Quick Question on Brake MC Bleeding

[DaleG]

While bleeding the rear brakes (vacuum method) I inadvertently emptied the reservoir. During the process, I did not pump the brake pedal. Do I need to re-"bench bleed" the MC?

[GoDadGo]

Cap it off after you refill the reservoir and try the brakes, but I fear that you will likely have to bleed them again.
You'll know when you feel the pedal and if it is spongy, start bleeding once more.
Good Luck & Hope You Dodged A Pain In The Neck!

[Bob Cowan]

The purpose of "bench bleeding" a master cylinder is to specifically purge the air out of the piston area. If you let the MC run dry, you're better off starting over and bleeding the MC by itself, and then bleeding the rest of the system.

[JC Of NM]

I would start again.

[carlewms]

Dale,

For an additional point of reference ... I used a pressure bottle to bleed the brakes and the clutch. After fixing one leak we got a good pedal within just minutes. I used the same system to do the clutch MC. I as I recall we pressurized the master cylinders first until we got a solid stream off the cylinders and then did the brakes and clutch. The photo below is a link to the Summit Site where I purchased the system.

http://static.summitracing.com/global/images/prod/mediumlarge/mvp-0252_w_ml.jpg

[DaleG]

Thanks all. I'll just go ahead and re-bleed the MC before I bleed the rest. Now I have to dig through my wife's metal sculpture bins to locate the bent tubing I used the first time around.

[Norm B]

You could try back bleeding the rears. I use a large syringe and a piece of clear tubing that fits tight over the bleeders. Just push the fluid back through the bleeder until the master cylinder has fluid. Do both sides. Let things sit for a bit, then slowly depress the pedal a couple of times. Bleed the rear brakes normally to remove any air trapped in the top of the callipers. If the pedal is firm you should be good to go.

HTH
Norm

[johngeorge]

If you have wilwood brakes, they sell the pressure brake bleeder that threads onto the master cylinder reservoirs.

http://www.speedwaymotors.com/Motive-Products-0100-Pressure-Brake-Bleeder-Wilwood-Master-Cylinder,5790.html

[mikeinatlanta]

I disagree with the popular opinion on this. If pressure bleeding, bench bleeding serves no purpose.

[carlewms]

I disagree with the popular opinion on this. If pressure bleeding, bench bleeding serves no purpose.

I agree with Mike ... when we pressure bled the clutch (which is the one this old memory remembers better) we realized that we could have done everything at the slave cylinder end and not have to bleed the clutch master cylinder.

Carl

[DaleG]

So I could just use my vacuum system with a rubber plug (with a hole in it and a short piece of brake line in the hole) in the mouth of the reservoir, and pull fluid from the brake end? I know how to keep air from entering around the bleeders. At any point do I need to pump the brake pedal?