GMCforum: GMCnet » Brake pedal travel

Home » Public Forums » GMCnet » Brake pedal travel

Show: Today's Messages :: Polls :: Message Navigator

Brake pedal travel [message #311537]

Sun, 18 December 2016 08:33

Luvn737s

Messages: 1106
Registered: June 2007

Karma: 2

Senior Member

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

Report message to a moderator

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

Senior Member

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

Report message to a moderator

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

Senior Member

Water in brake fluid. Trapped air. Change fluid and be happy.
Tom, MS II

2012 Phoenix Cruiser model 2552 KA4CSG

Report message to a moderator

Re: Brake pedal travel [message #311542 is a reply to message #311537]

Sun, 18 December 2016 16:08

Matt Colie

Messages: 8547
Registered: March 2007
Location: S.E. Michigan

Karma: 7

Senior Member

Luvn737s wrote on Sun, 18 December 2016 09:33

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,

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

Report message to a moderator

Re: Brake pedal travel [message #311543 is a reply to message #311537]

Sun, 18 December 2016 19:34

Luvn737s

Messages: 1106
Registered: June 2007

Karma: 2

Senior Member

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

Report message to a moderator

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

Senior Member

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.

Report message to a moderator

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

Senior Member

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.

Report message to a moderator

Re: Brake pedal travel [message #311546 is a reply to message #311543]

Mon, 19 December 2016 08:03

Matt Colie

Messages: 8547
Registered: March 2007
Location: S.E. Michigan

Karma: 7

Senior Member

Luvn737s wrote on Sun, 18 December 2016 20:34

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,

You have that answer from Terry, but I have been vacuum (and gravity) bleeding for years because so many of my vehicles were simply not amenable to pressure bleeding.

Very early on I discovered that the leakage on the threads is a problem two ways. The corrosion caused by the brake fluid in the threads may not be a big issue in Arizona (I thought I remembered you living the NW), but the leakage while vacuum bleeding can be deceiving and cause you to bleed way more than might be needed.
To deal with this, either wrap the threads with teflon tape (any color) (or I used to glom them up with a teflon filled pipe thread dope). The teflon tape is cleaner and neater. It works well if you have a spare bleed screw so you can remover and replace. Then you can clean that one and use it for the next. The amount of future grief this will prevent is amazing. I can't even remember the last time I broke (common thing in Michigan) a bleed screw in one of my own vehicles.

If the little rubber caps are gone, they are good to have.

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

Report message to a moderator

Re: Brake pedal travel [message #311547 is a reply to message #311544]

Mon, 19 December 2016 10:28

A Hamilto

Messages: 4508
Registered: April 2011

Karma: 39

Senior Member

Bullitthead wrote on Sun, 18 December 2016 23:35

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.

If the rear brakes stay adjusted (either by the self adjusters or manually), the fluid in the master cylinder will never be depleted by wear of the shoes. Depletion of the master cylinder results from the wear of the disk brake pads on the front. On the OEM system (and if there are no leaks) the master cylinder reservoir holds enough fluid to allow the front pads to wear completely out without getting too low of fluid.

But all of that goes out the window when the vehicle gets to be 40 years old and things don't work like they did from the factory, or POs have done stuff that is non-OEM.

Report message to a moderator

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

Senior Member

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

Report message to a moderator

Re: Brake pedal travel [message #311845 is a reply to message #311537]

Thu, 05 January 2017 16:43

Luvn737s

Messages: 1106
Registered: June 2007

Karma: 2

Senior Member

Fwd master cyl reservoir almost empty. Filled and seems fine. No obvious external leaks.

Randy
1973 26' Painted Desert
Ahwatukee (Phoenix) AZ

[Updated on: Thu, 05 January 2017 16:44]

Report message to a moderator

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

Senior Member

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

Report message to a moderator

Re: Brake pedal travel [message #311848 is a reply to message #311845]

Fri, 06 January 2017 07:22

Matt Colie

Messages: 8547
Registered: March 2007
Location: S.E. Michigan

Karma: 7

Senior Member

Luvn737s wrote on Thu, 05 January 2017 17:43

Fwd master cyl reservoir almost empty. Filled and seems fine. No obvious external leaks.

Randy,

That reservoir should not go down unless there is a leak. Have adjusted the rear brakes?
If you don't want to climb under there at least find a big area that you can jam the brakes while backing up.
If the brakes got that far out, it can really truly take a dozen stops to set the brakes up right.
When doing this, expect to rearrange everything that is loose.

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

Report message to a moderator

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

Karma: 5

Senior Member

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

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

Senior Member

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/
>
> _______________________________________________
> 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

Report message to a moderator

Re: [GMCnet] Brake pedal travel [message #311859 is a reply to message #311852]

Fri, 06 January 2017 11:24

A Hamilto

Messages: 4508
Registered: April 2011

Karma: 39

Senior Member

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.

Report message to a moderator

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

Karma: -62

Senior Member

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."
>
> _______________________________________________
> 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

Report message to a moderator

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

Senior Member

James Hupy wrote on Fri, 06 January 2017 12:11

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

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.

Report message to a moderator

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

Senior Member

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

Report message to a moderator

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

Senior Member

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

Report message to a moderator

Pages (2): [1 2 › »]

Previous Topic:	[GMCnet] GA weather
Next Topic:	[GMCnet] Newbie's. And maybe all. I have a GMC. Now what?

Goto Forum:

-=] Back to Top [=-

Current Time: Fri Sep 27 22:11:34 CDT 2024

Total time taken to generate the page: 0.02519 seconds