Brakes on a MCI 5B

[richardkillmon]

Hello,

Can anyone explain somethings on my brake system.
In the front driver side is an second hose that looks like it does nothing, attached to the air chamber, what does it do?
I have worked on brakes on tractor trailer that you must cage or lock the ram to remove. When I removed all the air lines the air chamber stayed retracted. (which is not the engaged position for safety) Once I put the new chamber on, it was retracted , which is not the why to set the brakes. Once I hooked all the lines, it worked just perfect. they lock when the air is low. Is this normal?

Thanks

Rick

[buswarrior]

Where to begin?

Find a comfortable chair and read about DD3 brake chambers, both Bendix and MCI have a lot of things you need to read.

That is NOT a spring brake chamber. Totally different system and parts.

Everything you think you know about brakes will get you into deep trouble with that bus.

Happy coaching!
Buswarrior

[richard5933]

Someone posted this link on one of the bus sites recently:

http://www.mcicoach.com/fyiFromMci/maintMatters/0215.htm

Hope it helps. Take your time reading through it - it contains lots of information.

[chessie4905]

Here is one source for parts or rebuilt units.

http://busfixx.tripod.com/busservice/id31.html
Sometimes severe internal corrosion can make these units un-rebuildable. Although expensive, it often makes sense to purchase new or rebuilt while they are still available. Bendix discontinued them about 10 years ago. Also, if you go to the Bendix site, they have great pictures, breakdowns, and and operational design.

[bevans6]

This post, from a month ago, explains MC-5c air brakes and operation in some detail.  Your 5B will be quite similar in most respects.

https://www.busconversionmagazine.com/forum/index.php?topic=34002.msg389923#msg389923

Brian

[buswarrior]

And 1976 is a complicated time as to how it was plumbed.

Be sure you have the EXACTLY correct air schematic for your EXACT unit number.

Over the top of those years, the MC8 had 8 different air schematics.

Happy coaching!
Buswarrior

[bevans6]

Exactly, you need the schematic for your bus.  That was when dual system air brakes were coming into mandated play.  On MCI's of a certain vintage the emergency tank/dd3/dual foot valve with shuttle valve was the dual system.  Later, a more currently normal two service tank dual system, one tank for front brakes and one for rear brakes, was added.  I'm not sure what the earlier versions were like, I know the use of air dryers changed, the location of the wet and dry tanks swapped, the location that the air pressure gauge reads from changed from Aux system to Dry tank.  But I don't know when.

[buswarrior]

And there were buses built under federally granted exemptions, which look very similar to the pre- FMVSS 121 buses.

If looking back is hard, imagine what is was like in the moment?

Orders to disconnect and render useless the original "anti-skid" machinery, that had only just been regulated...

"Anti-lock brakes" would not return to regulation until the 90's... what a boondoggle of legislative arrogance vs technical limitations...

Happy coaching!
Buswarrior

[richardkillmon]

thank you all