I've reached another cross road and don't know what direction to take. I've used the search button and have found multiple entries on park brakes that won't release, but none that seem to correspond to a 4106. When I bought this bus the other day, we had some trouble getting the park brake to release, but it eventually did. The guy I bought it from really didn't use it at all......he may have put 5 or 600 miles on it in 10 years. I'm pretty sure that these park brakes aren't original since the the GM manual refers to hand brakes. This being said, I'm not sure if I have DD3 or spring brakes. I've tried several time to get them to release. I'm using my air compressor in the garage (helps recover the pressure quicker) along with the on-board compressor to build to the max, then dumping the park brake valve and then applying a 10 to 20 second service brake to get it to unlock, but then trying to put her in reverse keeps yielding a stuck park brake. It I hold the service brake pedal down too long the park brake valve pops back up. Anyone got any pointers?
If no one has changed the brakes you have ICC brakes bleed all the air off they should release,those are called chaser brakes air pressure leaks off you chase the bus down the road that was the reason for the hand brake,what is written on the park valve
good luck
try holding foot brake before and during parking brake release.
Luvrbus, the park brake valve is just a standard valve (I guess).....pull to set, push to release. Is there anyway to tell what type brakes I have?
Bob, I'll give your recommendation a try first thing tomorrow.
prob biggest problem with your bus is lack of use. Air relays and ck valves become dry and tend to stick or bind from lack of use. Back feeding with shop air sometimes will release a stuck valve or relay. Again feeding with both sources at the same time can confuse a relay or valve including ck valves or you air compressor governor. Experiment with different combos. make sure your brake cams/shafts are greased and not binding. Just a few things to look for on a bus that hasn't been used much.
Billy,
The only way to determine which brake chambers you have(If the PO can't tell you) is to look.
You could have Mini Max chambers, or DD3s, or spring brakes.
The Mini Max chambers were often used on the 4106 because they could be installed without modifying the mounting bracket. They are easily identified because the relatively short chamber is made from cast aluminum. They will have 3 hoses attached.
DD3s and spring brake chambers are larger and made from steel. The mounting bracket has to be cut and relocated for these to be installed. They are different in appearance, but the easiest way to tell the difference is the DD3 will have 3 hoses attached, while the spring brake will only have 2 hoses attached.
Bob
Billy -
WAIT!
Before you try what Robert suggested, take a look at your rear brake cans. There are two different types of parking brakes used on buses, DD3 and Spring. Spring brakes were not an option on 4106s, but DD3s became optional long about mid-year of 1963 production. A previous owner may have installed either type, so you need to determine what you've got, because the release procedure is different between the two types!
How can you tell what you've got?
Simple - look at the rear brake cans. How many air lines do you have coming off the cans - 2 or 3?
If two, you have spring brakes.
If three, you have DD3s.
Release Procedure - Spring Brakes
1. Build coach air pressure up to governor cut-out (approx 120 psi).
2. Lightly cover service brake with foot - do not apply, just cover.
3. Push in on parking brake knob until it seats. Wait 3 -5 seconds.
4. Put coach in gear and away you should go.
Coach should roll after #3. If not, then pull knob back out to reset brakes and repeat steps 1 - 3. If coach still doesn't roll when put in gear, something is wrong and needs to be looked at. Make sure coach wheels are properly chocked, preferably front and rear, before doing any investigative work.
Release Procedure - DD3 Brakes
1. Build coach air pressure to governor cut-out (approx. 120 psi).
2. Lightly cover brake pedal - do not apply, simply cover.
3. Push in parking brake knob to release parking brakes.
4. AFTER pushing in knob, apply a FULL service brake application (FLOOR IT) and hold for 3 - 5 seconds.
5. Release service brakes, coach should roll when put into gear.
6. If coach doesn't roll, lightly cover service brake again (do NOT apply - just a light touch).
7. Pull knob to reset parking brake.
8. Repeat steps 1 - 5.
As stated above with spring brakes, if the coach doesn't roll after steps 1 - 5 are repeated, there may be a problem that needs investigation.
Setting Spring Brakes for Parking
1. Once parked, lightly cover service brake sufficiently enough to just keep coach from rolling.
2. Pull parking brake knob to set brakes.
3. Release service brake - coach should not move.
4. If coach will move with parking brake set, have brakes looked at immediately!
Setting DD3 Brakes for Parking
Procedure is basically the same as for Spring Brakes, but the critical point here is that you LIGHTLY hold the coach with the service brakes before pulling the knob to set the parking brake. You should ONLY apply enough service brake to keep the coach from rolling, no more. The harder you have the service brakes applied, the more difficult it will be to release the DD3s.
FWIW & HTH. . .
;)
Was hoping a more experienced Gm guy would give correct procedure for your coach. I have tried many procedures when things are sticking hoping to get them to correct them selves.I didn't know the correct procedure before now Bob
Billy here comes another comment on brakes I have a 64 4106 and the flip switch is not a parking brake but a bad weather brake change it will not lock the braakes down. you have a hand pull brake between the drivers seat and left wall. Some times when not used much the break pads will stick in the drum. take a 2 or 3 lb. hammer and tap around the housing . also trying to put back presure on them.
Well it's 24 here in South Carolina....brrrrrr. I put on my coveralls made sure the wheels were chocked and squeezed underneath the bus to get a look at the brake cans....here they are...
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I'm assuming, by the reading RJ's very detailed post (thank you so much by the way), that I have the DD3's installed, or I could have the Mini Max chambers referred to by wildbob24. Not really sure.....If I do have the DD3's then I may have a problem. I may have already tried what robertglines1 suggested yesterday (applying service brakes while releasing park brake). If so, how hard is it going to be to get them to release now. Is there an alternate method of getting them to release if the proper procedure is not followed.
papatony, I don't have a flip switch or a hand brake between my driver's seat and the left wall....I can only assume that this was removed by the previous owner....
P.S. if you take a close look at the lower photo, the hose to the right is showing signs of damage to the outer hose covering, need to get that replaced..... ;) which brings up a good question....where can you get OEM replacement parts for these old coaches?
Billy,
Like RJ said, make sure you push in the knob before applying brakes. I have DD3s also, I had problems releasing parking brakes too until I started doing it the right way per RJ.
Brandon
Billy,
Those are definitely DD3s, so RJ's procedure should work for you.
It's possible the internal locking mechanisms are gummed up and cycling through RJ's procedure a few times will help free them up.
There is a zerk fitting on each chamber whose purpose is to periodically lube the lock mechanism (one or 2 squirts only; it's easy to use too much). If it hasn't been done in over 10 years, it may be time for a brake chamber overhaul.
OEM parts can be hard to come by. The most likely source is Luke at US Coach: 1-888-262-2434.
Bob
What is the air psi when the parking brake knob pops back out. Sounds like you may be loosing air and the brakes apply for safety That's what they do if there is not enough
Rick 74 MC-8
Rick, the valve pops back out at 90 psi....this happened because I was holding the foot brake down for like 20 secs (saw it on a post somewhere and was giving it a try) and the pressure dropped to what I guess is the low pressure pull in for the compressor.
wildbob24, where is the zerk on the the chamber....I felt all around...top, bottom, front, back....I see don't see any fitting on the chamber itself. There are two fittings back by the slack adjuster. I gave them a few squirts....but don't see any others...
Is it still OK to use external air to help build the pressure quicker, or should I only use the on-board air?
And is there a possibility that I've done something to make releasing the park brakes worse by not following the proper procedure....and if so, is there a way to remedy it?
wouldn't think you hurt anything by not using by the book procedure. I can assure you allot of drivers never new proper procedure. Just start and point. I apparently didn't and have been driving truck cranes and lowboys for 40yrs. buses for 15 now. I just shared what had worked for me when brakes wouldn't release. Normal operation I put foot on pedal lightly and release parking brake. If it sticks I stroke a couple times.Have never been past that. A brake problem caused the fire in the coach I'm rebuilding now. Parking brake valve is normally set to pop back out on low air around 60 lbs. some replacement valves set at 45 lbs. 90 is about where air compressor should cut back in.and off around 120. the grease zerts are on back of backing plate (brake)and lube the shafts that must move freely to release and apply brakes. Good luck Bob PS I learn something new ever day!
Bob some breaks won't release until about 90 PSI.
I have 2 buses that are that way a '95 Setra and '97 Dina both have to have between 90-100 psi to release the first time, but don't reset them selves until around 60-70.
DOT rules and the standard is 60 min. for the reset for lose of air pressure.
FWIW ;D BK ;D
BK ,I reread his post and he said the parking brake was popping back up at 90. Isn't that to high? shouldn't be around 60? Bob
Billy,
The zerk on the chamber should be next to the lock port, where the closest hose to the mounting bracket is attached.
In looking at your pictures, it appears that your chambers do not have them. Must be older versions.
Later installations(like my buff) had a mechanical release on the end of the shaft where it attaches to the slack adjuster.
If yours doesn't have these(and it probably does not), the only way I know to release them would be to unbolt the chambers from the brackets. You would need to have the bus jacked up and the wheels removed in order to safely do this.
PM me your email and I'll send you a couple of scanned pages from my manual with pictures of the zerk location and the mechanical release. The files are too large to attach here.
Bob
Bob in a perfect world yes. But there are variables that could effect it. Could be someone has changed out the release valve itself. Or any other valves in the system. Problem with these old coaches is if you don't have a knowledgeable mechanic and parts man working together sometimes the parts guy will tell you "this will work, it's the same thing only newer!"
It takes someone like Luke (and a few others) who knows the difference, and will take the time to find you the right part.
;D BK ;D
PS also his system could be gummed up.
Billy
With the coach aired up if you push in the parking brake knob doing nothing else will it hold psi or do you hear air leaking ? It should hold air might drop a little from charging the brake system but it should hold once that happens with no air escaping
Rick 74 MC-8
Quote from: robertglines1 on December 24, 2010, 08:16:17 AM
BK ,I reread his post and he said the parking brake was popping back up at 90. Isn't that to high? shouldn't be around 60? Bob
That is high. DOT requirements are that the warning alarm sounds at around 60psi and the emergency brakes apply at around 40psi The problem here is old DD3 systems are plumbed differently than modern spring brakes. Plus, we're dealing with a modified system that may or may not be correct.
In a typical DD3 system(like my Buffalo), the parking brake control is sensing the pressure in the parking brake reservoir, which is isolated from the rest of the system by a check valve. The pressure gauge reads from the accessory tank, so the 2 are not necessarily going to be in sync. So, the accessory tank pressure can drop to 0 and the parking brakes will not apply. The warning buzzer will come at about 60psi, though.
The fact that Billy is losing pressure while his foot is on the brake indicates a leak somewhere. My approach, at this point would be to get the bus up in the air and observe and search for the leak(s) while a helper operates the brakes.
I would also check and make sure that there is pressure at the lock port when the parking brake is released. The double check valve or the inversion valve could be stuck and preventing the proper flow of air.
Bob
Well here I go with another video....they say picture is worth a thousand words...well a video definitely trumps that....
GM PD4106 - Trying to release park brake..... (http://www.youtube.com/watch?v=VkLTAaPc1N0#ws)
I followed RJ's procedure to a tee quite a few times, but nada....I do hear air escaping while the park brake is depressed until it gets to around 90 psi and then the valve pops back up...
I got a feeling I bought myself a big ole polished up turd.... >:(
Billy,
I wouldn't discount it as a "big ole polished up turd" just yet!
Most likely it will be a simple fix.
But even if you have to replace both DD3's and a valve or 2 you will have a nice coach to enjoy for a long time to come!
;D BK ;D
just a old girl that needs a little tlc! soap and water time. or change parking brake valve .squirt a little soap water around it to see if it is leaking. Good luck. once she gets into a good mood you will be happy also.
Billy
Find out where the air is going when you release the brakes and you may have found the problem
Rick 74-MC-8
Billy,
Try not to get discouraged, it's not a turd! ;D I definitely know how you feel though. I have an older GMC as well, there have been times that I wanted to burn it to the ground, but once you get all this little stuff sorted out your gonna love it. It seemed like for awhile there every time I got in my bus I had to have something replaced or repaired, it can be very frustrating to say the least.
Hang in there. :)
Brandon
Just went out and pressurized the air system with my garage compressor again. Stepped inside and pushed the park brake valve down and then started my search for escaping air. Found it at the back of the driver's side rear brake chamber...right where the push rod leaves the chamber itself. With this new discovery, it seems I may become acquainted with a DD3 rebuild......for both sides..... :P
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I also checked for air leaks with the valve in the park position and found it leaking at this frayed hose that I noted earlier, so I guess I'll be replacing that also....
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Anybody got any suggestions on where to get a rebuild kit for these?
II was just writing up something to have you check for escaping air at the cans. I had a similar problem with DD3s (4905) which turned out to be a hole in the service brake diaphragm. The symptom was difficulty releasing the parking brake and air escaping from the DD3 unit while service brake is applied. Yours looks like a hose. Replace them all while your at it.
Your fortunate to have DD3s on a 4106 as many just have a simple system that can leave you with NO BRAKES if air pressure is
lost.
.
The DD3s do have an emergency disable mechanism where the rod connects to the arm. It completely disables rear brakes. I assume the fronts would still work but dont know for sure.
.
That would allow you to move the bus and perhaps get it on some ramps so you can work on it. I you have yet to put your bus on ramps and block it up ( this refers to blocks between axle/bump stop) that is a whole new discussion. Its safe when done right but extremely dangerous otherwise.
.
Tom P.
I also have a 4106 (1962). Mine only came with the hand brake for parking. The ICC will hold it fine, but I don't want to depend on it for any length of time do air pressure going down will have me chasing her down the road. I am looking into changing to the sprin brakes. They don't seem to be very expensive for brad new. Is it possible you also have the hand brake? That was stock on mine. It is a drum brake attached to the drive shaft. Just to be extra safe, I will keep both systems when I get done. (if ever)
Ed
Billy, most of the advice in this post is Great.
However YOU NEED a 4106 service manual and supplement as the DD3's are in there
safety first!!! your bus is heavy and NEVER go under it (not even for a minute) until it is properly blocked from falling and Killing you should you lose an airbag or line. this has happened and we have lost busnuts to this.
if you are not familiar with air brakes my advice is to get the bus to a qualified BUS technician these vehicles are heavy and the brakes need to work right
from the photos you posted and the leaks you can find if it were me I would replace both rear brake cans with rebuilt units from Luke at US Coach along with all new hoses to the cans
Merry Christmas
Chris
Fwiw Kirks Automotive in Detroit had a good buy on rebuilt DD3's a few months ago 313-933-7030
This has been a very interesting string to me because I just went from a 4104 with spring brakes to a 4107 with DD3s.
With the DD3 I found quickly that pushing in the park button Before pushing the foot brake works much better. I also find that most of the time the brakes release shortly after I push in the button and I don't need to use the foot brake. I do make sure the buss will roll easily when it does this though.
I don't use a lot of foot pressure to set them unless on a steep grade, then I give it a good push but not all the way.
All that being said, spring brakes are sure a lot simpler design and easier to operate!!
Quote from: luvrbus on December 24, 2010, 12:02:33 PM
Fwiw Kirks Automotive in Detroit had a good buy on rebuilt DD3's a few months ago 313-933-7030
I second Clifford on Kirk's as a good resource! I've never bought brake chambers from them, but I have bought starters and alternators from them @ good prices.
Also check with Luke @ US Coach 856-767-4848 he will have them also and probably a rebuild kit if you choose to go that route!
;D BK ;D
Great info guys....just got back from a Christmas Eve dinner with friends and had an opportunity to talk with a fellow bus owner. He's got a big garage and all the necessary jacks and blocking to help me when need be....sure is great to have connections. Another friend told me that I may be able to find rebuild kits for my DD-3's at a local shop here in Columbia..
Anyway, signing off for tonight.....hope you all have a very merry Christmas......and remember the reason for the season....
P.S. Here's a link to a PDF that a buddy of mine found with some really good info from Bendix on the DD-3 and the SD-3.....
http://www.bendixvrc.com/itemDisplay.asp?documentID=2393 (http://www.bendixvrc.com/itemDisplay.asp?documentID=2393)
Gus, I realize you are used to spring brakes of course so please do take my comments as trying to help you prevent a stuck or partially released brake can with the new to you DD3's.
I would follow RJ's advice in this post regarding setting and removing the brakes with DD3's it is very easy to just push in the parking brake valve and feel the coach roll thus driving away with out a full 3 to 5 second Full treadle application and have a brake can (the parking circuit) not completely disengaged
and as we all know bearing/axle problems and Fire are a very real possibility
just trying to avert a small disaster
Merry Christmas
Chris
Chris you are going to like the 30/36 spring brakes on your Eagle no more hassle with DD-3 hard to believe the Eagle has spring brakes since the 80's
good luck
I completely forgot to ask the board a most important question that I can seem to find the answer to.....how do you get a DD-3 to release is the diaphragm is bad.....seems like there would have to be a way to get it to release manually....anybody got any pointers? ???
Chris,
Thanks, I do that and is what I meant by my last sentence, first paragraph.
I wasn't clear about that though.
I saw the PO move the bus without using the foot pedal and saw firsthand that the brake wasn't completely released.
Please don't try to rebuild those things by your self they can be very dangerous!!!!!
Quote from: papatony on December 25, 2010, 09:49:33 PM
Please don't try to rebuild those things by your self they can be very dangerous!!!!!
Papatony,
While I appreciate your concern, rebuilding a DD3 is neither dangerous or difficult!
Spring brake cans on the other hand are very dangerous and so cheap it ain't worth rebuilding them!
;D BK ;D
That being said BK, how do you get one to release if stuck so that you can remove it for rebuilding?
Billy, just back off the slack adjuster, remove the airlines keeping track of which line goes where then remove the two nuts holding the can to the mount.
Chris
10-4....that was my logical conclusion, but didn't know if there was a special way to get the rollers to release the push rod back to it's unsprung position.....thanks
Does anyone know if there is an access panel above the rear axle in a 4106 that would allow easier access to the brake chambers and inversion valve?
Billy I wish I could help ya more but I know very little about GM coaches. But I really doubt it!
But jacking and blocking the bus, and removing the drives on one side will help!
;D BK ;D
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
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
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.....
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
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.
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. ;)
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.
? 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
QuoteIs 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!
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?
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.
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.....
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
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 (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
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!)
;D BK ;D
Not sure that I follow you there BK.
BK is having a generic warning bell ringing in his head, which shows there is still signs of life!
He expect he has triggered a distant memory that with DD3 you can get fooled into fixing the wrong part when you find air leaking someplace, when it is really an indicator of a leak elsewhere, feeding back via another sealed part of the system. Usually found flowing freely out an exhaust in a valve.
Doesn't sound like your problem right now.
happy coaching!
buswarrior
Go here -------------->http://www.busconversions.com/bbs/index.php?topic=18495.0 (http://www.busconversions.com/bbs/index.php?topic=18495.0) for a follow up to my DD-3 brake adventure.