[Gerald]

I was curious about #55 the double shuttle check valve, air inters from brake pedal assembly via primary tank to the tree for Primary and the secondary systems gets air from the secondary tank, them from double shuttle goes to E-brake and R-14 valve in rear. What does it do between Primary and secondary systems?? If double shuttle is bad what affect will it have. Just when I think I understand the system then looking at air schematics I’m confused , Also from (front) system secondary pushing brake pedal applies air pressure to front brakes and to control port on#52 spring brake valve assembly, So front system (Secondary) has something to do with spring brakes?

[Greg]

Here’s a link:

DC-4 Link

Here’s a link to the “Brake” section of the Prevost mx manual:

Brakes link

[Corey]

And just when I thought I understood ….it now look like I was originally told that there are two separate systems ( primary and secondary) and if I’m reading schematic right there is a junction at the Tee ?

[Eric]

That is where they both come together to feed the parking brake release, however they do not feed each other and do not cross connect, so to say.

[joel]

Gran, The thing to remember is if you get a low pressure situation your parking brakes are going to be applied when you do not have sufficient pressure to the parking brake.

Any low pressure alarm is cause to get to a safe spot quickly because you are about to lose control over the brakes.

An accessory system loss of air is going to cause a drop of total brake system air pressure until it drops to the protection valve pressure which is going to be sufficient to keep the parking brake off and to provide coach brakes.

Until and unless you know what is happening and why, get to a safe spot.

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1999 XLV X-6872,  liberty #440