Home » Public Forums » GMCnet » [GMCnet] Brake bleeding—new MC and rear disks
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| Re: [GMCnet] Brake bleeding--new MC and rear disks [message #347777 is a reply to message #347775] |
Fri, 13 September 2019 13:16   |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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Quality of the offshore mfd parts leaves a lot to be desired, particularly
on brake calipers, and their threaded parts as well. You might try
replacing the bleeder screws, but be careful to match up the threads with
what you have, and the wrench size too. Centric I know is made in China. I
long for the days of Wagner Lockheed and Bendix. Alas, they exist only in
memories today.
Jim Hupy
Salem, Oregon
On Fri, Sep 13, 2019, 10:24 AM Richard Denney via Gmclist <
gmclist@list.gmcnet.org> wrote:
> Both me and the Redhead’s uncle hope so.
>
> Anybody have experience with seeping bleeders? I’m thinking the machining
> of the seat has to be just about perfect for the bleeder screw to seat
> properly and provide a seal. So, replacing the bleeder screw is unlikely to
> fix a leak (though I’m going to try it anyway). Seems to be a common
> problem that a bleeder with a softer nose would help address, but those
> don’t seem to be made. I had problems with all four bleeders, and they all
> required more tightening than I expected. But one is still persistently
> seeping—not enough to drip, so I may have to live with it for a while.
>
> Rick “who never used to have problems with bleeders, unless they were
> corroded in place” Denney
>
> On Fri, Sep 13, 2019 at 3:07 AM Ken Burton via Gmclist gmclist@list.gmcnet.org> wrote:
>
>> It sounds like you are close to being finished....Great.
>>
>> Ken B.
>> --
>> Ken Burton - N9KB
>> 76 Palm Beach
>> Hebron, Indiana
>>
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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 #347780 is a reply to message #347703] |
Fri, 13 September 2019 14:07 |
TR 1
Messages: 348
Registered: August 2015
Location: DFW
Karma: -7
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Senior Member |
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I assume you tried checking the bleeder and the seats for debris or any sort of defect that would allow fluid to escape....
If you have and that's not the issue, another option is they do make these conical copper washer like things that actually fit in the tapper on the brake fitting, though I've never actually used them on a bleeder, I have used them on brake lines, and I'd imagine they would work the same way on a bleeder....
Backstory on the conical washers is a while back I'd bought some stainless braided brake lines from Goodridge, and I had leak issues... Called their customer service and they went and sent me a set of these washers and they solved the issue....
They look similar to this:
http://www.aektechnology.com/airdrome/AEK_Conical_1114.pdf
Mark S. '73 Painted Desert,
Manny 1 Ton Front End,
Howell Injection,
Leigh Harrison 4bag and Rear Brakes,
Fort Worth, TX
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| Re: [GMCnet] Brake bleeding--new MC and rear disks [message #347788 is a reply to message #347775] |
Fri, 13 September 2019 20:16 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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I have used teflon tape on the threaded part of the bleeders for years. This accomplishes 2 things. The do not seep air when vacuum bleeding and 5 or 10 years from now when you want to bleed them again they are not rusted in place. I have also used anti-seize on the threads.
I consider it a requirement to put the rubber caps on the bleeder screws when I am finished bleeding.
If you do not have them you can buy just the caps on ebay.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Brake bleeding--new MC and rear disks [message #347847 is a reply to message #347813] |
Sat, 14 September 2019 19:41 |
Richard Denney
Messages: 920
Registered: April 2010
Karma: 9
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Senior Member |
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In the end, I replaced the bleeder screws in two calipers with new ones
from NAPA. I used Teflon tape on the threads to make them easier to loosen,
and so far no leaks.
I got it all buttoned up today and took the coach for a drive. The coach
tracks straight as an arrow, now that I have tight bogie bushings.
Everything seemed to work as it should.
The coach stops, and it does so reliably. Lots of pedal travel, though.
When I rent a car, which I do often given my travel schedule, the brakes on
those econoboxes are quite sudden and responsive. My Expedition brakes feel
sluggish on the way home from the airport. That coach braking feels more
sluggish than the Expedition by about the same amount. I’m sure hoping the
break-in of the new brakes will make them a bit grippier and more
responsive, and increase ultimate braking power. But it’s been on jack
stands for five weeks and I don’t trust my memory of how the brakes behaved
before. They did always require high pedal effort.
Rick “not knowing what to expect” Denney
On Sat, Sep 14, 2019 at 10:52 AM Matt Colie via Gmclist <
gmclist@list.gmcnet.org> wrote:
> Rick,
>
> Well, KenB already said what I think is a most important thing in brake
> maintenance.
>
> But, I will add that in my lengthy and lack-luster experience in passcar
> brakes, I have had two bad bleeder screws. Both had a visible mark on the
> sealing face. One I took back and the other I just took the screw out of
> the old cylinder.
>
> One time that I had a weeper like yours, I went and retightened it 3 or 4
> times with a 1/4 drive socket on a long extension and a T-handle so there
> was minimal side load. That seemed to get it.
>
> Good Luck
>
> Matt
> --
> Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
> Electronically Controlled Quiet Engine Cooling Fan
> OE Rear Drum Brakes with Applied Control Arms
> SE Michigan - Twixt A2 and Detroit
>
> _______________________________________________
> 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 #347855 is a reply to message #347851] |
Sun, 15 September 2019 10:58 |
Richard Denney
Messages: 920
Registered: April 2010
Karma: 9
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Senior Member |
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Which brings to mind my thinking this morning.
I’m noting a lot of pedal travel. The pads are in contact, and remain so
even with a test spin of the freshly mounted wheel. I did not explicitly
measure the runout, but it did not seem excessive. A little runout is
necessary to keep the pads from wearing and making constant heat in any
case.
That said, I’m using the stock MC, because its smaller piston results in
lower pedal effort. But it requires greater travel to move the same amount
of fluid. I’m wondering if the stock MC is a little too small, in terms of
volume moved over the pedal range, for six disk brakes. (I already know the
reservoirs are too small, and have to check fluid level routinely as the
pads wear.)
I may need the P30 to reduce pedal travel, and the sensitized booster to
restore the lower pedal effort lost to the larger piston, at least for
routine braking.
But I’m not going to think about this again until the current brakes are
fully broken in, so I can see where I am.
Rick “reversing the lines is just a matter of reservoir capacity, right?”
Denney
On Sun, Sep 15, 2019 at 8:48 AM Sean Kidd via Gmclist <
gmclist@list.gmcnet.org> wrote:
> Richard, one last note, I was instructed to reverse reservoirs when I did
> my rear discs. Original rear port on MC was to go on front Port on P-30 MC
> and vice versa.
>
--
'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 #347857 is a reply to message #347855] |
Sun, 15 September 2019 11:09 |
Richard Denney
Messages: 920
Registered: April 2010
Karma: 9
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Senior Member |
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By the way, I just ordered a set of Performance Friction pads for the rear
disks.
Rick “thinking it might help” Denney
On Sun, Sep 15, 2019 at 11:58 AM Richard Denney wrote:
> Which brings to mind my thinking this morning.
>
> I’m noting a lot of pedal travel. The pads are in contact, and remain so
> even with a test spin of the freshly mounted wheel. I did not explicitly
> measure the runout, but it did not seem excessive. A little runout is
> necessary to keep the pads from wearing and making constant heat in any
> case.
>
> That said, I’m using the stock MC, because its smaller piston results in
> lower pedal effort. But it requires greater travel to move the same amount
> of fluid. I’m wondering if the stock MC is a little too small, in terms of
> volume moved over the pedal range, for six disk brakes. (I already know the
> reservoirs are too small, and have to check fluid level routinely as the
> pads wear.)
>
> I may need the P30 to reduce pedal travel, and the sensitized booster to
> restore the lower pedal effort lost to the larger piston, at least for
> routine braking.
>
> But I’m not going to think about this again until the current brakes are
> fully broken in, so I can see where I am.
>
> Rick “reversing the lines is just a matter of reservoir capacity, right?”
> Denney
>
> On Sun, Sep 15, 2019 at 8:48 AM Sean Kidd via Gmclist gmclist@list.gmcnet.org> wrote:
>
>> Richard, one last note, I was instructed to reverse reservoirs when I did
>> my rear discs. Original rear port on MC was to go on front Port on P-30 MC
>> and vice versa.
>>
> --
> '73 X-Glacier 230 "Jaws"
> Northern Virginia
> Offlist email: rick at rickdenney dot com
>
--
'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 #347859 is a reply to message #347855] |
Sun, 15 September 2019 11:30 |
Emery Stora
Messages: 959
Registered: January 2011
Karma: 4
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Senior Member |
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Yes, the original master cylinder does not provide enough volume for six wheel disk brakes, especially if you have switched to 80m front calipers.
However, the P30 master cylinder give less pressure to the calipers. There are a lot of different P30 master cylinders. I would suggest the use of the GM 14009146 master cylinder which corresponds to an AC/Delco 174-834.
This also crosses to Wagner F103239, Bendix 11641, EIS E150063 and a CarQuest 20-2234. I don't have the NAPA cross.
This is a 34 mm piston bore (approx. 1-21/64”).
If you install a 34mm master cylinder then the brace will no longer fit on the front of the mounting lugs and you will have to bend it so that it fits between the booster and the master cylinder. That means that you will need a longer push rod.
You can grind your own or you can purchase an adjustable one. I recommend 0.015 inches (3.8mm) clearance between the end of the push rod and the piston.
You will encounter another problem with using the 34mm master cylinder. It will not seal properly against the rubber seal on the face of the booster and you will get a vacuum leak there. Dave Lenzi provided a small “collar” to me that would take up the gap and seal it properly.
When I recently removed the 4 rear calipers and disks and put on Dave Lenzi’s rear brake double piston caliper and larger disk on the mid axle I switched to the original master cylinder and even though I have no braking on the rear axle I have excellent braking now. Much better than with the 4 smaller rear disks. I will be installing Dave’s hydraulic parking brake on the caliper. It already has the mounts on it.
Emery Stora
77 Kingsley
Frederick, CO
> On Sep 15, 2019, at 9:58 AM, Richard Denney via Gmclist wrote:
>
> Which brings to mind my thinking this morning.
>
> I’m noting a lot of pedal travel. The pads are in contact, and remain so
> even with a test spin of the freshly mounted wheel. I did not explicitly
> measure the runout, but it did not seem excessive. A little runout is
> necessary to keep the pads from wearing and making constant heat in any
> case.
>
> That said, I’m using the stock MC, because its smaller piston results in
> lower pedal effort. But it requires greater travel to move the same amount
> of fluid. I’m wondering if the stock MC is a little too small, in terms of
> volume moved over the pedal range, for six disk brakes. (I already know the
> reservoirs are too small, and have to check fluid level routinely as the
> pads wear.)
>
> I may need the P30 to reduce pedal travel, and the sensitized booster to
> restore the lower pedal effort lost to the larger piston, at least for
> routine braking.
>
> But I’m not going to think about this again until the current brakes are
> fully broken in, so I can see where I am.
>
> Rick “reversing the lines is just a matter of reservoir capacity, right?”
> Denney
>
> On Sun, Sep 15, 2019 at 8:48 AM Sean Kidd via Gmclist gmclist@list.gmcnet.org> wrote:
>
>> Richard, one last note, I was instructed to reverse reservoirs when I did
>> my rear discs. Original rear port on MC was to go on front Port on P-30 MC
>> and vice versa.
>>
> --
> '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 #347877 is a reply to message #347775] |
Sun, 15 September 2019 17:05 |
Richard Denney
Messages: 920
Registered: April 2010
Karma: 9
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Senior Member |
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After all of yesterday’s second-guessing, I drove the coach home this
afternoon—about 40 miles. Within five miles, I’d forgotten about the
brakes. They just work, and I got used to the pedal travel and feel in no
time. I’ll check on maximum braking when they are really broken in.
Nothing got too hot (though the brakes were hot, which they have to be if
they are working). If I was having a bearing problem after installing the
reaction rods, the ends of the spindles would be hot; they weren’t.
But what had me smiling was that the coach drove more nimbly than my
Expedition. It tracked straight, never needed more than a single light hand
in the wheel, and didn’t change directions without permission. I am so glad
not to have wobbly shopping cart caster wheels any more.
Rick “the coach is now Redhead-driveable” Denney
On Fri, Sep 13, 2019 at 1:23 PM Richard Denney wrote:
> Both me and the Redhead’s uncle hope so.
>
--
'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 #347880 is a reply to message #347877] |
Sun, 15 September 2019 18:30 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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I installed a quadra-bag system along with a Chuck Algur reaction arm and 6
wheel disc brakes with Cadillac calipers on the rear/rear, for a customer
that lived in the West hills of Portland, Oregon. He drove his coach down
Canyon Blvd every Sunday morning.
After I installed the systems, he complained of a soft pedal and
excessive pedal travel. He brought the coach back to me to check out, as he
thought it should have a firmer pedal. So, I replaced the P-30 m.c. with a
stock one along with a sensitized booster, and installed 80 mm calipers on
stock rotors with sticky yellow ceramic front pads. I re-bled the system,
and returned the coach to him. He called after a couple of weeks, and said
that he thought the pedal should be firmer. I told him to drive it some
more to further break-in the discs and pads.
Some time passed, and no more calls from him. Then, one Sunday morning
while out for his weekly drive, a Honda ran into a center divider after
cutting in front of him without enough clearance, spun out, and came to
rest across both lanes directly in front of him. He said some expletives
and panic stopped his coach, knowing that if he were driving the stock
brakes that he was going to T-bone the Honda on the drivers door. Much to
his suprise, the coach stopped 10 feet short of contact. He pulled over and
called me and thanked me profusely for the disc conversion. So, I know
those systems work, but differently than what we are used to.
Jim Hupy
Salem, Oregon
On Sun, Sep 15, 2019, 3:06 PM Richard Denney via Gmclist <
gmclist@list.gmcnet.org> wrote:
> After all of yesterday’s second-guessing, I drove the coach home this
> afternoon—about 40 miles. Within five miles, I’d forgotten about the
> brakes. They just work, and I got used to the pedal travel and feel in no
> time. I’ll check on maximum braking when they are really broken in.
>
> Nothing got too hot (though the brakes were hot, which they have to be if
> they are working). If I was having a bearing problem after installing the
> reaction rods, the ends of the spindles would be hot; they weren’t.
>
> But what had me smiling was that the coach drove more nimbly than my
> Expedition. It tracked straight, never needed more than a single light hand
> in the wheel, and didn’t change directions without permission. I am so glad
> not to have wobbly shopping cart caster wheels any more.
>
> Rick “the coach is now Redhead-driveable” Denney
>
>
>
> On Fri, Sep 13, 2019 at 1:23 PM Richard Denney wrote:
>
>> Both me and the Redhead’s uncle hope so.
>>
> --
> '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 #347916 is a reply to message #347703] |
Mon, 16 September 2019 08:12 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Senior Member |
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My coach has a fairly long pedal travel, but when it hits the brakes, it is solid and above the floor... and has no sponginess and stops properly (It ain't my Soul, but it ain't awful).
The idea that one needs a bit of runout to back the pads up is false. The seal in the caliper is square, not round. It displaces slightly outward when brakes are applied, and retracts the pad a few thousandths when the pressure in the caliper is relieved. When Mac's supported an F Production Spridget driven by our inspector, we used a tool post grinder and a jig to get the rotors completely even all the way around, and got them to basically no runouit on the car. Do this and drive the car and the difference is noticeable on brake application. Worth a few tenths of a second around Road Atlanta - a noticeable advantage in class racing.
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: [GMCnet] Brake bleeding--new MC and rear disks -- No Longer GMCMH [message #347917 is a reply to message #347916] |
Mon, 16 September 2019 08:28 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Senior Member |
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That "few tenths of a second..." reminded me of last night's conversation
with my son, Alan. Seems he participated yesterday in an autocross at Road
Atlanta. Won best time of the day and best average time. Then he told me
that the last run, his best, was made with only 3 cylinders firing in his
Ford Focus, due to a blown head gasket. Made me comment "Maybe it's a clue
that you need to slow down a little...". "I think maybe you're right."
:-) It ain't always "the faster the better".
Ken H.
On Mon, Sep 16, 2019 at 9:14 AM Johnny Bridges via Gmclist <
gmclist@list.gmcnet.org> wrote:
> My coach has a fairly long pedal travel, but when it hits the brakes, it
> is solid and above the floor... and has no sponginess and stops properly (It
> ain't my Soul, but it ain't awful).
> The idea that one needs a bit of runout to back the pads up is false. The
> seal in the caliper is square, not round. It displaces slightly outward
> when brakes are applied, and retracts the pad a few thousandths when the
> pressure in the caliper is relieved. When Mac's supported an F Production
> Spridget driven by our inspector, we used a tool post grinder and a jig to
> get the rotors completely even all the way around, and got them to
> basically no runouit on the car. Do this and drive the car and the
> difference is noticeable on brake application. Worth a few tenths of a
> second
> around Road Atlanta - a noticeable advantage in class racing.
>
> --johnny
> --
> Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
> Braselton, Ga.
> I forgive them all, save those who hurt the dogs. They must answer to me
> in hell
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
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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 #347919 is a reply to message #347916] |
Mon, 16 September 2019 10:34 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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Absolutely imperative that the rotor runout be kept to a minimum. "0"
degrees is the goal. Absolutely, positively, no more than .010". Turn them
on the rig if removing them and realigning them on the hubs doesn't help.
GMC hubs are massive and somewhat crudely executed. Some are unacceptably
out of spec.
Jim Hupy
Salem, Oregon
On Mon, Sep 16, 2019, 6:14 AM Johnny Bridges via Gmclist <
gmclist@list.gmcnet.org> wrote:
> My coach has a fairly long pedal travel, but when it hits the brakes, it
> is solid and above the floor... and has no sponginess and stops properly (It
> ain't my Soul, but it ain't awful).
> The idea that one needs a bit of runout to back the pads up is false. The
> seal in the caliper is square, not round. It displaces slightly outward
> when brakes are applied, and retracts the pad a few thousandths when the
> pressure in the caliper is relieved. When Mac's supported an F Production
> Spridget driven by our inspector, we used a tool post grinder and a jig to
> get the rotors completely even all the way around, and got them to
> basically no runouit on the car. Do this and drive the car and the
> difference is noticeable on brake application. Worth a few tenths of a
> second
> around Road Atlanta - a noticeable advantage in class racing.
>
> --johnny
> --
> Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
> Braselton, Ga.
> I forgive them all, save those who hurt the dogs. They must answer to me
> in hell
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
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