Brake pedal travel [message #311537] |
Sun, 18 December 2016 08:33 |
Luvn737s
Messages: 1106 Registered: June 2007
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Confession - I have not been driving my coach as much as I should.
Stock Front Disk / Rear Drum setup and prefer to stay that way.
I took the coach out and the pedal seems to go almost to the floor before any braking resistance is felt. With engine off brake pedal gets firm after pumping it and goes down after starting up. All brake flex hoses replaced with teflon about 5 years ago. No obvious external fluid leaks. Booster line intact and connected. No brake shoe/pad noise.
Any ideas as to what these symptoms point to?
Randy
1973 26' Painted Desert
Ahwatukee (Phoenix) AZ
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Re: Brake pedal travel [message #311538 is a reply to message #311537] |
Sun, 18 December 2016 09:15 |
JohnL455
Messages: 4447 Registered: October 2006 Location: Woodstock, IL
Karma: 12
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I would look at the more of the basics first. Fluid level and condition (clear). You may have a rear cylinder leak and that won't hit the ground for a while. Hidden leak. Maybe back up in a parking lot and firm apply to adjust rears several times. Or the booster gives enough assist to drop the pedal-- that part is odd An internal MC leak past seals can also cause this.
John Lebetski
Woodstock, IL
77 Eleganza II
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Re: Brake pedal travel [message #311539 is a reply to message #311538] |
Sun, 18 December 2016 09:20 |
tphipps
Messages: 3005 Registered: August 2004 Location: Spanish Fort, AL
Karma: 9
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Water in brake fluid. Trapped air. Change fluid and be happy.
Tom, MS II
2012 Phoenix Cruiser model 2552
KA4CSG
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Re: Brake pedal travel [message #311542 is a reply to message #311537] |
Sun, 18 December 2016 16:08 |
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Matt Colie
Messages: 8547 Registered: March 2007 Location: S.E. Michigan
Karma: 7
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Luvn737s wrote on Sun, 18 December 2016 09:33Confession - I have not been driving my coach as much as I should.
Stock Front Disk / Rear Drum setup and prefer to stay that way.
I took the coach out and the pedal seems to go almost to the floor before any braking resistance is felt. With engine off brake pedal gets firm after pumping it and goes down after starting up. All brake flex hoses replaced with teflon about 5 years ago. No obvious external fluid leaks. Booster line intact and connected. No brake shoe/pad noise.
Any ideas as to what these symptoms point to?
Randy,
With no vacuum source(?) the pedal will get real hard after a pump or two, but if you were rolling, you would also realize that you then have no brakes.....
After you check the fluid level, do this test with the engine idling:
- Press the pedal once and note the travel or distance from floor.
- Pump the pedal three/four times and hold the last.
?? Did the pedal come up ??
If yes, it could be rear brake adjustment.
If no, it could be air in the system.
- Wait 15 minutes and try again. (It can take a while for the shoes to move back.)
?? Same result ?? See above.
To adjust the rear brakes, (hope no bozo removed the self adjusters) go to an empty lot. Put everything that is loose and or fragile on the floor or someplace it can't fall/fly.
- Reverse Smartly, Jam on the Brakes.
- Repeat four times. The self adjusters cannot over adjust the brakes.
- Wait a bit again and asses the pedal travel now.
If it didn't get better, then you do probably have air in the system. I don't know how it happens, but I have had air accumulate in the brakes of a vehicle that I had bled to solid some time before. It is rare, but it does happen.
Let us know how this worked out.
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: Brake pedal travel [message #311543 is a reply to message #311537] |
Sun, 18 December 2016 19:34 |
Luvn737s
Messages: 1106 Registered: June 2007
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I'd like to bleed them with my Mityvac ( pedal helpers always seem to find something better to do halfway through). Does it matter if the pedal is up or fully depressed when bleeding from the wheel?
Randy
1973 26' Painted Desert
Ahwatukee (Phoenix) AZ
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Re: Brake pedal travel [message #311544 is a reply to message #311543] |
Sun, 18 December 2016 23:35 |
Bullitthead
Messages: 1411 Registered: November 2013
Karma: 5
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The pedal needs to be up when bleeding from the wheel. Otherwise there is no path for the fluid to flow from the reservoir. When there is a big system (like 4 wheel cylinders) coupled with a small reservoir,(like in the GMC), the level in the reservoir needs to be closely monitored as the shoes wear. This is especially evident when breaking in new brake shoes or if the self adjusters are not working properly or getting used enough as the shoes wear.
Terry Kelpien
ASE Master Technician
73 Glacier 260
Smithfield, Va.
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Re: Brake pedal travel [message #311545 is a reply to message #311544] |
Sun, 18 December 2016 23:44 |
Bullitthead
Messages: 1411 Registered: November 2013
Karma: 5
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Maybe you should jack up each side real quick and spin the wheels to see if the brakes are all properly adjusted. If one or more is not adjusted out for wear, adjusting it manually may force air at the top of the system back out of the master cylinder and into the reservoir. Then you wont have to bleed the system. This same scenario just happened to me and it was just the fluid going low because the shoes were wearing in and I had not been doing my dutiful back up stops for the amount of braking that I did over the past several months.
Terry Kelpien
ASE Master Technician
73 Glacier 260
Smithfield, Va.
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Re: Brake pedal travel [message #311548 is a reply to message #311537] |
Mon, 19 December 2016 12:09 |
JohnL455
Messages: 4447 Registered: October 2006 Location: Woodstock, IL
Karma: 12
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If your MC is good now, there is a good chance it will soon fail. Moving the pedal to push pistons to areas of the bore "that have never been charted" tends to destroy the lip seals as they scrape over crusty bore. So be aware and best to use less than full depressions when bleeding or testing.
John Lebetski
Woodstock, IL
77 Eleganza II
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Re: Brake pedal travel [message #311847 is a reply to message #311845] |
Fri, 06 January 2017 06:16 |
tphipps
Messages: 3005 Registered: August 2004 Location: Spanish Fort, AL
Karma: 9
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OEM master cylinder front reservoir supplies fluid for rear brakes. Might be time to check rear brakes.
Preaching to the choir.
Tom, MS II
2012 Phoenix Cruiser model 2552
KA4CSG
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Re: Brake pedal travel [message #311850 is a reply to message #311845] |
Fri, 06 January 2017 09:20 |
lqqkatjon
Messages: 2324 Registered: October 2010 Location: St. Cloud, MN
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my rear brakes leaked for about 2 years. I checked and topped off the front reservoir or the master cylinder before every trip, and when I stopped. sometimes it was fine, sometimes I added a a bit of fluid. I never noticed any external fluid leakage, but when I finally did re-build the rear brakes, you could tell a few of the brake cylinders were leaking.
Chances are you have a rear brake cylinder leaking.
Jon Roche
75 palm beach
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/
[Updated on: Fri, 06 January 2017 09:21] Report message to a moderator
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Re: [GMCnet] Brake pedal travel [message #311852 is a reply to message #311850] |
Fri, 06 January 2017 09:34 |
James Hupy
Messages: 6806 Registered: May 2010
Karma: -62
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Anytime you lose fluid in the master cylinder reservoir, you have a leak.
Brakes are THE MOST CRITICAL SYSTEM in your coach. They need to be 100% all
the time. People's lives depend upon their condition. Find that leak, and
repair it, sooner than later.
Jim Hupy
Salem, Or
78 GMC ROYALE 403
On Jan 6, 2017 7:26 AM, "Jon Roche" wrote:
> my rear leaked for about 2 years. I checked and topped it off before
> every trip, and when I stopped. sometimes it was fine, sometimes I added
> a a
> bit of fluid. I never noticed any external fluid leakage, but when I
> finally did re-build the rear brakes, you could tell a few of the brake
> cylinders were leaking.
>
>
> Chances are you have a rear brake cylinder leaking.
> --
> Jon Roche
> 75 palm beach
> St. Cloud, MN
> http://lqqkatjon.blogspot.com/
>
> _______________________________________________
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Re: [GMCnet] Brake pedal travel [message #311861 is a reply to message #311859] |
Fri, 06 January 2017 12:11 |
James Hupy
Messages: 6806 Registered: May 2010
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In a stock unmolested brake system in a GMC MOTORHOME, the front reservoir
is for the rear brakes, and the back reservoir is for the front disc
brakes, as the front pads wear, the level in the reservoir drops
accordingly. I don't believe that is what is happening on this particular
coach. NEVER ASSUME ANY FLUID LOSS IS NORMAL. VERIFY WHAT IS GOING ON.
YOUR LIFE AND LIVES OF OTHERS, MAY DEPEND UPON IT.
JIM HUPY
Salem, Or
78 GMC ROYALE 403
On Jan 6, 2017 9:25 AM, "A." wrote:
> James Hupy wrote on Fri, 06 January 2017 09:34
>> Anytime you lose fluid in the master cylinder reservoir, you have a
> leak. ...
> As the front pads wear, the fluid in its reservoir drops. On the OEM
> system, the front reservoir is the rear brakes. If the system has been
> altered so
> that the front reservoir is the front brakes, there is a good chance a
> drop in fluid means nothing except that the pads are wearing.
>
> Hard to diagnose anything on a 40 yo vehicle (that may not be all OEM)
> without complete information.
> --
> 73 23' Sequoia 4 Sale
> 73 23' CanyonLands Parts Unit 4 Sale
> Upper Alabama
> "Highest price does not guarantee highest quality."
>
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Re: [GMCnet] Brake pedal travel [message #311864 is a reply to message #311861] |
Fri, 06 January 2017 14:25 |
A Hamilto
Messages: 4508 Registered: April 2011
Karma: 39
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James Hupy wrote on Fri, 06 January 2017 12:11In a stock unmolested brake system in a GMC MOTORHOME, the front reservoir
is for the rear brakes, and the back reservoir is for the front disc
brakes, as the front pads wear, the level in the reservoir drops
accordingly. I don't believe that is what is happening on this particular
coach. NEVER ASSUME ANY FLUID LOSS IS NORMAL. VERIFY WHAT IS GOING ON.
YOUR LIFE AND LIVES OF OTHERS, MAY DEPEND UPON IT.
JIM HUPY
Salem, Or
78 GMC ROYALE 403 Yep. Better safe than sorry, or worse.
Mostly I wanted to clarify that the fluid level in a reservoir that feeds disc brakes will drop without a leak. That's how they "self-adjust".
Now I don't know if the one that started this discussion has rear drums or discs, or if the lines have been reversed or the shoes are not self-adjusting and one or more wheel cylinders are not being pulled back (cylinder holding extra fluid).
Fluid needs to be replenished as discs wear, and drums need to be serviced if the reservoir needs fluid.
Just trying to stop a noob from panicking if the reservoir for disc brakes needs fluid.
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Re: Brake pedal travel [message #311868 is a reply to message #311537] |
Fri, 06 January 2017 17:21 |
Luvn737s
Messages: 1106 Registered: June 2007
Karma: 2
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Thanks for the description of which reservoir feeds which brakes. I'll check for a leaking wheel cylinder in the back.
Randy
1973 26' Painted Desert
Ahwatukee (Phoenix) AZ
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Re: Brake pedal travel [message #312454 is a reply to message #311537] |
Tue, 24 January 2017 14:25 |
Luvn737s
Messages: 1106 Registered: June 2007
Karma: 2
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Senior Member |
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Looked under the coach for signs of fluid leaking out of any of the cylinders. Could fluid be in the booster?
Randy
1973 26' Painted Desert
Ahwatukee (Phoenix) AZ
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