Home » Public Forums » GMCnet » [GMCnet] gravity bleed procedure? (semi-stranded)
| [GMCnet] gravity bleed procedure? (semi-stranded) [message #307736] |
Sat, 24 September 2016 11:09  |
Ek_Lektro
Messages: 167
Registered: March 2011
Karma: 2
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Senior Member |
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Good morning GMC’ers,
After a 6 hour drive, and RIGHT as i pulled into our campsite, the brakes gave out, and the light came on. (At least we made it to the spot!) (But… the campsite is on a hill… extra points)
There’s brake fluid all over the inside of the rear-most driver’s side wheel, and i’m pretty sure the leak is coming from the rusty line itself, but not 100% sure. Do they ever leak from the cylinders themselves? To see if i could confirm the leak spot, i tried adding fluid and pumping the brakes, but there must be too much air in the lines, ‘cause i’m not getting any additional visible leakage this way.
We’re out in the middle of nowhere, and i understand that for an emergency repair, i could carefully kink the offending line, do a gravity bleed, and run on 5 brakes; but fortunately a friend was arriving to the camp site one day behind, and was able to pick up a brake line, extra fluid, 3/8” flare nut wrench.. and PB Blaster. So i soaked the nut and adjuster last night, ready to go.
I’ve assisted with brake jobs many times over the years, but i was always the guy pumping the pedal up front, so i’ve never done the bleeder screw myself! My guess is that i loosen it up counter clockwise, and that once fluid comes out without bubbles, tighten it back up?
And as far as “gravity bleed”, Do i need to jack up the front? or is the height of the master cylinder enough that gravity should take its course?
Since the fluid was not low in the rear chamber, i’m guessing i don’t need to bleed the fronts, but probably will need to bleed the other side, rears?
And.. if i can get a friend to do the brake pumping, is this method more effective at all with the engine running?
Many thanks for any quick tips… (and i’m on the digest version of the list, so direct replies appreciated :)
Standing by, ready to go, cheers
Greg
SolarSonic (semi-stranded at the Symbiosis Festival :)
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| Re: [GMCnet] gravity bleed procedure? (semi-stranded) [message #307738 is a reply to message #307736] |
Sat, 24 September 2016 11:36  |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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Inside of the wheel sounds like wheel cylinder to me. Saturated linings. If
one wheel cylinder has failed, others aren't far behind it. Disconnect the
hard line from the wheel cylinder and screw the fitting into a female
matching fitting with a short piece of line crimped off on it to seal up
the system. Bleed the rear brake system, drive it to someplace where you
can jack it up and remove the drums ( repair facility) and rebuild the rear
brakes. All of them. Check the fronts too. Bleed the entire system.
Jim Hupy
On Sep 24, 2016 9:14 AM, "Ek_Lektro" wrote:
> Good morning GMC’ers,
> After a 6 hour drive, and RIGHT as i pulled into our campsite, the brakes
> gave out, and the light came on. (At least we made it to the spot!) (But…
> the campsite is on a hill… extra points)
> There’s brake fluid all over the inside of the rear-most driver’s side
> wheel, and i’m pretty sure the leak is coming from the rusty line itself,
> but not 100% sure. Do they ever leak from the cylinders themselves? To
> see if i could confirm the leak spot, i tried adding fluid and pumping the
> brakes, but there must be too much air in the lines, ‘cause i’m not getting
> any additional visible leakage this way.
>
> We’re out in the middle of nowhere, and i understand that for an emergency
> repair, i could carefully kink the offending line, do a gravity bleed, and
> run on 5 brakes; but fortunately a friend was arriving to the camp site one
> day behind, and was able to pick up a brake line, extra fluid, 3/8” flare
> nut wrench.. and PB Blaster. So i soaked the nut and adjuster last night,
> ready to go.
>
> I’ve assisted with brake jobs many times over the years, but i was always
> the guy pumping the pedal up front, so i’ve never done the bleeder screw
> myself! My guess is that i loosen it up counter clockwise, and that once
> fluid comes out without bubbles, tighten it back up?
>
> And as far as “gravity bleed”, Do i need to jack up the front? or is the
> height of the master cylinder enough that gravity should take its course?
> Since the fluid was not low in the rear chamber, i’m guessing i don’t need
> to bleed the fronts, but probably will need to bleed the other side, rears?
> And.. if i can get a friend to do the brake pumping, is this method more
> effective at all with the engine running?
>
> Many thanks for any quick tips… (and i’m on the digest version of the
> list, so direct replies appreciated :)
> Standing by, ready to go, cheers
> Greg
> SolarSonic (semi-stranded at the Symbiosis Festival :)
>
>
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
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| Re: [GMCnet] gravity bleed procedure? (semi-stranded) [message #307739 is a reply to message #307736] |
Sat, 24 September 2016 11:47 |
bdub
Messages: 1578
Registered: February 2004
Location: Central Texas
Karma: 5
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Senior Member |
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No need to run engine for bleeding brakes.
Fill master cylinder with fluid, replace lid,
Pump up brake pedal and hold, open the bleeder, brake pedal goes to the
floor, close bleeder,
Pump up brake pedal and hold, open the bleeder, brake pedal goes to the
floor, close bleeder,
again
again
Open master, make sure there's plenty of fluid, (don't let it run out)
Pump up brake pedal and hold, open the bleeder, brake pedal goes to the
floor, close bleeder,
Pump up brake pedal and hold, open the bleeder, brake pedal goes to the
floor, close bleeder,
Repeat until there is no more air evident in the line.
Top off master with fluid.
Normally this is done for each wheel, starting with the one furthest from
the master. Your situation might be an exception.
Gravity bleed is for overnight or more.
Other replies solicited to Ek_Lektro
bdub
On Sat, Sep 24, 2016 at 11:09 AM, Ek_Lektro wrote:
> Good morning GMC’ers,
> After a 6 hour drive, and RIGHT as i pulled into our campsite, the brakes
> gave out, and the light came on. (At least we made it to the spot!) (But…
> the campsite is on a hill… extra points)
> There’s brake fluid all over the inside of the rear-most driver’s side
> wheel, and i’m pretty sure the leak is coming from the rusty line itself,
> but not 100% sure. Do they ever leak from the cylinders themselves? To
> see if i could confirm the leak spot, i tried adding fluid and pumping the
> brakes, but there must be too much air in the lines, ‘cause i’m not getting
> any additional visible leakage this way.
>
> We’re out in the middle of nowhere, and i understand that for an emergency
> repair, i could carefully kink the offending line, do a gravity bleed, and
> run on 5 brakes; but fortunately a friend was arriving to the camp site one
> day behind, and was able to pick up a brake line, extra fluid, 3/8” flare
> nut wrench.. and PB Blaster. So i soaked the nut and adjuster last night,
> ready to go.
>
> I’ve assisted with brake jobs many times over the years, but i was always
> the guy pumping the pedal up front, so i’ve never done the bleeder screw
> myself! My guess is that i loosen it up counter clockwise, and that once
> fluid comes out without bubbles, tighten it back up?
>
> And as far as “gravity bleed”, Do i need to jack up the front? or is the
> height of the master cylinder enough that gravity should take its course?
> Since the fluid was not low in the rear chamber, i’m guessing i don’t need
> to bleed the fronts, but probably will need to bleed the other side, rears?
> And.. if i can get a friend to do the brake pumping, is this method more
> effective at all with the engine running?
>
> Many thanks for any quick tips… (and i’m on the digest version of the
> list, so direct replies appreciated :)
> Standing by, ready to go, cheers
> Greg
> SolarSonic (semi-stranded at the Symbiosis Festival :)
>
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bdub
'76 Palm Beach/Central Texas
www.bdub.net
www.gmcmhphotos.com
www.gmcmotorhomemarketplace.com
www.gmcmhregistry.com
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www.facebook.com/groups/gmcmm
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| Re: [GMCnet] gravity bleed procedure? (semi-stranded) [message #307741 is a reply to message #307736] |
Sat, 24 September 2016 12:27 |
Ek_Lektro
Messages: 167
Registered: March 2011
Karma: 2
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Senior Member |
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On Sat, Sep 24, 2016 at 11:36 AM, James Hupy wrote:
> Inside of the wheel sounds like wheel cylinder to me. Saturated linings. If
> one wheel cylinder has failed, others aren't far behind it. Disconnect the
> hard line from the wheel cylinder and screw the fitting into a female
> matching fitting with a short piece of line crimped off on it to seal up
> the system.
hey James, thanks for the tip.
and i should’ve put a little more detail into my original post,
but a ‘bit' more of the fluid seems to be coming from an area where the rusty line is rubbing against the back of the wheel mount. couldn’t visibly see a leak coming from there specifically, but if i had to put my money on it.. well.....
and with the wheel turning around, i think a drip is gonna make the inside of the wheel mostly wet. so i’m 90% sure its just the line,… (also ‘cause i’m pretty sure the cylinders were changed about 5 yrs ago, during the last rear brake job,.. though that doesn’t necessarily mean anything!)
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| Re: [GMCnet] gravity bleed procedure? (semi-stranded) [message #307750 is a reply to message #307736] |
Sat, 24 September 2016 15:08 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Senior Member |
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Greg,
I have done a lot of both gravity and vacuum bleeding.
Somewhere there will be an high school auto shop teacher beating his head against a wall, but....
Given you know you blew a brake line, start with that wheel first. You may not need to bled the others.
After the line is replaced, leave that wheel cylinder open. If you have some clear tubing that is a help.
Fill the master cylinder about twice, then run around and see if solid fluid is coming out.
If it is, close the bleeder and try the brakes.
If it isn't go refill the master cylinder and let fluid run while you watch. If you don't see solid fluid in a few minute, close the bleeder and check the reservoir level. Top it up and let it run again.
When you get bored, test the pedal feel. If it is pretty solid, try driving it.
If the pedal does not got to the floor, drive it home and then you can do a good bleed.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: [GMCnet] gravity bleed procedure? (semi-stranded) [message #307763 is a reply to message #307736] |
Sat, 24 September 2016 20:42 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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That happened to me in Southern Louisiana leaving a rally. I went to the closest auto parts store and bought either a cap or a plug and sealed off the line for that wheel only. Then I filled up the master cylinder and opened the cap / plug until the fluid drained out. I let it run while and kept the master cylinder filled up so no new air could get in the line. After about 1/2 small can of fluid ran through it I closed the cap / plug. I drove it home to NW Indiana on 3 rear brakes and never knew the difference.
That was a lot easier than trying to repair it on the spot. Later I replaced all 4 rear wheel cylinders. They are cheap.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] gravity bleed procedure? (semi-stranded) [message #307779 is a reply to message #307736] |
Sun, 25 September 2016 08:58 |
kingd
Messages: 592
Registered: June 2004
Karma: 2
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Senior Member |
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To all reading and contributing to this thread, as the "posters" brake warning light
came on, might he need to "reset" the shuttle in the combination valve before he can get
fluid to the rear brakes? Will someone who knows about this please post how "Ek" can tell
if the combination valve needs resetting. If the brake light is still on with the engine running
is that an indication the valve is "overcenter"?
DAVE KING
lurker, wannabe
Toronto, Ontario, Canada
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