PD4106 park brakes won't release...

[buswarrior]

Hello.

At this point, the easiest and safest strategy would be jack it up, block the axle with your favorite collection of cribbing, remove the wheels, and then you get great access to your brake components.

The air leaks will be the biggest culprit in your functionality problem.

This little set back is simply catching up on routine maintenance, that was obviously ignored by the previous owner. Keep this in mind for the rest of the coach systems.

Since you have to carve into it anyway, as well as doing a rebuild to the chambers, I would suggest replacing all 6 lines to both chambers, replace the inversion valve, replace the supply line to the inversion valve, and replace the relay valve for the service brakes.

I expect you will find the relay valve leaking out the exhaust to some degree.

Carefully label all the lines you take off, feel free to cut them to get them out, and take the pieces to your local hose shop to use as patterns for new ones, note if you would like a little more or less length according to the hose routing you have now, versus the hose routing you would prefer. Also, life is a lot simpler if you consider get the two piece fittings at both ends of the hoses, and related hardware, makes it easier to selectively disassemble in the future. With one piece fittings, you have to wind the hose to install, easy to assemble new, bad if that is the end you have to remove later...

Be sure that the service brake hoses, from the relay valve, are of equal length. If someone has unwittingly fooled with the mounting location, brake timing balance is affected by unequal length hoses.

In reassembling everything, consider that someone will have to disassemble it sometime off in the future and use the anti-seize product of your choice on all mating surfaces, particularly the mating surfaces between/under the two piece fittings, to defend against those fittings fusing together again into a mass of rusty mess.

Once done, you will enjoy MANY years of trouble free operation on the air side of the rear brakes.

These all may be charged against the preventive maintenance budget, as they are all consumable parts, meaning they simply need to be changed periodically for reliable service.

Also, there is supposed to be a rubber boot on the exposed ends of the pushrods, the failure of that chamber will be linked to the absence of the boot allowing crap in there.

This is a positive experience, you get to fix this at your leisure in the driveway, not on the side of the road, ruining a vacation.

happy coaching!
buswarrior

[wildbob24]

Billy,

There is no access panel over the axle on your 4196 unless someone has added one.  You pretty much need to jack the bus and remove the wheels to easily access the chambers.

Unlike spring brake chambers or Mini Max chambers, which can be caged with a bolt, DD3s do not have this function.
Chris's suggestion of backing off the slack adjuster might work if there isn't too much tension on it. If there is too much tension, you should be able to loosen the mounting nuts a little to relieve some of it.

Another possibility would be to remove the hose at the lock port and apply shop air to the port and see if they'll release.

Bob

[bwze]

Again, thanks buswarrior and wildbob24. I'll be jacking her up and blocking the axle in the next few days. I've got an email into Luke at US Coach for some info on the rebuild kits for the DD3's....I'm assuming he could also help me with the inversion valve and relay valve for the rear. It is a little intimidating, but I'm sorta stoked to get to it so I can my investment rolling again. I'll be sure to keep this post updated and I may even start a new post to explain my DD3 adventure step for step....seems like it may be informative for others in addition to myself.....

[gmbusguy1]

Billy, all 4106's have a access panel inside the bus. walk to the rear where the far rear seat was the aluminum structure is still there but in the rv conversion build it may be covered up with plywood. it located right in the center of the bus and is about 30 inches long and maybe 10 inches front to rear. also you can see it from the outside. open the transmission door then look up in the center of the bus and you will see the aluminum panel.

it is normally used to get to the stater, exhaust manifold, and valve cover

make sure when you remove and replace it that it is sealed well so no exhaust gas can enter the bus

Luke will have all the items you need and the best part when doing business with US Coach is the FREE advice

Chris

[Barn Owl]

Billy,

Not much to add here because everyone has given you what you need and most have more bus wisdom than I have. Owning an old bus conversion or any RV for that matter is a lot of work, but after you get a few trips in it I think you will find that your reservations will fade away, and you have a very nice looking 4106 that will be fun to show off. As you have been getting acquainted with the underside of your bus are you cribbing or blocking it up? I hope you are doing it, others have touched on it but I haven't seen you mention it in your post that you have been, but you did mention that you will block the axle in the next few days. With new bus owners I like see in their postings that they are. Some of us who have been at this for some time take it for granted that everyone knows that they should never get under a bus that uses air bags without it being block up. If you have been blocking it as you have gotten under it great! I just wanted to make sure this was mentioned just in case, or for future owners who will be using the search function.

[zubzub]

I'll add to Barnowl's post and say, don't get under a bus that is on jack, or jack stands unless it is a huge trolley jack or something.  A bus will easily fall off jack stands/bottle jacks.  If I need to remove a wheel I use wooden cribbing to support the body/axle where I am working.   Mostly I leave the wheels on, jack the bus up and put blocking under the wheels, or drive the bus up onto blocking.  Also chock you wheels, all of them.  If these huge beast start to move at all, they keep moving....safety first...I'm pretty sure no  one wants to be squished to death by a giant polished turd.

[bwze]

Just to let everyone know, I have been jacking it up and cribbing before I get under it, but that does bring a good question to mind. Is it an acceptable practice to block up the shell also. Since my research indicated that the 4106 has a monocoque exterior, is it OK to also block it (the shell) near the wheels to offer additional support for changing, say, an air bag or whatnot.....this would be of course in addition to blocking the axle.

[luvrbus]

? for the GM folks does he have room for spring brakes I have saw them on GM buses but never looked close if so why even worry with dd3 you can buy new spring brakes cans for both sides cheaper than you can buy a diaphragm for 1 dd3 can


good luck

[Barn Owl]

Is it an acceptable practice to block up the shell also?

That is exactly what you need to do. The problem is that if you lost air to the airbags the "shell" drops to just a few inches from the ground squishing anything under it. Placing blocks between the axle stops and the chassis or under the strong bulk head mounts would prevent death if you lost air. I will also place cribbing at the side where ever I am working, and I use it until I get the blocks on the axle. I do not let the bus shell settle onto the cribbing because the shell itself is not able to take that kind of stress in one spot. It it just there to save my life if things go bad. Better to damage the bus than me!

[Ed Hackenbruch]

We were gone for a few days and i just read this topic for the first time. I noticed that the temps were low, 24 degrees?  Could it just be that the shoes have frozen to the drums and once it warms up they will release?

[bwze]

Pretty sure the brake shoes aren't stuck to the drum. I've got air pouring out of the back of the brake chamber where the pushrod exits when I push in the park brake valve. I'm thinking an o-ring or a seal has gone bad.

[bwze]

Just an update....got a call from Luke today with US Coach......what a great guy. He helped me with an exploded view of my DD-3 brake chambers and seems to be a wealth of knowledge otherwise. So glad he called today....pulled me right out of the ditch.......I'm planning on starting my DD-3 removal tomorrow and will attempt to keep a good record of my steps to help those who follow. So glad to be a member of this forum and thanks to everyone for your help.....

[Nellie Wilson]

Billy -

Sure hope you post photos of your progress. A friend of mine - a fellow busnut - offered me some used DD3s (which I gleefully accepted) so I'll also be rebuilding . He's bringing them to Arcadia, so I'll try to pick up some tips there too. I doubt these guys will let you go too wrong, but good luck on your project!

Nellie Wilson

[NJT5047]

Someone may have already brought this up, but the bus has specific jack points that should be used to safely lift the coach.  
A GM service manual will have this information listed.   Don't crib any body part.  
Unless you are working on known good concrete, don't use jackstands.   Good crossties and plywood shims sawed up make nice cribs (watch for metal frags in old crossties).  
As has been pointed out, once the DD3s are slacked off, the bus will easily move (if the brake shoes or cams aren't stuck).   The shoe-stuck thing can be eliminated by slacking off the adjusters.  The drive wheels should move freely.  An air leak from both pots indicate a valve issue...one pot leaking when the service brakes are applied could be a bad service diaphragm...and a bad enough SD leak would likely result in locked park brakes on the leaking side.    
Make sure that all of the air is exhausted from the park brake and service system before removing air lines.  
IF you're sure that the brakes are DD3s, you can rebuild them without worrying about the "big spring."  There's a spring inside, but it can be safely controlled as long as you are aware that it's in there.  
Here's a link that describes what's inside the cans and their function.  
http://www.bendixvrc.com/itemDisplay.asp?documentID=2393  
Kits to rebuild the units are available.  
The chamber may not be your problem...although sound like it is.  
Check the condition of your brake flex hoses while you're at it.  Most hoses have an abrasion cover that's gotta be moved in order to see the hoses.  If the possibility of mixing the hoses exists, mark them before removing them.  
If you get into the R8 (or R12) valve, take pictures of that puppie before pulling the lines.  
Get ready to work...60* for the coming weekend!  
Probably be about 80* in Ardacia.....and I'm staring at white!  Bummer!  
JR

 

[Busted Knuckle]

Billy,
Hopefully Luke, Clifford, Bus Warrior, or somebody can refress my memory on this. But if I remember correctly (been a long time since I worked on DD3's as our Setras use a different system.
But I seem to recall that air leaking out of one chamber means that it is leaking from the other side and not the air lose is from the hose connecting them together.
(I maybe off in this but seems to me I remember something like this and I hope one of Guru's/Yoda's can enlighten you and me on this!)
 BK