Power Bleeding & MC

[JackIIA]

Has anyone ever used a power bleeder to bleed a new system (most importantly a NEW MC)?

I can bench bleed if needbe, but trying to avoid the mess.

Read on some other forums a bunch of opinions for and against.

Just curious if any real world experience with our trucks with a new MC not previously bench bled. Thanks

[TravelinLight]

I used one on a single circuit system on an 88 with great success. I picked it up from BP at the time but assume our hosts have some as well.

[cedryck]

By power bleeding do you mean forcing fluid into the master fluid holder, and forcing it out through the bleed screws? If so, that is a very practical way of bleeding. I have had good experiences with that but depending on what kind of master you have, it can be an ass pain, some say raise front end of car, some say bleed the master on the bench but then you still have to get it into the truck, heard some say loosen the outlet tube at the beginning to let air escape from the master then tighten and bleed regular, this makes sense to me because the CB master has a large bulb on the end and that seems like a place where air is trapped.

[64Blue]

I am going to be doing this tonight, as well... preferably it works with the method of loosening the pipes at the MC to get the air out first....

Also, I did discover that when buying the PLC 454 master cylinder (Dual circuit 88") from our host, it's not the one that has the "slanted" top on the reservoir (pictured here http://www.roversnorth.com/ProductDe...e=0&eq=&key=it )

rather, it looks a lot like this one for the 109 (pictured here http://www.roversnorth.com/ProductDe...e=0&eq=&key=it )

apparently, the only difference is the diameter of the piston on the master is 7/8" for the 88" and 1.0" for the 109". I thought there might be fitment issues of the reservoir, but preliminarily, looks that it will fit... will update once I install it.

[pitchrollyaw]

Over the past ~4 years I put new M/C's on my SIII, 90 and TR6 without bench bleeding and using a Motive power bleeder. I do flush a lot of fluid through though. Great results.

One caution, if you replaced the M/C with a new production one, check to ensure that the actuator rod from the booster is adjusted properly for the new cylinder. The new production M/C's may be very slightly different and require moving the head of the actuator in or out, otherwise causing excessive pedal or dragging brakes...ask me how I found out..

[fly cubs]

I'll throw in another vote for the Motive Power Bleeder- works great and is the easiest way to get the brakes bled correctly. I did mine with a new MC and slave cylinders. Even used it on the clutch with great success.

[mrothman]

HI
Did you have to buy an adapter tp fot the M/C if so do you have a part #? I have a 64 IIA 109 not with the original metal can fluid reservoir but a plastic Girling reservoir. My pedal goes 90% to the floor on the first pump and then after 1-2 pumps is 50% nice and firm have checked for leaks, clamped off rear hose and pedal very good clamped front two flex hoses no change all adjusters working new drums have bleed them to death no change and also just replaced the rear flex line no change

[mrothman]

I have a 64 IIA 109 with original style CB master brake cylinder. Love this truck but the brakes are horrible. Replaced all drums,checked for leaks, bled them to death but the pedal still goes 90% to the floor on the first depression then gets higher and firm after 1-2 depression. Pressure bled, jacked u p front,jacked up rear bled again, pressure bled again, replaced the rear flex line hose, adjusted shoes to lock up and pedal still goes to the floor, clamped rear flex line and pedal only goes down about 10% and firm clamped front two flex lines and no change,, bled again no change. The only thing left is to change the master or i still have air?????? Any advice would be welcome. I am a Series Rover owner for 30 years but these brakes are making want to bail out..........

[lumpydog]

Try putting 4-5 wraps of plummer's tape on the bleeder valve threads to prevent air ingress while they're open.

Also, adjust the shoes so they are as far away as possible from the drum (vs lock up), to get the least volume in the wheel cylinder and make it harder to trap air.

With the flex lines clamped, does the pedal maintain firmness after 20 minutes?

With the CB, having the front end raised is the right approach if you suspect air is trapped there.

[clearcut]

I added speed bleeders

Not sure if the host carries them

speedbleeder.com

Let's fluid out and not air in. Check value

The cap on my 1967 109 is 45MM. My pressure bleeder came with this size.

josh t

[mrothman]

Thank you. I have not tried to leave the rear clamped that long...what are the ramifications of this test one way or the other??. We have used a pressure bleeder have raised the front and the rear. Wondering still if the MC is bad???

[blueseriesii]

I found on my Series II with the CB master cylinder that despite having bench bled the MC the only way to get fluid to move into and through the system was by using pressure.

When bleeding if there is much air in the lines there's not enough suction developed at the MC to draw fluid through it when the pedal comes back up, the air just expands and contracts. This is true even if the bleeder screws are closed.
I made up my own pressure device using a portable air tank at 12 psi with a quick release air fitting snapped on to a companion fitting on a gasketed scrap of wood I clamped onto the reservoir. One does have to remember to monitor the fluid level so you don't push air into the system.

I have used the technique of driving the front end up a gravel banking for bleeding, trying to coax the last bubble of air out of the back of that MC. Searching for a better method I drilled and tapped a 1/4" hole on the back side of the nut at it's highest point. I filed the surface of the nut smooth and used a 1/4" bolt and copper washer for a final seal. Loosening this just a bit while there is some pressure in the system will drive out a little fluid AND the last bit of air, hooray.

The amount of pedal travel is of course affected by any air in the system but even with an air free system it takes a certain amount of pedal travel just to bring the shoes up to where they meet the surface of the drum.

Unless the shoes have very little wear and are adjusted very close to the drums much of the pedal travel is taken up simply in moving the shoes closer to the surface of the drum. When the pedal is released again to "pump" the brakes for a second time the strong set of upper return springs immediately pulls the pistons back into their bores and you're back where you started from with long pedal travel.

For my Series II, I removed the upper set of return springs and rely only on the lower set of springs. This allows the shoes to just barely float on the surface of the drum.

It also prevents the pistons in the wheel cylinder from being pushed back into their bores every time my foot comes off the pedal. I now I have a very stiff pedal with only about 2"-3" travel, first time since 1974!

I hope to put this on the road soon and I'm quite sure the brakes will not drag enough to heat up. If so I'll add a set of very weak springs.

Hope this helps