Hibernating for way too long!

[greg jankowski]

Greetings, I'm a lurker coming out from under the trees (with pine sap to
show for it).

A major brake job has stalled out for over a decade due to my inability to
bleed rear brakes. The culprit seems to be the master cylinder(s) (new P30
Napa NMC M2219) The front discs bleeds beautify, the rear brake side
refuses to have enough pressure/flow to purge the air. I've purchased 3
master cyls so far & have tried bleeding them;

1st mounted, 2nd bench bled, 3rd pressure bled bench. All with the same
results, the front cylinder/rear brakes never get enough pressure to push
my finger off of the outlet.

Complicating the project is the scope of the project so far it has entailed
the following parts; rotors, pads, larger rear wheel cylinders, SS rear
hoses, brake shoes, all the brake lines and the 3 masters. Thanking you in
advance.

Greg Jankowski

Wheat Ridge, CO

73 23 CanyonLands

 

[Larry Davick]

Greg,

I know many have had great success with the pressure bleeding method on the coach. I’ve had good success on my cars with the Harbor Freight vacuum bleeder.

https://www.harborfreight.com/brake-fluid-bleeder-92924.html

Still others have used gravity to bleed the system. Good luck and keep trying!

Larry Davick
1976 Palm Beach
Fremont, Ca

 

[jerry burt]

Greg,
The one thing I didn't see you mention is the distribution block mounted on the frame directly below the master cylinder. This has a piston in it that
moves side to side to shut off the fluid to the front or rear brakes if you loose a wheel cylinder or line. That allows you to limp home with minimal
stopping ability. If it is an original steel block, it's possible that it is plugged up with crud or the plunger has moved plugging the rear lines.
HTH.
--
Patti & Jerry Burt Fresno, CA.
73 Gmc 26' Canyon Lands
77 Palm Beach - Parts Coach - SOLD
Members: FMCA - GMCMI - GMCWS
A truly happy person is one who can enjoy the scenery on a detour.

 

[LarryW]

About 7 or 8yrs ago, after installing a disc system on the mid axle, I was convinced that I needed a P30 for the extra volume. I ordered one, and
could not bleed the front part of the MC...just would not make pressure. I got 4 more of those, one after the other that would not bench bleed. On the
last one, I fashioned a levered system and was finally able to break the front piston loose from the bore. But then it leaked. Each one of the MC's
that I got (total of 5) had to be brought in from another store in their system. Each one of them had been sitting on the shelf for many years. That
P30 is no longer a hot item, so they were drawing from P30's that had been shelved for many years, and I am speculating that moisture had corroded
that front piston so it would not break loose on a bench bleed. After that experience (that BTW, I was doing out in the snow) I finally borrowed a
stock MC from a friend. Drove it for several thousand miles with no issues and a solid pedal. There are other issues with the P30 that Dave L
explained and demonstrated to us in one of his GMCMI sessions that could lead to near complete failure of the P30. If I were you, take the MC back in
favor of the stock MC. You may have to get it from Jimmy K at Applied, because they are hard to find through normal parts house channels. JMHO
--
Larry
78 Royale w/500 Caddy
Menomonie, WI.