Parking Brake - Air

[PowerstrokeNC]

I just want to make sure I understand he parking brake correctly on my M923-A1.
It is spring activated, so when you 'let off' the parking brake air pressure is applied and deactivates the brake. When you apply the parking brake the air pressure is released the spring mechanism takes over and applies the brake.
This is also a fail safe for loss of air pressure, because then parking brake automatically comes on. Did I figure this out correctly or am I way off base?

Thanks

 

[Flyingvan911]

If it's the same as spring brakes on 18 wheelers, then yes, you are right. Do you have to press a button to release the "parking brake"? If yes, then you are right about the brakes.

 

[bearboley]

Your correct. Same operation as a modern 18 wheeler but different style 18 wheelers have scam style breaks and you have wedge style breaks.

 

[tigger]

You are close . the parking break stays released till air is lost or it is reaplied, it does not operate your service brakes. there are 2 chambers 1 is for the parking break. the 2nd is for your servce brakes witch is operated by a seperate air diaphram. that operates the service brakes.

 

[jwaller]

you described it perfectly in your first post. all this other talk will just confuse the situation.

 

[tigger]

you described it perfectly in your first post. all this other talk will just confuse the situation.

He is not correct the parking break spring does not operate the service brakes!

 

[rawhide]

I didn't see where the OP said anything about service brakes in the first post. Air bleed off, whether by switch or by accident, enables the parking brake. Applying air pressure releases the parking brake.

 

[tigger]

my mistake i read it incorectly! he is correct

 

[PowerstrokeNC]

Thanks for all the input guys, I am new to air brakes and so want to make sure I have this right.

 

[doghead]

Understanding your air brakes is one reason why a CDL is typically needed with air brakes.

 

[emmado22]

Whats the -10 have to say about this?

 

[raeme]

Don't forget to put a quick realese in the system.
raeme.

 

[Bighurt]

Also keep in mind they are seperate on the 939 series, it doesn't use dual chambered units.

 

[M35A2-AZ]

Ok, I have to ask, on the M923a1, what is the correct way to park the truck?

1. put the parking brake up
2. push the spring brake button in to park.

Thanks!

 

[jwaller]

Ok, I have to ask, on the M923a1, what is the correct way to park the truck?

1. put the parking brake up
2. push the spring brake button in to park.

Thanks!

nope. put the parking brake up. thats all.

do not push in the spring brake over ride unless you have a problem with the truck and it must be moved.

 

[jwaller]

Also keep in mind they are seperate on the 939 series, it doesn't use dual chambered units.

this is true for the front, but the back are dual units. that is where you get your parking brake from.

 

[Bighurt]

this is true for the front, but the back are dual units. that is where you get your parking brake from.

Forgive me I'm still learning the M939 series and was confusing primary and secondary brake systems. However I'm fairly certain the primary system only has a service chamber.

Feel free to correct me as this is how I read the TM and whats under my truck