The Murphy Builders Site

Posted: **Sat Feb 18, 2012 2:33 pm**

I have the brass colored Matco wheels and brakes on FOKM and am having
trouble with a leak in the left brake. I have had it apart about 4
times, replaced the O-ring, pads and generally cleaned it up and it
still seems to leak from the piston area.

The O-ring I replaced in kind but it does have lateral movement along
the axis of the piston in the O-ring slot. ie: the O-ring would have to
be elliptical in x-section or else another element would be needed in
the slot to stop axial movement of the ring. The piston fits nicely with
the O-ring so the axial movement must be intentional.

The caliper housing is a PH-1 and the drawing from this website does not
show any extra bits in the O-ring slot.

http://matco.elixirlabs.com/users/matco ... akes4a.jpg

Any advice on this before I take it apart again (he says gritting teeth)
would be much appreciated.

--
Garry Wright
R-068 C-FOKM Amphib
403 931 1573
wrightdg@davincibb.net

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Posted: **Sat Feb 18, 2012 2:33 pm**

Hi Garry !

May be irrelevant, but what are you using for brake fluid ??
The Murphy factory always used ATF - NOT brake fluid. The Automatic
Transmission Fluid - from Canadian Tire, of course ! ;-) - works
great, and doesn't make such a mess of paint and hands.

Just wondered, as some O-rings may swell or leak if they get
the wrong fluid ....

Maybe you could add an elastic to the groove to keep the ring
more in place ???? :-) :-) ;-^)

.....bobp

-------------------------------orig.-------------------------
On Friday 16 December 2005 11:23 am, wrightdg wrote:

I have the brass colored Matco wheels and brakes on FOKM and am having
trouble with a leak in the left brake. I have had it apart about 4
times, replaced the O-ring, pads and generally cleaned it up and it
still seems to leak from the piston area.

The O-ring I replaced in kind but it does have lateral movement along
the axis of the piston in the O-ring slot. ie: the O-ring would have to
be elliptical in x-section or else another element would be needed in
the slot to stop axial movement of the ring. The piston fits nicely with
the O-ring so the axial movement must be intentional.

The caliper housing is a PH-1 and the drawing from this website does not
show any extra bits in the O-ring slot.

http://matco.elixirlabs.com/users/matco ... akes4a.jpg

Any advice on this before I take it apart again (he says gritting teeth)
would be much appreciated.

--
Garry Wright
R-068 C-FOKM Amphib
403 931 1573
wrightdg@davincibb.net

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Posted: **Sat Feb 18, 2012 2:33 pm**

Dextron III. non-mil spec. I think the movement of the ring in the slot
is probably a red-herring but not absolutely certain. Thanks for the try
Bob. According to my supplier, he believes most O-rings contain buna
material with exceptions like special teflon ones etc.

On Fri, 2005-16-12 at 12:07 -0500, Bob Patterson wrote:

Hi Garry !

May be irrelevant, but what are you using for brake fluid ??
The Murphy factory always used ATF - NOT brake fluid. The Automatic
Transmission Fluid - from Canadian Tire, of course ! ;-) - works
great, and doesn't make such a mess of paint and hands.

Just wondered, as some O-rings may swell or leak if they get
the wrong fluid ....

Maybe you could add an elastic to the groove to keep the ring
more in place ???? :-) :-) ;-^)

.....bobp

-------------------------------orig.-------------------------
On Friday 16 December 2005 11:23 am, wrightdg wrote:
I have the brass colored Matco wheels and brakes on FOKM and am having
trouble with a leak in the left brake. I have had it apart about 4
times, replaced the O-ring, pads and generally cleaned it up and it
still seems to leak from the piston area.

The O-ring I replaced in kind but it does have lateral movement along
the axis of the piston in the O-ring slot. ie: the O-ring would have to
be elliptical in x-section or else another element would be needed in
the slot to stop axial movement of the ring. The piston fits nicely with
the O-ring so the axial movement must be intentional.

The caliper housing is a PH-1 and the drawing from this website does not
show any extra bits in the O-ring slot.

http://matco.elixirlabs.com/users/matco ... akes4a.jpg

Any advice on this before I take it apart again (he says gritting teeth)
would be much appreciated.

--
Garry Wright
R-068 C-FOKM Amphib
403 931 1573
wrightdg@davincibb.net

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Posted: **Sat Feb 18, 2012 2:33 pm**

Try the next size up O ring in width not circumferance if it appears that
there is movement. Lubricate the piston really good before assembly maybe
with silicon grease.

Steve W.

a >From: wrightdg <wrightdg@davincibb.net>

Reply-To: <rebel-builders@dcsol.com>
To: rebel builders <rebel-builders@dcsol.com>
Subject: Re: brake repairs on rebel
Date: Fri, 16 Dec 2005 11:36:11 -0700

Dextron III. non-mil spec. I think the movement of the ring in the slot
is probably a red-herring but not absolutely certain. Thanks for the try
Bob. According to my supplier, he believes most O-rings contain buna
material with exceptions like special teflon ones etc.

On Fri, 2005-16-12 at 12:07 -0500, Bob Patterson wrote:
Hi Garry !

May be irrelevant, but what are you using for brake fluid ??
The Murphy factory always used ATF - NOT brake fluid. The Automatic
Transmission Fluid - from Canadian Tire, of course ! ;-) - works
great, and doesn't make such a mess of paint and hands.

Just wondered, as some O-rings may swell or leak if they get
the wrong fluid ....

Maybe you could add an elastic to the groove to keep the ring
more in place ???? :-) :-) ;-^)

.....bobp

-------------------------------orig.-------------------------
On Friday 16 December 2005 11:23 am, wrightdg wrote:
I have the brass colored Matco wheels and brakes on FOKM and am having
trouble with a leak in the left brake. I have had it apart about 4
times, replaced the O-ring, pads and generally cleaned it up and it
still seems to leak from the piston area.

The O-ring I replaced in kind but it does have lateral movement along
the axis of the piston in the O-ring slot. ie: the O-ring would have
to
be elliptical in x-section or else another element would be needed in
the slot to stop axial movement of the ring. The piston fits nicely
with
the O-ring so the axial movement must be intentional.

The caliper housing is a PH-1 and the drawing from this website does
not
show any extra bits in the O-ring slot.

http://matco.elixirlabs.com/users/matco ... akes4a.jpg

Any advice on this before I take it apart again (he says gritting
teeth)
would be much appreciated.

--
Garry Wright
R-068 C-FOKM Amphib
403 931 1573
wrightdg@davincibb.net

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List administrator: mike.davis@dcsol.com
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Posted: **Sat Feb 18, 2012 2:33 pm**

Buna should be fine for this application. I'd look carefully for a
scratched piston or cylinder slot and for debris or burrs.

Also does anybody recall the details on the brake cylinder piston
advisory a few years ago?? It was not from MAM and I don't know if it
applied to anything that MAM uses. The drift of it was that some pistons
were extending too far causing leaks and loss of braking. It might have
been Clevelands that were shipped with the wrong pistons but I don't
remember...

Ken

wrightdg wrote:

Dextron III. non-mil spec. I think the movement of the ring in the slot
is probably a red-herring but not absolutely certain. Thanks for the try
Bob. According to my supplier, he believes most O-rings contain buna
material with exceptions like special teflon ones etc.

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Posted: **Sat Feb 18, 2012 2:33 pm**

Thanks Steve,Ken & Bob. I will be trying most of these things at the
earliest opportunity. Garry

On Fri, 2005-16-12 at 15:57 -0500, Ken wrote:

Buna should be fine for this application. I'd look carefully for a
scratched piston or cylinder slot and for debris or burrs.

Also does anybody recall the details on the brake cylinder piston
advisory a few years ago?? It was not from MAM and I don't know if it
applied to anything that MAM uses. The drift of it was that some pistons
were extending too far causing leaks and loss of braking. It might have
been Clevelands that were shipped with the wrong pistons but I don't
remember...

Ken

wrightdg wrote:

Dextron III. non-mil spec. I think the movement of the ring in the slot
is probably a red-herring but not absolutely certain. Thanks for the try
Bob. According to my supplier, he believes most O-rings contain buna
material with exceptions like special teflon ones etc.

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List administrator: mike.davis@dcsol.com
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