Packard Forum Index » Post-War (1946-54)

Hey Guys,
I had installed the, "Master Power Brakes", booster and cylinder a whlie back. And I also ran all new brake lines, plus I have new wheel cylinders. So, yesterday I decided it was time to bleed the new system in. Well at that point I realized I hadn't bench bled the master cylinder.

Went to Autozone and picked up one of those, "MightyVac" hand bleeders and began bleeding the master. I connected two lines at the outlets of the master, with the pump hooked up to one of the lines. I proceded to pump till there were no more visible bubbles coming from the master. From there it was to the "rear passenger" side of the car to loosen the bleeder screw. Hooked up the pump and began to pull fluid. Yet, the vacuum gauge shows it is not holding vacuum very well.

So today i've been out there pumping, and pumping, and pumping. All I'm getting is alot of air, and very little fluid. I've gone along the lines, and there appears to be no leaks. The flares are, "manufacturer" done. SO WHAT IS THE PROBLEM!?!?! Did I not bleed the master properly? Is air getting in somewhere I don't see? Do I just need to keep at it?

P.S., When I push in on the pedal, air is forced out along with some fluid. Yet, it doesn't appear that any fluid is being drawn back through the line when I let off, doing it the one man way.

-Garrett

I bench bled the dual MC on my MPB setup on my 55 Pat and never had a problem.

However, I had a problem similar to what you are describing on my 1963 Tempest that I converted to front disc brakes with dual MC, but not power. I finally traced the problem to too short a pushrod between the pedal and the MC. I lengthened it and that fixed it.

Craig

Need to keep at it, and some grease around the bleeder where the hose goes on helps, and even tefloning the threads of the bleeders has been recommended for mity vac so you're just not sucking air around the threads.

I've been having the same issue with a 71 pontiac i'm working on using a mity vac with new master, booster, all new lines hard and soft, new calipers and new wheel cylinders, and new prop valve. Everything i have is top notch quality, but the bleeding has been a real PITA. I really think the mity vac is just loosing it's charm, and i may get some of those bleeders with check valves where you just pump the crap out of the brakes with them loose until they spit only fluid...no opening and closing bleeders.



Bleeders

I've had a similar issue so suggestions welcomed here as well.

My master was bench bled but in tilting into position and connecting tubing, can't rule out not getting air in again. Also not convinced in a drum system those vacuum setups do anything but draw air in from an adjacent cylinder. I also pumped a considerable time with one without much of anything happening except getting a tired hand. Suspect there is probably less resistance pulling air backward thru the piston cup next door than pulling the fluid.

I changed the bleed screws to Speedbleedsspeedbleeder.com/ for a one person operation. Bought them at Napa and will try doing front and rear wheels at same time when I get back to the project. That should eliminate any chance the dual master piston is floating to a supposed ruptured line position and messing things up.

What about trying a gravity bleed? Put a clear plastic hose over bleed screw at furthest corner going into a jar with a couple of inches of brake fluid in it to cover the hose end. Then fill the master, open the bleed screw and add fluid to the master until air bubbles disappear in jar and close screw, then go the next furthest away and repeat the process. May need to repeat sequence.

It will probably require a helper seeing where the master is located.

I have always been able to bleed the entire brake system by my self without using a power bleeder or hand pump. I bench bleed the master cyl, and then install wheel cyls and brake lines. Make sure top on M/C is secure on a full m/c resevoir.......open all the wheel cyl bleeders and pump the brake pedal until you see fluid squirt out of one of the w/cyls.........close that bleeder and keep pumping until another wheel cyl squirts.....and so on. Also keeping an eye on the m/cyl resevoir to not let it run dry. When fluid has squirted out of all four bleeders, and all 4 are closed....go around and adjust the brakes on all 4 wheels....9 out of 10 times your pedal will be up and hard. Assuming m/cyl rod is adjusted (if appropriate) and all fitting, and hoses are tight. You just shouldn't need to buy anything to accomplish this task. My I hope this helps.

Your master cylinder has check valves in it to hold a light pressure on the wheel cylinders, if indeed the master cylinder is for drum brakes. These valves make it very hard to vacuum bleed a system, and there is always the problem of air leaking in around the bleeder screw threads. Air is a lot less viscous than brake fluid!

Bleeding brakes is easy as pie once the master cylinder has been bled--sounds like you did that just fine. NO expensive equipment is needed, just a jar with a bit of brakefluid in it, and a length of rubber hose that fits well to the bleeder; the other end just submerge in the fluid in the jar. Then its just pump the pedal slowly til you have no bubbles coming in the jar. You might get some small ones because of air leaks around the bleeder, but no major eruptions. No need to keep opening and closing the bleeders--that's why we submerge the hose.

If the master cylinder is stroking properly, ie pushrod adjusted correctly, it usually takes about 12 strokes to get the right rear clear, then maybe 5 for the left rear. The fronts around 8 on the right and 5 on the left. I include this count so if you've pumped 50 times and one wheel still isn't bled you'll have a hint.

I've bled 100s of Packards using no more than a plastic peanut butter jar and 2 feet of hose. Alone.

Dear GearRat:

When they build cars they don't bench bleed the master cylinders. However, I have never seen a video on just how they fill the system at the factory. When the cars come off the truck there is no evidence of brake bleeding anywhere.

The suggestions about the booster pushrod length are instructive.

I would take one of your old wheel cylinders to NAPA and buy a set of Speed Bleeders. I have the NAPA number around here somewhere if they are ignorant. These will let you bleed your brakes without alot of headaches.

From post 1 above -Quote:
"I had installed the, "Master Power Brakes", booster and cylinder a whlie back. ...
... hand bleeders.... I connected two lines at the outlets of the master..."

Are we to assume that hte Master Power BRake cylinder is a DUAL type master??? More specifically it has a TWO brake lines comming out of it. A line at/near the FRONT of master cylinder and a line at/ near the rear. AND that the FRONT line feeds the REAR brakes while the rear line of master feeds the FRONT brakes AND that the car has DRUM brakes on ALL 4OUR wheels????

Tim Cole Quote:

Like I said above, that was the problem on another "custom brake installation" that I did. IMO, it's worth checking the geometry first before pursuing other avenues.

Craig