| [GMCnet] Brake prop valve [message #277019] |
Wed, 29 April 2015 19:37  |
glwgmc
Messages: 1014
Registered: June 2004
Karma: 10
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Senior Member |
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Our 78 Royale has had a one ton front and reaction arm disks since those were first available. I always thought the stock mc resulted in very low brake pedal. It stopped really well,but the low pedal always bothered me.
Today I pulled the pro portioning valve (aftermarket brass) and found it was the pv2 meant for stock rear drum brakes. I replaced it with the correct pv4 for disk brakes and that made all the difference. Pedal is higher and hard just like it should be. I still need to watch The fluid as the pads wear, but the difference is night and day
Jerry
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Jerry & Sharon Work
78 Royale
Kerby, OR
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| Re: [GMCnet] Brake prop valve [message #277032 is a reply to message #277019] |
Wed, 29 April 2015 21:50  |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Senior Member |
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Jerry,
I suspect you may have had air in the brake lines.
As noted here:
http://www.gmcmhphotos.com/photos/aa-miscellaneous-photos/p37696-combination-valve-cross-section.html
The metering function pressurizes the rear brakes to 130 psi then pressure is sent to the front brakes, I don't think it would take
much pedal travel for the M/C to generate 130 psi.
Having "said" that how much higher is the pedal now?
Regards,
Rob M.
The Pedantic Mechanic
-----Original Message-----
From: Gerald Work
Our 78 Royale has had a one ton front and reaction arm disks since those were first available. I always thought the stock mc
resulted in very low brake pedal. It stopped really well,but the low pedal always bothered me.
Today I pulled the pro portioning valve (aftermarket brass) and found it was the pv2 meant for stock rear drum brakes. I replaced
it with the correct pv4 for disk brakes and that made all the difference. Pedal is higher and hard just like it should be. I still
need to watch The fluid as the pads wear, but the difference is night and day
Jerry
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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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