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P-30 master cylinder disassembled [message #279216]

Sat, 06 June 2015 14:53

wally

Messages: 643
Registered: August 2004
Location: Omaha Nebraska

Karma: 5

Senior Member

After battling a P30 master cylinder bench bleed I took one apart to see what's in there. This one does indeed have O rings as seals along with Teflon rings. The end opposite the pedal was the booger, seemingly bubbles forever. That telescoping piston has a bunch of holes and places to trap air. how level it while bleeding may make a difference.
pics http://www.gmcmhphotos.com/photos/g6798-p-30-master-cylinder-disassembled.html

Wally Anderson
Omaha NE
75 Glenbrook

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Re: [GMCnet] P-30 master cylinder disassembled [message #279218 is a reply to message #279216]

Sat, 06 June 2015 15:48

emerystora

Messages: 4442
Registered: January 2004

Karma: 13

Senior Member

Years back a very seasoned mechanic taught me to tap on the MC when bench bleeding it. He said it loosens those little air bubbles. It seems to work.

Emery Stora

> On Jun 6, 2015, at 1:53 PM, Wally Anderson wrote:
>
> After battling a P30 master cylinder bench bleed I took one apart to see what's in there. This one does indeed have O rings as seals along with Teflon
> rings. The end opposite the pedal was the booger, seemingly bubbles forever. That telescoping piston has a bunch of holes and places to trap air. how
> level it while bleeding may make a difference.
> pics http://www.gmcmhphotos.com/photos/g6798-p-30-master-cylinder-disassembled.html
>
>
>
> --
> Wally Anderson
> 1975 Glenbrook
> Megasquirt 455 port injection science project
> Omaha Nebraska
> Greater Midwest Classics
> GMCES
> http://wallyandsue.blogspot.com/
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Re: [GMCnet] P-30 master cylinder disassembled [message #279235 is a reply to message #279216]

Sat, 06 June 2015 20:23

USAussie

Messages: 15912
Registered: July 2007
Location: Sydney, Australia

Karma: 6

Senior Member

Wally,

Great photos! Thanks!

I direct everyone's attention to this photo:

http://www.gmcmhphotos.com/photos/p-30-master-cylinder-disassembled/p58095-6-bore-with-groove.html

Note that there is NO recess in the mounting flange for the OEM cup seal so even if you remake the bracket like Kelvin did there is
no place for the seal.

You will need to:

a) find a P-3 with a recess and use the OEM seal

b) install a seal at the bottom of the booster bore and a ring to center the master cylinder in the boosters bore

Regards,
Rob M.
The Pedantic Mechanic

-----Original Message-----
From: Wally Anderson

After battling a P30 master cylinder bench bleed I took one apart to see what's in there. This one does indeed have O rings as seals
along with Teflon rings. The end opposite the pedal was the booger, seemingly bubbles forever. That telescoping piston has a bunch
of holes and places to trap air. How level it while bleeding may make a difference.

pics http://www.gmcmhphotos.com/photos/g6798-p-30-master-cylinder-disassembled.html

Wally

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Regards, Rob M. (USAussie) The Pedantic Mechanic Sydney, Australia '75 Avion - AUS - The Blue Streak TZE365V100428 '75 Avion - USA - Double Trouble TZE365V100426

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