| [GMCnet] line lock [message #121323] |
Fri, 08 April 2011 09:43  |
paul h cashman
Messages: 176
Registered: May 2005
Karma: 0
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Senior Member |
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Hi,
I ,drove my Gmc over To Home Depot two Days ago,about a 4 mile trip. The
line lock was off .I noticed the GMC didn't have the Power it normally
had,at Home Depot I checked the Wheels and they were just barely warm..The
is a hill down to a Stop Sign and it is a pretty steep Hill.I stooped at
the Stop Sign and let off on the Brakes ,it should have drifted forward ,but
it did not, so I gave it some Gas ,it went about 100 Yards and the Brakes
locked down stopping me..The Brake Pedal was hard ,you couldn't push it
in..I checked the line lock and it was off,I turned it on the off and it
seemed to clear the problem.
I went Home and put a Gauge on the line lock .With the line lock off it
seemed to work OK but when I put the line lock on ,some times the was 400
psi residual pressure on the Rear brake lines.
I checked the P30 m/s if you loosened the fitting it would bleed the
pressure off.
I checked and the P30 has check valves in the primary area of the m/s
in the past a residual check valve was used to keep residual pressure ,on
the Drum Brakes.
It seems to me, that you can get residual Pressure, even if you dont have
the line lock hooked up
Since Disc Brakes dont employ Shoe return Springs ,the check Valves are not
needed.
I removed the check Valves and the m/s will not work.
I had planned to leave for Paterson early Saturday Morning but it is unknown
now.I,m really dead in the water now.
I tried to find another m/s on the Internet but it is like a needle in a
hay stack.
Later.
Paul Cashman
Riverdale Ga
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Paul H Cashman
Riverdale Ga
1978 Transmode
1975 Corvette
1978 Beetle Convertible
1989 Harley Davidson Sportster
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| Re: [GMCnet] line lock [message #121338 is a reply to message #121323] |
Fri, 08 April 2011 16:26  |
Neil
Messages: 271
Registered: July 2007
Location: Los Angeles and Magalia, ...
Karma: 1
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Senior Member |
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That is why I would not consider line locks a solution. In my past, I have used them on off road cars and have to crack a bleeder to get the brakes to release.
Neil
76 Eleganza now sold
Los Angeles
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| Re: [GMCnet] line lock [message #121347 is a reply to message #121323] |
Fri, 08 April 2011 19:38 |
MikeT
Messages: 225
Registered: November 2009
Location: Marine City, Michigan
Karma: 0
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Senior Member |
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I bought a new master cylinder at NAPA last fall. Don't have the parts directory handy but it was new and about $30.00. Maybe someone can weigh in with a part number. I know Jim Bounds has the part number because that is who I called.
What is a line lock?
Mike Thomas
Marine City, MI
77 ex Palm Beach
[Updated on: Fri, 08 April 2011 19:39] Report message to a moderator |
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| Re: [GMCnet] line lock [message #121369 is a reply to message #121323] |
Fri, 08 April 2011 23:54 |
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John Heslinga
Messages: 632
Registered: February 2011
Location: Edmonton, Alberta, Canada
Karma: 4
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Senior Member |
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Paul:
If the residual pressure valve was holding 400 psi it was certainly defective. It should only hold about 10 psi. You are right that disk brakes do not need residual pressure. That pressure keeps the lips in wheel cylinders sealed to the cylinder walls and does not allow a vaccuum situation to let air in the system. Disk brakes use a very different flexable seal that already has pressure and seals against the wall of the caliper bore. Check the secondary piston for binding while you have it apart because it also could be holding the pressure high. (However I doubt that will be a cause unless foreign material from something damaged in the Master cylinder is jamming or blocking it's return to the neutral position)
One possible problem with your non-working cylinder can be fixed with just some time on the bench. A common mistake when doing any repair to master cylinders is not bench bleeding the master cylinder. You cannot get any pressure from it unless you do. The space between the primary piston and secondary piston will not bleed unless you do it on the bench. The main bores need a lot of fluid flow to get the air out. (Hense it will not work in the system) Put Temporary hoses or pipes from the outlets returning into the reservour and pump the cylinder full strokes with a phillips screwdriver until you have no more air bubbles. This can sometimes take a lot of strokes. Maybe you will still get to the Rally. Good luck
Best regards
John Heslinga
John and Cathie Heslinga
1974 Canyonlands 260
455, Manny tranny and 1 ton, 3:70 LS,
Red Seal Journeyman, DTE, BEd. MEd.
Edmonton, Alberta
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| Re: [GMCnet] line lock [message #121371 is a reply to message #121323] |
Sat, 09 April 2011 00:57 |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
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Senior Member |
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Paul,
It is the Red Chinese workmanship causing this problem.
Just crack open the line at the prop.valve and drive it to the convention.
On Fri, Apr 8, 2011 at 7:43 AM, Paul Cashman <paulcashman@bellsouth.net> wrote:
> Hi,
> I ,drove my Gmc over To Home Depot two Days ago,about a 4 mile trip. The
> line lock was off .I noticed the GMC didn't have the Power it normally
> had,at Home Depot I checked the Wheels and they were just barely warm..The
> is a hill  down to a Stop Sign and it is a pretty steep Hill.I stooped at
> the Stop Sign and let off on the Brakes ,it should have drifted forward ,but
> it did not, so I gave it some Gas ,it went about 100 Yards and the Brakes
> locked down stopping me..The Brake Pedal was hard ,you couldn't push it
> in..I checked the line lock and it was off,I turned it on the off and it
> seemed to clear the problem.
> I went Home and put a Gauge on the line lock .With the line lock off it
> seemed to work OK but when I put the line lock on ,some times the was 400
> psi residual pressure on the Rear brake lines.
> I checked the P30 m/s if you loosened the fitting it would bleed the
> pressure off.
> I checked and the P30 has check valves in the primary area of the m/s
> in the past a residual check valve was used to keep residual pressure ,on
> the Drum Brakes.
> It seems to me, that you can get residual Pressure, even if you dont have
> the line lock hooked up
> Since Disc Brakes dont employ Shoe return Springs ,the check Valves are not
> needed.
> I removed the check Valves and the m/s will not work.
> I had planned to leave for Paterson early Saturday Morning but it is unknown
> now.I,m really dead in the water now.
> I tried to find another m/s on the Internet  but it is like a needle in a
> hay stack.
> Later.
> Paul Cashman
> Riverdale Ga
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
--
Jim Kanomata
Applied/GMC, Fremont,CA
jimk@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502
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Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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