| [GMCnet] Fuel/Spark/Dragging Brakes [message #184632] |
Sat, 15 September 2012 19:27  |
Dolph Santorine
Messages: 1236
Registered: April 2011
Location: Wheeling, WV
Karma: -41
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Senior Member |
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I'm trying to get everything together for the trip to Iowa, and I'm down to troubleshooting a performance issue.
I'm running four wheel discs. The temperature of the disc's after a short trip on the interstate tonight are: (from the handy-dandy HF IR thermometer)
Rear - 450
Middle - 357
Fronts - 207
That was not immediately after braking, but after I drove the coach home and parked it.
I have the mechanical line lock to provide for parking brake (from JimK). I'm pretty certain its dis-engaging (but will double check it again tomorrow).
I checked the choke to make certain it's letting the secondaries on the Q-Jet open. (Last time I did anything serious with a Q-Jet, Jimmy Carter was President) It's properly adjusted.
I'll run it with the engine cover open tomorrow and visually check that the secondaries are opening.
I'm also going to put a fuel pressure gauge inline and see what kind of pressure is present at the inlet to the carb.
That leaves timing to look at, and it might have to invest in a timing light.
Suggestions? Thoughts? Are those brake disc temperatures indicative of a problem.
Any thoughts and help would be appreciated.
Dolph
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| Re: [GMCnet] Fuel/Spark/Dragging Brakes [message #184639 is a reply to message #184632] |
Sat, 15 September 2012 19:50  |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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Dolph, the front brake temps sound a little low. The rear brakes, drum or
disc, usually run hotter than the middle ones do. As the fronts do a major
Amount of the total you should expect them to be hotter. If the rotors are
uneven temps side to side, I would investigate more. Places to look would
be air in the system, or calipers not floating on the pins. JWIWD.
Jim Hupy
Salem, or
78 GMC ROYALE 403
On Sep 15, 2012 5:27 PM, "Dolph Santorine" <dolph@dolphsantorine.com> wrote:
> I'm trying to get everything together for the trip to Iowa, and I'm down
> to troubleshooting a performance issue.
>
> I'm running four wheel discs. The temperature of the disc's after a short
> trip on the interstate tonight are: (from the handy-dandy HF IR thermometer)
>
> Rear - 450
> Middle - 357
> Fronts - 207
>
> That was not immediately after braking, but after I drove the coach home
> and parked it.
>
> I have the mechanical line lock to provide for parking brake (from JimK).
> I'm pretty certain its dis-engaging (but will double check it again
> tomorrow).
>
> I checked the choke to make certain it's letting the secondaries on the
> Q-Jet open. (Last time I did anything serious with a Q-Jet, Jimmy Carter
> was President) It's properly adjusted.
>
> I'll run it with the engine cover open tomorrow and visually check that
> the secondaries are opening.
>
> I'm also going to put a fuel pressure gauge inline and see what kind of
> pressure is present at the inlet to the carb.
>
> That leaves timing to look at, and it might have to invest in a timing
> light.
>
> Suggestions? Thoughts? Are those brake disc temperatures indicative of a
> problem.
>
> Any thoughts and help would be appreciated.
>
>
> Dolph
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
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| Re: [GMCnet] Fuel/Spark/Dragging Brakes [message #184646 is a reply to message #184632] |
Sat, 15 September 2012 20:08 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Senior Member |
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Dolph,
Disregarding the necessity to coast to a stop before taking diagnostic
brake drag temperatures, think about the brake balance you'd like to have:
60% front/40% rear. The temperatures you're reporting say you're getting
about 20% front and 80% rear. That's NOT good.
Fill the MC reservoirs almost full, then have someone push the brake pedal
down firmly and release it while you watch the reservoir. There should be
a small disturbance in each reservoir when the pedal is released. If
there's none, the relief port is not being exposed, indicative of a
too-long push rod or other interference with fluid movement. If there's a
big surge, there's probably air in that system; it's expansion is "blowing"
the fluid out. You want, in fact, MUST have, just a little disturbance in
each reservoir caused by the pistons retracting slightly.
Ken H.
On Sat, Sep 15, 2012 at 8:27 PM, Dolph Santorine wrote:
> I'm trying to get everything together for the trip to Iowa, and I'm down
> to troubleshooting a performance issue.
>
> I'm running four wheel discs. The temperature of the disc's after a short
> trip on the interstate tonight are: (from the handy-dandy HF IR thermometer)
>
> Rear - 450
> Middle - 357
> Fronts - 207
>
> That was not immediately after braking, but after I drove the coach home
> and parked it.
>
> I have the mechanical line lock to provide for parking brake (from JimK).
> I'm pretty certain its dis-engaging (but will double check it again
> tomorrow).
> ...
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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] Fuel/Spark/Dragging Brakes [message #184688 is a reply to message #184682] |
Sun, 16 September 2012 08:26 |
Dolph Santorine
Messages: 1236
Registered: April 2011
Location: Wheeling, WV
Karma: -41
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Senior Member |
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Well, it's not the brakes.
Jacked it up. They spin fine.
Checked the disc temps after a roll to stop all at about 200.
Checked my Expedition the right and wrong ways. Consistent.
Dolph Santorine
Dolph@DolphSantorine.com
Excuse me for not being my usual wordy and sporadically verbose self. This message is sent from my iPhone.
No trees were killed in the sending of this message and few long dead dinosaurs were involved. A large number of electrons were terribly inconvenienced.
On Sep 16, 2012, at 8:56 AM, jerrod winter <jerrod_beth@msn.com> wrote:
>
>
> Doesn't the combination valve put initial priority to the rear brakes and then after a certain pressure is reached (500 psi???) start applying pressure to the front brakes?
>
> If that valve is still in the system and the brakes are only lightly used, could the rears be doing most of the work?
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