Parking Brake Canister Question

[Glennman]

So the parking brake canisters on my '74 MC-8 do not have a hole in them to receive a cage bolt on the back side for pulling the spring. Does that mean I need to replace the entire canister? I believe I have a leaking diaphragm in one of them. Thanks for your help everyone.

[buswarrior]

You have DD3 brake chambers, not spring brakes.

No big spring, no caging bolt, and bunch of other things that render spring brake system knowledge useless and sometimes dangerous.

The home handyman busnut can safely change diaphragms in a DD3.

Happy coaching!
Buswarrior

[Raymond smith]

3 hoses going to it = DD3
2 hoses = spring brakes

[Glennman]

So, it appears from some previous posts on this board, and from pictures I found on Google, there are only smaller springs inside, and not the large "death spring". I take it that with the DD3 system, when the brake pedal is applied, the air pushes the rod that pushes the pads, then when you activate the air brake button (to lock the brakes), that locks the mechanical DD3 in place. This would be in lieu of the spring (with spring brakes) that would rely on the air being released allowing the spring to lock the brakes instead. Is that a fair assessment?

Is this why with the DD3, you have to apply the brakes, then activate the air brake button in order to cause them to lock? Or, is that the procedure for all air brakes (?)

[buswarrior]

Dd3, double diaphragm

Service and parking are both air applied.

The locking rollers are to hold the rod, if the parking air leaks away while parked.

Happy coaching!
Buswarrior

[Glennman]

Thank you buswarrior (and others)! That answers my questions for now. Much appreciated.