Air plumbing question on MCI

[bevans6]

My bus is a 1980 MCI, since they made various changes over the years.  My question relates to the air governor plumbing.  I have been redoing various hoses and just noticed that the reservoir line to my air governor has two feeds from it to various things in the engine bay - air cylinders, the clutch assist cylinder, the whole shutter-stat system, the air switch for the alternator field coil, and some other systems.  Now I understood that the D2 reservoir line was connected to the wet tank.  Is that actually so, or is it connected to the dry tank?  My air schematic doesn't show those lines.  I need to think about what it means for there to be so much stuff connected to the wet tank and what that means.

thanks, Brian

[bevans6]

I think I have answered my own question.  I found the MC9 manual that is on line and looked at it's far more complete air schematic.  It shows the reservoir line to the D2 governor to actually be connected downstream of the pressure protection valve.  So it is reading pressure basically in the accessory system, which makes no difference to normal governor operation but means that the various air users in the engine bay are schematically part of the accessory system as they should be.

This also raises big issues for troubleshooting.  Knowing that the governor reservoir sense line is connected past the air filter and the pressure protection valve could be very important if you were troubleshooting the operation of the governor.  I was taught in my air brake course that it was connected to the wet tank, obviously not so in this case.

Brian

[buswarrior]

Good on you Brian,

This reminds me again of the big problem with a driver's air brake courses and the instructors.

They rarely have greasy hands, having come from the driving ranks,

and as a group, have a really hard time saying "I don't know"

So they teach in absolutes and emphatically, to discourage questions.

Regurgitate the program material and sign the paperwork.

And we wonder why the professional driving population are the way they are...

A busnut, having to work on and trouble shoot the air system, as well as drive it, would find the additional training of a mechanic's air brake course beneficial. Trade schools and wherever your jurisdiction's truck and coach apprentice programs are run out of.

And, of course, Bendix.

happy coaching!
buswarrior

[bevans6]

And they have no clue about DD3 systems, and admit that at  least.  I put my my hand and said DD-3, he said I'v eheard of them and you are on your own, on the other hand you do need to know glad-hands and trailer brakes...