who knew? (me!) on to bleeding the damper next, while waiting on the slave cylinder to arrive.

(i did try using the mityvac to force fluid through the opening in the reservoir before bench bleeding, but it's not centered in there, and getting a syringe in there could be tricky, i.e. frustrating/cuss-inducing!)

 

[Bigblue&Goldie]

The problem with bench bleeding on the vehicle is the master is usually mounted at an upward angle, which traps air at the end of the bore past the furthest port. Try taking it off and bleeding it level in a vise.

 

[gungatim]

The problem with bench bleeding on the vehicle is the master is usually mounted at an upward angle, which traps air at the end of the bore past the furthest port. Try taking it off and bleeding it level in a vise.

Bench bleeding literally means bleeding it on the bench before it is installed.

 

[peejay75]

Good info, folks, thanks!

 

[Bigblue&Goldie]

Bench bleeding literally means bleeding it on the bench before it is installed.

I get that, read the post I'm responding to. A lot of people, o.p. included, use "bench bleed" synonymously with the initial bleeding of the master cylinder prior to bleeding as part of the system.