Parking brake sticking on MC9

[ilyafish]

Hey guys!  Haha, one more silly question.

This has been happening since i got the bus, i just keep forgetting to ask....every now and then when i hit the parking brake, usually after parking the bus overnight or for a while, after i take the parking brake off, it sticks and i either have to put it on and take it off about 5 times before it finally goes, or pumping the brakes sometimes takes care of it too.

Was just wondering what this could be caused by

Thank you guys!

[gumpy]

After pushing in the button, you need to make a full application of the service brake to get the parking brake to release. Push the foot pedal to the floor, hold it for a couple seconds, and release it. That should allow the parking brake to release.

If that dosen't do it, you may need to have your brakes serviced. Might need grease.

craig

[ilyafish]

awesome!  sounds good to me....thank you so much :-))

[NJT5047]

Your bus has DD3 brake chambers on the drive axle. 
Unlike a truck with spring brakes, you cannot push off the park brake and drive off.
The DD3s have a ball locking mechanism that must push beyond the set pressure to release. 
Always air up the bus until the air compressor cuts out before trying to release the brakes.
They may release before max pressure is up, but they may not.
Be careful with hanging park brakes....that's a good way to burn your investment and PO your insurance company.
Drop the coach into drive or reverse and it should roll easily.  If not, verify which drive axle chamber isn't releasing.
As Craig sez, may need some grease.  May also need a chamber.   
Obviously, if properly releasing the park brake doesn't work, you gotta repair something. 
HTH, JR

[RJ]

To add to what the others have said thus far:

When getting ready to park the coach and set the parking brake, use a VERY light foot on the service brake - just barely enough to keep the coach from rolling - then pull the button.

This will avoid setting the mechanism so tight that it becomes difficult to release.

Do you know the complete air brake system check sequence before leaving the driveway?  If not, read this:

http://www.busnut.com/bbs/messages/12262/16203.html?1167072614

FWIW & HTH. . .

[Busted Knuckle]

Sounds like a visit with a knowledgeable bus nut is in order to give you a crashcourse in how not to destroy your coach before you actually discover the joys and mysteries of owning it! JMHO FWIW!  BK  

[jjrbus]

When you say the parking brake is hanging up. Are you saying the light on the dash is staying on or are you sure the brake is applied?  With my MCi the light would stay on while the brakes are actually released.  I remember fixing it, but cannot remember how.  Jim

[Kwajdiver]

Seems I recall, on a sticking brake, of going into reverse, touching the brake pedal.  Seems to set it free.

Bill

[buswarrior]

Settle down...

Sounds like his coach is behaving exactly as designed.

Good form suggests you give the brake pedal a good squeeze to the floor just after pushing in the parking brake control everytime with a DD3 parking brake, confirm it rolls free and away you go.

The longer story:

The DD3 system typically parks with an 85 lb air application, via a regulator, from the parking tank, which is at system pressure. You can't "see" the pressure in the parking tank via the dash gauge, it isn't plumbed that way, so it is blind to the driver.

The DD3 will release with only the control button being pushed in, if the pressure applied to the parking circuit and the brake chamber, has not decreased.

So, if you set the parking brake, and then release it, the bus typically will roll without a brake pedal application.

In order to get the locking rollers to bind, and require the brake pedal application to unbind them, the parking tank has to leak down from system pressure to below 85 lbs, or you had an awfully heavy foot on the brake pedal when you set the parking brake, creating the immediate drop in applied pressure, the slight easing back of the pushrod, and the roller bind, when you took your foot off the brake.

Keep in mind, the parking diaphragm is smaller than the service diaphragm, and the anti-compounding circuit won't let you make a parking application that is stronger than the 85 lbs setting, so the amount of brake pedal used when parking is irrelevant, it won't set until you release the brake pedal and the pressure drops below the 85 lbs. It won't let you bind it up stronger than the brake pedal can apply via the larger service diaphragm, unless something is broken/failed/burst/etc, in which case all bets are off anyway....

As noted in the earlier thread, if the parking brake does not release cleanly, every time, when using the good form method of release, you need to get the system diagnosed and repaired. A drive axle brake that is partially applied, even just touching, can be easily dragged by the engine without you noticing, and will heat up sufficiently to set fire to the tires, and then the bus.

There are many myths propagated regarding the sins and function of a DD3....

So, now what? 

Put foot on brake pedal, stop, pull the control knob and walk away. When leaving, push in the knob, squeeze and release the brake pedal to the floor, and then like every driver should, with every vehicle, no matter how equipped, but especially with our old, worn out, lot lounging, bus conversions, be sure it rolls freely before driving off.

happy coaching!
buswarrior

[Ncbob]

This in one of those problems which will make you want to tear your hair out exspecially when you're all loaded and ready to go. Absolutely I would follow the instructions of Buswarrior to the letter...he's our brake expert.

Before I replaced my rear brake actuators this problem drove be NUTS! My opinion was that the lube which lubricates the balls which hold the parking brakes was old and stiff (my bus is 40 years old).

It happens once in while still when we sit for a prolonged period. If they don't release on the first or second try..I re-apply the parking brake by lifting the button and wait for full pressure and start the sequence all over again. Invariably it's easier and productive the second time.

HTH

NCbob

[gumpy]

My opinion was that the lube which lubricates the balls ... was old and stiff...

It happens once in while still when we sit for a prolonged period.  ... Invariably it's easier and productive the second time.

HTH

NCbob

Ho yeah, Bob, that helped a LOT!!! 

[Nick Badame Refrig/ACC]

Way back when...I was green too!

I think the first 10 times I had to exit the Cape May Ferry, I couldn't figure out how to get the PB released.

Under presure, is the best time to feel like an idiot!

Nick-

[PP]

My opinion was that the lube which lubricates the balls ... was old and stiff...

It happens once in while still when we sit for a prolonged period.  ... Invariably it's easier and productive the second time.

HTH

NCbob

Ho yeah, Bob, that helped a LOT!!! 

I think Gumpy's (Craig) mind is in the gutter. JMO FWIW LOL

[NewbeeMC9]

I think he and bob are trying to hi jack this thread

going from "Won't Stop" to "Don't Stop"

[Ncbob]

I don't know about Gumpy...but I WAS talking about DD3 Parking Brakes.

Bob