Green needle

[Jim Blackwood]

I realize I could just look this up, but what fun is that? So the air pressure gage has a red and a green needle. Which system is the green one for again?

The red one stays up for days but the green one bleeds off. Following advice on here I ordered a bottle of leak check and thought I might look around a bit.

Jim

[buswarrior]

Provided they are not cross connected...

Green is down the back/primary, red is up the front/secondary.

Old titles, primary/secondary, they are both important and mission critical.

Happy coaching!
Buswarrior

[Jim Blackwood]

Thanks BW. Which one gets air first, the green needle? I've forgotten.

But it sounds like I need to look first at the tanks and valves in the back, is that right?

Jim

[buswarrior]

Both get the air at same time, there is no priority between the two brake service tanks, they are equal, and protected on the incoming end by one way check valves.

Check your air schematics to see which other things come off the green needle tank, they are just as likely suspect as the rear brakes.

Happy coaching!
Buswarrior

[Jim Blackwood]

Yeah, I'd do that but the schematics in my service manual have all been cut off short so you can't see how one page connects to the next. So there's no way to trace the lines out. The wiring is the same way.

It is an online download from MCI, so I really don't see how anybody has been able to use those.

Jim

[chessie4905]

my GMC manual has a fold out of brake system. Lines are too small to easily trace. Had my sil enlarge them 400%. She had a very large printer where she worked,.Did same with wiring diagrams. Easy to work with now

[Jim Blackwood]

Wish I had that option.