Brake Issue

[Beluga Bus]

One the last leg home the brakes started feeling different. On 0-50% pedal pressure all was good, but more than 50% pressure and the pedal would go to the floor and 100% brakes were applied. There was no modulation between 50-100%. Is this an issue with the treadle value or should I be looking somehere else?

Thanks, Matt

[Sunchaser Art]

Geez Matt-
That's an old coach and perplexing question.  Without throwing a bunch of parts at it (foundation and air stuff), I'd be inclined to put a gauge in one of the 1/4" pipe fittings that are available and see what the application air pressure is when it happens.  You'll probably need an assistant to watch the gauge when it happens, and you may need to try a few different places. 

That would be a fun project though--just don't run you our your helper over!

Art

[chessie4905]

Being that old, I'd replace treadle valve or get a rebuild kit.

[TomC]

Sounds like your brakes are out of adjustment.

[Utahclaimjumper]

 Check your slack adjusters,, they could be nearing a point of over center position or the brake cams could be trying the same thing,,check the slack angles at full application to,,should be 90 degrees.>>>Dan

[Dave5Cs]

Matt when this happens does your air gauge on the dash go to  zero or does it stay with regular pressure?

[Beluga Bus]

Thanks for all the replies. First thing I did was to check the slack adjusters, all were good. When this happens air pressure drops by 6-8 psi about the same as if I floored the brakes. Going to take a closer look today, will check psi at the chambers, and movment of the arms.
Thanks Matt

[Sunchaser Art]

Matt-
I'm guessing you have something like an E-2 or E-3 foot valve.  I wonder if the spring or plunger is hanging up inside the foot valve.  You might not be able to feel it with your foot, but if it's hung a bit, you could probably feel it fairly easily with your hand and no air in the system.

[Beluga Bus]

Nice call on the slack adjuster. When my son operated the brakes the right front cylinder bearly moved, and was already past 90 degrees. The clevis pin was rusted and didnt allow the cylinder to retract all the way. Freed, cleaned and lubed the pin and readjusted the slack adjuster and now its operating normally. At full brakes I was at about 30% on the S cams.

Sunchaser it is a D-1 foot valve. If anyone has a spare or rebuild kit, I would be happy to buy it.

Thanks, Matt

[Utahclaimjumper]

Looks like the time to check & service them all Matt.>>>Dan

[Utahclaimjumper]

 Matt,, We are in Hungry Horse, Montana,,when are you getting up into the north country again??>>>Dan

[Beluga Bus]

Dan, seviced and replaced some parts on the rears last winter. I was just up north in central Oregon for the eclipse, but cut arcoss to the coast and took the 101 and 1 south. Luckily the brakes were 100% for that drive, too many 10mph curves. I didn't have this issue till i was cutting across to the 5.

I'm not going to make it to the BCI rally in Wyoming, however I shoukd make it to the Dam rally in November.

Matt

[chessie4905]

Here's some info if you want to upgrade.

http://busnut.com/forum/index.php?topic=1092.0

[Red Rider]

Hey Matt, I for one know how detailed your work on Beluga is. Scarry situation. Glad you got to the bottom of this problem. We will be missing you at Star Valley.

[Beluga Bus]

Chessie, thanks for the link. I will put that high on the list for furture projects!

Yea Mike, bummed about missis Wyoming. Hope its a great rally for you guys.

Matt