Home » Public Forums » GMCnet » [GMCnet] Brake bleeding—new MC and rear disks
| [GMCnet] Brake bleeding—new MC and rear disks [message #347703] |
Wed, 11 September 2019 20:05  |
Richard Denney
Messages: 920
Registered: April 2010
Karma: 9
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Senior Member |
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For those of you who have replaced master cylinders while installing rear
disks (including modifying the combo valve to remove the delay piston),
what bleeding method worked?
I ran maybe two quarts through the system using JimH’s pressure bleeder,
and at least another quart using a helper (who is a certified aircraft
mechanic) pumping the pedal. I’m still not really sure I have the air out
of it. I’m letting it settle now—did the bleeding on Monday and am going
back tomorrow—but if the pedal still feels mushy (especially with the
engine running), I’m out of ideas.
Rick “wishing he had a tighter-fitting 10mm wrench for those bleeders”
Denney
--
'73 X-Glacier 230 "Jaws"
Northern Virginia
Offlist email: rick at rickdenney dot com
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| Re: [GMCnet] Brake bleeding—new MC and rear disks [message #347707 is a reply to message #347703] |
Wed, 11 September 2019 20:19  |
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ljdavick
Messages: 3548
Registered: March 2007
Location: Fremont, CA
Karma: -3
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Senior Member |
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Denny,
I like my Harbor Freight vacuum bleeder. I haven’t used it on the coach, though. It worked well for our Sequoia and the Vanagon.
https://www.harborfreight.com/brake-fluid-bleeder-92924.html
Larry Davick
A Mystery Machine
Fremont
> On Sep 11, 2019, at 6:05 PM, Richard Denney via Gmclist wrote:
>
> For those of you who have replaced master cylinders while installing rear
> disks (including modifying the combo valve to remove the delay piston),
> what bleeding method worked?
>
> I ran maybe two quarts through the system using JimH’s pressure bleeder,
> and at least another quart using a helper (who is a certified aircraft
> mechanic) pumping the pedal. I’m still not really sure I have the air out
> of it. I’m letting it settle now—did the bleeding on Monday and am going
> back tomorrow—but if the pedal still feels mushy (especially with the
> engine running), I’m out of ideas.
>
> Rick “wishing he had a tighter-fitting 10mm wrench for those bleeders”
> Denney
> --
> '73 X-Glacier 230 "Jaws"
> Northern Virginia
> Offlist email: rick at rickdenney dot com
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
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Larry Davick
A Mystery Machine
1976(ish) Palm Beach
Fremont, Ca
Howell EFI + EBL + Electronic Dizzy
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| Re: [GMCnet] Brake bleeding--new MC and rear disks [message #347710 is a reply to message #347703] |
Wed, 11 September 2019 20:40 |
Carl S.
Messages: 4186
Registered: January 2009
Location: Tucson, AZ.
Karma: 13
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Senior Member |
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Rick,
When I installed the Chuck Aulgur Reaction Arm system, along with the disc brakes, I had to unbolt the top of the rear calipers and tilt them so the bleeder screws were at the very top (highest point) so there was not an air pocket trapped above the bleeder screw. This info came from Jim K after I was having trouble getting all the air out.
That said, the P-30 master cylinder and disc brake system has a completely different feel than the stock system had. I got used to it.
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles, Solar battery charging. GMCSJ and GMCMI member
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| Re: [GMCnet] Brake bleeding--new MC and rear disks [message #347712 is a reply to message #347710] |
Wed, 11 September 2019 20:52 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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If you have the P-30 mc, and you were not careful about the length of the
operating plunger, you will have symptoms of low pedal "feel". Especially
until the brake pads wear in to the new rotors. Careful break-in is
necessary, starting with light pedal pressure and gradually increasing it
as the pads wear in. You will NOT have the same pedal feel even when broken
in.
Jim Hupy
Salem, Or
On Wed, Sep 11, 2019, 6:41 PM Carl Stouffer via Gmclist <
gmclist@list.gmcnet.org> wrote:
> Rick,
>
> When I installed the Chuck Aulgur Reaction Arm system, along with the disc
> brakes, I had to unbolt the top of the rear calipers and tilt them so the
> bleeder screws were at the very top (highest point) so there was not an
> air pocket trapped above the bleeder screw. This info came from Jim K
> after I
> was having trouble getting all the air out.
>
> That said, the P-30 master cylinder and disc brake system has a completely
> different feel than the stock system had. I got used to it.
>
> --
> Carl Stouffer
> '75 ex Palm Beach
> Tucson, AZ.
> Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive,
> Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American
> Eagles,
> Solar battery charging. GMCSJ and GMCMI member
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
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| Re: [GMCnet] Brake bleeding--new MC and rear disks [message #347713 is a reply to message #347709] |
Wed, 11 September 2019 21:25 |
Richard Denney
Messages: 920
Registered: April 2010
Karma: 9
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Senior Member |
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Not a dumb question. I did not, but I figured with the power bleeder, it
would bleed the MC while installed as easily as on the bench.
The MC has no bleeders in any case, and will just empty out through the
ports if the piston is depressed. I can unhook the brake likes and pump
fluid through it, and then bleed the brakes again, if that really has hope
of accomplishing anything.
Rick “reluctant to open it up again” Denney
On Wed, Sep 11, 2019 at 9:35 PM Sean Kidd via Gmclist <
gmclist@list.gmcnet.org> wrote:
> Don't want to ask dumb questions, but did you bench bleed the MC? And the
> rear calipers are clocked correctly so the bleed screw on top?
> --
> Sean and Stephanie
> 73 Ex-CanyonLands 26' #317 "Oliver"
> Hubler 1-Ton, Quad-Bags, Rear Disc, Reaction Arms, P.Huber TBs, 3.70:1 LSD
> Honda 6500 inverter gen.
>
> Colonial Travelers
>
> _______________________________________________
> GMCnet mailing list
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>
--
'73 X-Glacier 230 "Jaws"
Northern Virginia
Offlist email: rick at rickdenney dot com
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| Re: [GMCnet] Brake bleeding--new MC and rear disks [message #347714 is a reply to message #347710] |
Wed, 11 September 2019 21:28 |
Richard Denney
Messages: 920
Registered: April 2010
Karma: 9
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Senior Member |
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Thanks—I’ll have that in the hopper. Not hard to do right now, but harder
after I get it back on its wheels.
Rick “also holding the bleeder bottle high to keep draining fluid from
pulling air around the loosened bleeder threads” Denney
On Wed, Sep 11, 2019 at 9:41 PM Carl Stouffer via Gmclist <
gmclist@list.gmcnet.org> wrote:
> Rick,
>
> When I installed the Chuck Aulgur Reaction Arm system, along with the disc
> brakes, I had to unbolt the top of the rear calipers and tilt them so the
> bleeder screws were at the very top (highest point) so there was not an
> air pocket trapped above the bleeder screw. This info came from Jim K
> after I
> was having trouble getting all the air out.
>
> That said, the P-30 master cylinder and disc brake system has a completely
> different feel than the stock system had. I got used to it.
>
> --
> Carl Stouffer
> '75 ex Palm Beach
> Tucson, AZ.
> Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive,
> Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American
> Eagles,
> Solar battery charging. GMCSJ and GMCMI member
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
'73 X-Glacier 230 "Jaws"
Northern Virginia
Offlist email: rick at rickdenney dot com
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| Re: [GMCnet] Brake bleeding--new MC and rear disks [message #347715 is a reply to message #347712] |
Wed, 11 September 2019 21:34 |
Richard Denney
Messages: 920
Registered: April 2010
Karma: 9
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Senior Member |
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Jim,
I’m using the stock master cylinder, recognizing that I must check the
fluid level routinely, since the rear reservoirs won’t hold enough to
accommodate full pad wear. But I wanted the smaller piston for higher
pressure. I have the rear calipers with the parking brake adjusted snugly,
so there is no gap other than what is left by runout.
The new MC has the same pushrod depth as the old one that I’ve been using
for 16 years. That doesn’t mean it’s right, of course.
Rick “who did not measure pushrod clearance” Denney
On Wed, Sep 11, 2019 at 9:50 PM James Hupy via Gmclist <
gmclist@list.gmcnet.org> wrote:
> If you have the P-30 mc, and you were not careful about the length of the
> operating plunger, you will have symptoms of low pedal "feel". Especially
> until the brake pads wear in to the new rotors. Careful break-in is
> necessary, starting with light pedal pressure and gradually increasing it
> as the pads wear in. You will NOT have the same pedal feel even when broken
> in.
> Jim Hupy
> Salem, Or
>
> On Wed, Sep 11, 2019, 6:41 PM Carl Stouffer via Gmclist gmclist@list.gmcnet.org> wrote:
>
>> Rick,
>>
>> When I installed the Chuck Aulgur Reaction Arm system, along with the
> disc
>> brakes, I had to unbolt the top of the rear calipers and tilt them so the
>> bleeder screws were at the very top (highest point) so there was not an
>> air pocket trapped above the bleeder screw. This info came from Jim K
>> after I
>> was having trouble getting all the air out.
>>
>> That said, the P-30 master cylinder and disc brake system has a
> completely
>> different feel than the stock system had. I got used to it.
>>
>> --
>> Carl Stouffer
>> '75 ex Palm Beach
>> Tucson, AZ.
>> Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive,
>> Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American
>> Eagles,
>> Solar battery charging. GMCSJ and GMCMI member
>>
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
'73 X-Glacier 230 "Jaws"
Northern Virginia
Offlist email: rick at rickdenney dot com
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| Re: [GMCnet] Brake bleeding--new MC and rear disks [message #347718 is a reply to message #347715] |
Wed, 11 September 2019 21:52 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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That eliminates a huge source of soft pedal. If your system doesn't improve
with break-in, then, you probably DO have air trapped somewhere. I have had
a couple coaches that I fought for a while. Both had P-30 mc.
Jim Hupy
Salem, Oregon
On Wed, Sep 11, 2019, 7:35 PM Richard Denney via Gmclist <
gmclist@list.gmcnet.org> wrote:
> Jim,
>
> I’m using the stock master cylinder, recognizing that I must check the
> fluid level routinely, since the rear reservoirs won’t hold enough to
> accommodate full pad wear. But I wanted the smaller piston for higher
> pressure. I have the rear calipers with the parking brake adjusted snugly,
> so there is no gap other than what is left by runout.
>
> The new MC has the same pushrod depth as the old one that I’ve been using
> for 16 years. That doesn’t mean it’s right, of course.
>
> Rick “who did not measure pushrod clearance” Denney
>
> On Wed, Sep 11, 2019 at 9:50 PM James Hupy via Gmclist gmclist@list.gmcnet.org> wrote:
>
>> If you have the P-30 mc, and you were not careful about the length of the
>> operating plunger, you will have symptoms of low pedal "feel". Especially
>> until the brake pads wear in to the new rotors. Careful break-in is
>> necessary, starting with light pedal pressure and gradually increasing it
>> as the pads wear in. You will NOT have the same pedal feel even when
> broken
>> in.
>> Jim Hupy
>> Salem, Or
>>
>> On Wed, Sep 11, 2019, 6:41 PM Carl Stouffer via Gmclist > gmclist@list.gmcnet.org> wrote:
>>
>>> Rick,
>>>
>>> When I installed the Chuck Aulgur Reaction Arm system, along with the
>> disc
>>> brakes, I had to unbolt the top of the rear calipers and tilt them so
> the
>>> bleeder screws were at the very top (highest point) so there was not an
>>> air pocket trapped above the bleeder screw. This info came from Jim K
>>> after I
>>> was having trouble getting all the air out.
>>>
>>> That said, the P-30 master cylinder and disc brake system has a
>> completely
>>> different feel than the stock system had. I got used to it.
>>>
>>> --
>>> Carl Stouffer
>>> '75 ex Palm Beach
>>> Tucson, AZ.
>>> Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final
> drive,
>>> Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American
>>> Eagles,
>>> Solar battery charging. GMCSJ and GMCMI member
>>>
>>> _______________________________________________
>>> GMCnet mailing list
>>> Unsubscribe or Change List Options:
>>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>>
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>
> --
> '73 X-Glacier 230 "Jaws"
> Northern Virginia
> Offlist email: rick at rickdenney dot com
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
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| Re: [GMCnet] Brake bleeding--new MC and rear disks [message #347722 is a reply to message #347718] |
Wed, 11 September 2019 22:40 |
Richard Denney
Messages: 920
Registered: April 2010
Karma: 9
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Senior Member |
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Jim, do you think I messed myself up by not bench-bleeding the MC?
Rick “who’ll do it if necessary” Denney
On Wed, Sep 11, 2019 at 10:50 PM James Hupy via Gmclist <
gmclist@list.gmcnet.org> wrote:
> That eliminates a huge source of soft pedal. If your system doesn't improve
> with break-in, then, you probably DO have air trapped somewhere. I have had
> a couple coaches that I fought for a while. Both had P-30 mc.
> Jim Hupy
> Salem, Oregon
>
> On Wed, Sep 11, 2019, 7:35 PM Richard Denney via Gmclist gmclist@list.gmcnet.org> wrote:
>
>> Jim,
>>
>> I’m using the stock master cylinder, recognizing that I must check the
>> fluid level routinely, since the rear reservoirs won’t hold enough to
>> accommodate full pad wear. But I wanted the smaller piston for higher
>> pressure. I have the rear calipers with the parking brake adjusted
> snugly,
>> so there is no gap other than what is left by runout.
>>
>> The new MC has the same pushrod depth as the old one that I’ve been using
>> for 16 years. That doesn’t mean it’s right, of course.
>>
>> Rick “who did not measure pushrod clearance” Denney
>>
>> On Wed, Sep 11, 2019 at 9:50 PM James Hupy via Gmclist > gmclist@list.gmcnet.org> wrote:
>>
>>> If you have the P-30 mc, and you were not careful about the length of
> the
>>> operating plunger, you will have symptoms of low pedal "feel".
> Especially
>>> until the brake pads wear in to the new rotors. Careful break-in is
>>> necessary, starting with light pedal pressure and gradually increasing
> it
>>> as the pads wear in. You will NOT have the same pedal feel even when
>> broken
>>> in.
>>> Jim Hupy
>>> Salem, Or
>>>
>>> On Wed, Sep 11, 2019, 6:41 PM Carl Stouffer via Gmclist >> gmclist@list.gmcnet.org> wrote:
>>>
>>>> Rick,
>>>>
>>>> When I installed the Chuck Aulgur Reaction Arm system, along with the
>>> disc
>>>> brakes, I had to unbolt the top of the rear calipers and tilt them so
>> the
>>>> bleeder screws were at the very top (highest point) so there was not
> an
>>>> air pocket trapped above the bleeder screw. This info came from Jim
> K
>>>> after I
>>>> was having trouble getting all the air out.
>>>>
>>>> That said, the P-30 master cylinder and disc brake system has a
>>> completely
>>>> different feel than the stock system had. I got used to it.
>>>>
>>>> --
>>>> Carl Stouffer
>>>> '75 ex Palm Beach
>>>> Tucson, AZ.
>>>> Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final
>> drive,
>>>> Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American
>>>> Eagles,
>>>> Solar battery charging. GMCSJ and GMCMI member
>>>>
>>>> _______________________________________________
>>>> GMCnet mailing list
>>>> Unsubscribe or Change List Options:
>>>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>>>
>>> _______________________________________________
>>> GMCnet mailing list
>>> Unsubscribe or Change List Options:
>>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>>
>> --
>> '73 X-Glacier 230 "Jaws"
>> Northern Virginia
>> Offlist email: rick at rickdenney dot com
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
'73 X-Glacier 230 "Jaws"
Northern Virginia
Offlist email: rick at rickdenney dot com
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| Re: [GMCnet] Brake bleeding--new MC and rear disks [message #347723 is a reply to message #347722] |
Wed, 11 September 2019 23:31 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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Yes, the best method is to bench bleed the m.c. But, you can perform the
process on the coach just as easily. One trick I use is to fill the
reservoirs just using the bleeder pump. An assistant is handy for this.
Take the plate off the top of the m.c. and observe what happens when you
SLOWLY depress the brake pedal. If you see any air bubbles, it is possible
you might have a defective new master cylinder. You should only see an
eruption of fluid above the ports, no air bubbles at all.
Jim Hupy
Salem, Or
On Wed, Sep 11, 2019, 8:41 PM Richard Denney via Gmclist <
gmclist@list.gmcnet.org> wrote:
> Jim, do you think I messed myself up by not bench-bleeding the MC?
>
> Rick “who’ll do it if necessary” Denney
>
> On Wed, Sep 11, 2019 at 10:50 PM James Hupy via Gmclist gmclist@list.gmcnet.org> wrote:
>
>> That eliminates a huge source of soft pedal. If your system doesn't
> improve
>> with break-in, then, you probably DO have air trapped somewhere. I have
> had
>> a couple coaches that I fought for a while. Both had P-30 mc.
>> Jim Hupy
>> Salem, Oregon
>>
>> On Wed, Sep 11, 2019, 7:35 PM Richard Denney via Gmclist > gmclist@list.gmcnet.org> wrote:
>>
>>> Jim,
>>>
>>> I’m using the stock master cylinder, recognizing that I must check the
>>> fluid level routinely, since the rear reservoirs won’t hold enough to
>>> accommodate full pad wear. But I wanted the smaller piston for higher
>>> pressure. I have the rear calipers with the parking brake adjusted
>> snugly,
>>> so there is no gap other than what is left by runout.
>>>
>>> The new MC has the same pushrod depth as the old one that I’ve been
> using
>>> for 16 years. That doesn’t mean it’s right, of course.
>>>
>>> Rick “who did not measure pushrod clearance” Denney
>>>
>>> On Wed, Sep 11, 2019 at 9:50 PM James Hupy via Gmclist >> gmclist@list.gmcnet.org> wrote:
>>>
>>>> If you have the P-30 mc, and you were not careful about the length of
>> the
>>>> operating plunger, you will have symptoms of low pedal "feel".
>> Especially
>>>> until the brake pads wear in to the new rotors. Careful break-in is
>>>> necessary, starting with light pedal pressure and gradually
> increasing
>> it
>>>> as the pads wear in. You will NOT have the same pedal feel even when
>>> broken
>>>> in.
>>>> Jim Hupy
>>>> Salem, Or
>>>>
>>>> On Wed, Sep 11, 2019, 6:41 PM Carl Stouffer via Gmclist >>> gmclist@list.gmcnet.org> wrote:
>>>>
>>>> > Rick,
>>>> >
>>>> > When I installed the Chuck Aulgur Reaction Arm system, along with
> the
>>>> disc
>>>> > brakes, I had to unbolt the top of the rear calipers and tilt them
> so
>>> the
>>>> > bleeder screws were at the very top (highest point) so there was
> not
>> an
>>>> > air pocket trapped above the bleeder screw. This info came from
> Jim
>> K
>>>> > after I
>>>> > was having trouble getting all the air out.
>>>> >
>>>> > That said, the P-30 master cylinder and disc brake system has a
>>>> completely
>>>> > different feel than the stock system had. I got used to it.
>>>> >
>>>> > --
>>>> > Carl Stouffer
>>>> > '75 ex Palm Beach
>>>> > Tucson, AZ.
>>>> > Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final
>>> drive,
>>>> > Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear
> American
>>>> > Eagles,
>>>> > Solar battery charging. GMCSJ and GMCMI member
>>>> >
>>>> > _______________________________________________
>>>> > GMCnet mailing list
>>>> > Unsubscribe or Change List Options:
>>>> > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>>> >
>>>> _______________________________________________
>>>> GMCnet mailing list
>>>> Unsubscribe or Change List Options:
>>>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>>>
>>> --
>>> '73 X-Glacier 230 "Jaws"
>>> Northern Virginia
>>> Offlist email: rick at rickdenney dot com
>>> _______________________________________________
>>> GMCnet mailing list
>>> Unsubscribe or Change List Options:
>>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>>
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>
> --
> '73 X-Glacier 230 "Jaws"
> Northern Virginia
> Offlist email: rick at rickdenney dot com
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
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| Re: [GMCnet] Brake bleeding--new MC and rear disks [message #347724 is a reply to message #347723] |
Thu, 12 September 2019 00:03 |
Hal StClair
Messages: 971
Registered: March 2013
Location: Rio Rancho NM
Karma: -12
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Senior Member |
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I'd bleed the M/C for sure. Air seems to get trapped in those buggers even using Jim's bleeder. Some of the rear discs have an awful lot of run out or backing plate flex which causes knock back of the caliper pistons and will give lousy pedal feel also. Sometimes a 2 lb residual valve works well to make everything tight again. I know it's a crutch, but it does seem to work. Good luck, Hal
"I enjoy talking to you. Your mind appeals to me. It resembles my own mind, except you happen to be insane."
1977 Royale 101348,
1977 Royale 101586, Diesel powered,
1974 Eagle Bus 45',w/slideout,
Rio Rancho, NM
[Updated on: Thu, 12 September 2019 23:55] Report message to a moderator |
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| Re: [GMCnet] Brake bleeding--new MC and rear disks [message #347725 is a reply to message #347724] |
Thu, 12 September 2019 02:16 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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Hal, I have noticed what you are talking about. More so on one reaction arm
kit. I mentioned that to the builder. Gotta watch that rotor run out, and
keep it to the minimum possible amount. Less than .010 for sure.
Jim Hupy
On Wed, Sep 11, 2019, 10:04 PM Hal StClair via Gmclist <
gmclist@list.gmcnet.org> wrote:
> I'd bleed the M/C for sure. Air seems to get trapped in those buggers even
> using Jim's bleeder. Some of the rear discs have an awful lot of run out or
> backing plate flex which causes knock back of the caliper pistons and will
> give lousy pedal feel also. Sometimes a 2 lb residual valve works well to
> make everything tight again. I know it's a crutch, but it does seem to
> work. Good luck, Hal
> --
> 1977 Royale 101348,
>
> 1977 Royale 101586, Diesel powered,
>
> 1975 Eleganza II, 101230,
>
> 1974 Eagle Bus 45',w/slideout,
>
> Rio Rancho, NM
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
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| Re: [GMCnet] Brake bleeding--new MC and rear disks [message #347728 is a reply to message #347725] |
Thu, 12 September 2019 05:51 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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If your MC did not come with it, get the very cheap plastic bench bleed kit from AZ, or whatever parts store you like. Usually less the $5.00. Mount the MC perfectly level in a vice, Install the correct fitting from the kit and fill half way. Start pumping slowly. Pause after each stroke. Watch both the exit hoses and the intake port at the bottom of the reservoir for air bubbles. When there are not more bubbles tap it lightly with a hammer to loosen any trapped bubbles and pump a few more times.
Then tilt the MC slightly up on one end and use a couple of quarters or nickels as wedges and tighten in the vice again. Start slow pumping again. When there are no bubbles, remount it tilted the other way and do it a a third time. You are done when there there are no more bubbles.
The problem doing it on coach is the MC is not mounted level and you almost always trap air because of that.
After mounting and reattaching the lines, initially pressure or vacuum bleed so you do not to suck air back into the MC when pumping the pedal. You want any air in the system from the line disconnection to travel down the line and out the bleeder.
Clocking the wheel cylinder is extremely important. If they are not clocked correctly you will never get all of the air out of the system. Since you are installing them in a non standard configuration you might have to remove one of the mounting bolts to rotate the caliper into a position with the bleeder at the exact top to bleed all of the air out.
Ken B.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Brake bleeding--new MC and rear disks [message #347749 is a reply to message #347724] |
Thu, 12 September 2019 13:53 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Senior Member |
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Rick,
Do you have an electric vacuum pump? Or have a used appliance dealer handy
from whom you might get a refrigerator compressor -- from which to make a
vacuum pump?
In tough cases, I've put a cap like Jim Hupy's on the MC and kept a vacuum
on it for several hours. That WILL get all the air out of the system,
without the trouble of going back to bench bleeding the MC.
One caution: If you're running a MC with cup seals, the vacuum MAY pull
air past those and make the situation worse. I've generally used it with
P-30 MC's which have O-ring seals. Not the case for you, but with drums,
that's a bigger problem because of the cups in the wheel cylinders.
Ken H.
On Thu, Sep 12, 2019 at 1:04 AM Hal StClair via Gmclist <
gmclist@list.gmcnet.org> wrote:
> I'd bleed the M/C for sure. Air seems to get trapped in those buggers even
> using Jim's bleeder. Some of the rear discs have an awful lot of run out or
> backing plate flex which causes knock back of the caliper pistons and will
> give lousy pedal feel also. Sometimes a 2 lb residual valve works well to
> make everything tight again. I know it's a crutch, but it does seem to
> work. Good luck, Hal
> --
> 1977 Royale 101348,
>
> 1977 Royale 101586, Diesel powered,
>
> 1975 Eleganza II, 101230,
>
> 1974 Eagle Bus 45',w/slideout,
>
> Rio Rancho, NM
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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| Re: [GMCnet] Brake bleeding--new MC and rear disks [message #347753 is a reply to message #347749] |
Thu, 12 September 2019 18:27 |
Richard Denney
Messages: 920
Registered: April 2010
Karma: 9
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Senior Member |
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So, I took the day off today and gave it a fresh start. When I arrived, the
pedal was low but seemed hard enough (engine not running).
I had already decided to bite the bullet and pull the master cylinder.
Which I did. I bench-bled it using the kit KenB mentioned which I found at
Autozone. It has plastic fittings with hose barbs that screw into the
output fittings. The hoses fit on those, and clip to the septum between the
two reservoirs, with the hoses dipped in the reservoirs. This recycles the
brake fluid and there should be no bubbles after clearing the hoses. I
pumped the master cylinder at the several angles, and tapped on it to
dislodge bubbles, and got all the air out. I put the cap on and clamped the
hoses shut to seal it up.
Then, I took a good look at the mounting. The MC was in front of the
bracket, which was between the MC and the booster. I recall a presentation
from Lenzi suggesting that was wrong for early coaches. I assumed my
pushrod had been modified, but now I think I just accommodated myself to
the greater pedal travel. I test-fit the MC without the bracket, and I am
sure the pushrod did not press the piston when I snuggled up the nuts
(fingers were enough to fully seat the MC).
So, I then noticed that the bracket had been “adjusted” to fit behind the
MC, and I unadjusted it. I know why some past mechanic did it—getting those
upper bolts back in the bracket is...unpleasant. There is nothing to pry
against and it was all a bit too tight. But I got it done.
The flange ears on the MC were 11/16” thick and the old MC was the more
correct 9/16”. Lenzi would have adjusted that in a mill; I used an air
grinder. It worked.
Then, I used JimH’s bleeder and bled 1.5 quarts through the system. No
bubbles.
Now, the pedal is high and hard, and feels right. With vacuum boost, it’s
hard to tell anything, but that’s always been true for me. I can push the
pedal way down, but I can’t bottom it out. After shutting down and pumping
the vacuum out of the booster, the pedal is high and hard again.
Saturday, I’ll get it off the stands and drive it.
Rick “still watching one bleeder that wants to seep just a bit” Denney
On Thu, Sep 12, 2019 at 2:55 PM Ken Henderson via Gmclist <
gmclist@list.gmcnet.org> wrote:
> Rick,
>
> Do you have an electric vacuum pump? Or have a used appliance dealer handy
> from whom you might get a refrigerator compressor -- from which to make a
> vacuum pump?
>
> In tough cases, I've put a cap like Jim Hupy's on the MC and kept a vacuum
> on it for several hours. That WILL get all the air out of the system,
> without the trouble of going back to bench bleeding the MC.
>
> One caution: If you're running a MC with cup seals, the vacuum MAY pull
> air past those and make the situation worse. I've generally used it with
> P-30 MC's which have O-ring seals. Not the case for you, but with drums,
> that's a bigger problem because of the cups in the wheel cylinders.
>
> Ken H.
>
--
'73 X-Glacier 230 "Jaws"
Northern Virginia
Offlist email: rick at rickdenney dot com
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