Bench Bleeding

[Rampage]

Can you bench bleed The master cylinder without removing it from your car?

 

[95' regal gs]

In reality no, if the master has air in it then the only way to get it out is to bench bleed it. The reason is most master cylinders have a upward inclanation, the front is higher than the rear. Air will obviously travel towards the highest point which would be the very top front of the master, very far from the ports. The purpose of bench bleeding is so that the master cylinder is level, allowing the air to get to the ports and out of the system.

 

[Rampage]

Ok Thanks-- That makes sense to me. I guess it's also easier to remove the master cylinder than jack the back of the car 2ft off the ground...

 

[jmd]

Theoretically yes. Get a spare lid. Get old lines or the bleeder fittings and run the lines through the lid and submerse the loose ends under fluid. With a vaccuum booster car this works fine although as posted above you'll want to watch fluid level depending on application & master cylinder. Stock vac. booster G-bodies aren't too bad on the angle of the master.

 

[95' regal gs]

But, if your going to do that you might as well remove the master cylinder (you'll have the lines loose anyway), what's two more bolts? That's just my opinion, I can not stand having any air in the system, I like that pedal to be perfect. Just make sure you use a fender cover and have a bucket of water on hand in case you spill. When you bench bleed it, route the lines back into the resivour but make sure they are as far away from the fluid ports as possible. This will keep any air that is pushed out from going right back inside. When you stroke the piston use slow, steady strokes. Don't pump it or you'll foam the fluid and make it that much harder to remove that air. After you've slowly stroked it 15-20 times, lightly tap the side of the master with a small wrench to free any small bubbles that may have stuck to the inside. Wait fifteen minutes and repeat. When you put it back in the car, leave the lines attached untill you absolutly have to remove them, make sure the lid is on. Reattach the vehicle lines and snug them down. Have an assistant slowly stroke the pedal and then hold it down. Crack the lines loose and catch the fluid in a sutible container. Do this twice on each line.
This is the way I've always done it, but as I said, I cannot stand a mushy pedal.

 

[Roger]

My driveway has enough slope to totaly negate any concerns of mc tilt. I bench bled mine in the TR.

 

[95' regal gs]

If it works for you, why not? I've done plenty of things not quite by the "book"
"Dont hit that starter with a hammer" "Never exceed 40psi to seat tire beads" "Never hook jumper cables to your testicles" (Just kidding about that last one, kinda)

 

[zeus87gn]

Every master cylinder I have ever bench bled I have done on the vehicle.
Including a couple of PowerMasters. Never had a problem.

Never really gave a thought of jacking up the rear of the vehicle to make the cylinder level, but that is a fabulous idea. I will try it next time and see how that works. Thanks for that.

Z

 

[Rampage]

Thanks for all the advice. I'll give it a shot and see what happens...