| Author | Message | ||
| Grant Thiessen (Busshawg)
Registered Member Username: Busshawg Post Number: 171 Registered: 10-2007 Posted From: 206.45.93.160  Rating: N/A |
My parking break is leaking air when the parking brake is applied. It's good when released. I beleive the valve is shot as when I turn it I can get it to slow down. MCI wants 352 dollars. Just wondering if ther is another source where I can save some bucks. I have tried new o-rings and it helped but sure didn't fix the problem. Another option I was thinking of but am unfamiliar with the idea. Has anyone ever replaced this valve with a standard truck valve? If so which line do I plug or cross over. Grant | ||
| marvin pack (Gomer)
Registered Member Username: Gomer Post Number: 490 Registered: 3-2007 Posted From: 71.55.197.237  Rating: N/A |
grant; go to a truck suppliers [parts] and they usually have cross-overs to match for a whole lot less money, If you can get any numbers take them with you. gomer | ||
| Luvrbus (Luvrbus)
Registered Member Username: Luvrbus Post Number: 701 Registered: 8-2006 Posted From: 74.33.63.151 Rating: N/A |
Check Eastern Marine they sell that valve for the DD3 brakes for 169 dollars good luck | ||
| larry currier (Larryc)
Registered Member Username: Larryc Post Number: 225 Registered: 2-2007 Posted From: 205.188.116.203 Rating: N/A |
Grant, I don't know anthing about MCI's but it sounds to me like you may need a quick release valve. Do you have maxi cans? If you do they need to release the air to allow the springs to set, thats the QR valves job. If its bad or sticking it sets up the senario you describe. It also does not allow the park brake to set until the air escapes, so don't just jump out and walk off because your coach may roll off without you. Look on Bendix's site for a picture of the QR valve series and see if you can locate the bad one on your bus. I have had a lot of luck with air brake alcohol unsticking these valves, if you can get about a quart into the wet tank and allow it to work through the system for a bunch of park set reppitions, the problem may go away forever. | ||
| Grant Thiessen (Busshawg)
Registered Member Username: Busshawg Post Number: 172 Registered: 10-2007 Posted From: 206.45.93.160 Rating: N/A |
Thanks guys I was thinking there may be a fault like that. However what threw me off was when I turned the knob. There is one position where it quits. Therefore I thought it must be the valve. The original o-rings weren't actually o-rings but square rings. I replaced with o-rings and it feels tight but still leaks. To add the alcohol would I just split the line on the output side of the dryer and add it? | ||
| FloridaCliff (Floridacracker)
Registered Member Username: Floridacracker Post Number: 402 Registered: 7-2004 Posted From: 65.33.22.197 Rating: N/A |
I found a new takeout on eBay for 10.00 There out there..... | ||
| Nellie Wilson (Vivianellie)
Registered Member Username: Vivianellie Post Number: 236 Registered: 11-2008 Posted From: 4.248.58.127  Rating: N/A |
Whoa, Nellie! (sez Nellie)  Grant: You say "My parking break is leaking air when the parking brake is applied. It's good when released." I'm lost (per usual, as you all know). My park brake has the OPPOSITE problem: It's fine when applied but leaks when released. Well, more than leaks... more like jet wash forced through a straw. My friend Ralph thinks it's probably a bad QR valve. But if that's the case, how could our opposite problems be caused by the same defect? (So far as I know, the brake systems on our buses are identical). My understanding echoes Larry's: When there's no (or low) air pressure, the park brake comes on. When you push DOWN on the knob, you're applying air which, in turn, releases the brakes. I can get mine to release by building to 125-130 psi and then REALLY smacking! that knob down. But it pisses air and, pretty quick, the park brake engages again. And using the auxiliary air chuck results in the same problem. But what I'm trying to figure out is this: If zero air ENGAGES the brakes, how can your's leak when they're APPLIED? I mean, what's to leak? There's (supposedly) no air pressure, right? Or is this QR thingy a two-way valve? It can stick open (when supplying air) or closed (when blocking air)? Makes no sense to me, but maybe that's it? (Just wondering out loud) Sorry, Grant - didn't mean to sidetrack your thread, but maybe we're on opposite ends of the same problem? You can't whoa, and I can't git! And, Grant, one last question: what do you mean when you talk about "turning" the knob? Do you mean the parking brake knob? Am I missing something here? Mine just goes up or down (I think) - I never tried turning the thing. Anyhoo, I'm going to do one of two things: Either tear the thing apart - if I can get the #@&**% spare wheel out - and find the problem or (opinions welcome) I'm going to bypass the *&^^% valve and fly without a parking brake for long enough to get to a mechanic. But, hey, at least I'll be warm! Luv Ya All (see, I'm already talking southern) Nellie Wilson | ||
| Jack Conrad (Jackconrad)
Registered Member Username: Jackconrad Post Number: 1106 Registered: 12-2000 Posted From: 71.3.157.139  Rating: |
If you have DD3 parking brakes, they use air to set the parking brake and also use air (in a different circuit) to release the brakes. Jack | ||
| Buswarrior (Buswarrior)
Registered Member Username: Buswarrior Post Number: 1619 Registered: 12-2000 Posted From: 76.68.120.67  Rating: |
There are many DD3 articles in the archives, use the search function and keyword "DD3" or my name under author, I guess, since I end up into them most of the time. When dealing with a DD3 system on an MCI, and the fewer GM or Eagles that came equipped with them, if you know something about spring parking brakes, best to forget everything you think you know and start reading again. There might be a part or two similar, they keep the coach from rolling away, after that, consider everything in their function to have no relation to spring brakes. For any air system problem, when you get air leaks from a device that at some point in its intended operation exhausts air, you must diagnose the system, the problem may not be with the part that is making noise. Spend some free time trouble shooting, or spend your ca$h replacing the wrong parts... happy coaching! buswarrior | ||
| Buswarrior (Buswarrior)
Registered Member Username: Buswarrior Post Number: 1620 Registered: 12-2000 Posted From: 76.68.120.67 Rating: N/A |
Oops, and Grant, don't pay MCI all that ca$h for a parking valve, there are cheaper options, if we're talking about the same parts. happy coaching! buswarrior | ||
| Grant Thiessen (Busshawg)
Registered Member Username: Busshawg Post Number: 174 Registered: 10-2007 Posted From: 206.45.93.160 Rating: N/A |
Hey Nellie, I'm no expert but it does sound like a bad brake pod, or at least I don't think it's your parking brake valve. Thanks BW, I won't pay them the cash, just way too much for a parking brake valve. The valve I pull to apply my brakes. Will probably leave it for the time being, as it doesn't leak when it is released and the system hold very well when released and when I hold the brake peddle down. We are considering coming you way in the next month or so. Not set in stone yet but if we do I'll probably look you up if that's alright. | ||
| larry currier (Larryc)
Registered Member Username: Larryc Post Number: 226 Registered: 2-2007 Posted From: 205.188.116.203 Rating: N/A |
Nellie, Your situation sounds like a blown diaphram on the emergency side. I know nothing about MCI or DD3 air cans but.... So if you push the park brake off with spring brakes then you are sending air to the diaphram to act against the spring and pull it off so you can drive. If the rubber diaphram has a hole in it then the air escapes and the air tank drains. There is also another aspect at work here that you should keep in mind. Since the air is escaping it is possible to drive with the compressor holding off the other brake and "partially" holding off the brake with the blown diaphram. The brake with the blown diaphram will will allow that set of shoes to drag and the brake drum will turn cherry red. Once that happens its real hard to keep your bus from burning to the ground. I would pull on a pit and block the wheels and use an outside air supply to trouble shoot the piggybacks. I would repair the one that is leaking immediately. If there is no leak in the piggybacks then I would find where the leak is and repair it. Grant, Think you can get to the bottom of what valve it is by releasing the brakes as in moving the bus, then set the brakes, If you immediately try to move the bus and it moves then the QR is not allowing the air to escape and the brakes to set up. You could also roll the bus, set the brake and see how far it rolls before the brakes set up. They should set immediately. If they don't I would replace the QR valve, they are common and cheap. | ||
| john w. roan (Chessie4905)
Registered Member Username: Chessie4905 Post Number: 1486 Registered: 10-2003 Posted From: 71.58.110.9  Rating: N/A |
See if you can down load the Bendix Air brake manual. It explains how all the air brake components work and how to service each. Many of the individual components are economical and easy to rebuild. Some can be done while still connected. The air brake treadle uses a replaceable cartridge for example. Some get intimidated by all the air lines connected to the item. | ||
| David Lower (Dave_l)
Registered Member Username: Dave_l Post Number: 155 Registered: 11-2007 Posted From: 67.58.201.132  Rating: N/A |
Grant I don't know if your is the same or not but on my MC7 there is a jar inside the curb side engine door it is mouted that when I open the door it is to the right. you just have to unscrew the jar put alcohol in it and screw it back on the air system draws the alcohol in. Dave L | ||
| Buswarrior (Buswarrior)
Registered Member Username: Buswarrior Post Number: 1623 Registered: 12-2000 Posted From: 76.68.122.95 Rating: N/A |
Hello. Air brake alcohol is not a lubricant, it acts as a solvent. It might be better to crack open the line ahead of the offending part and put some air tool oil into the line. As for the helpful posts above on DD3 systems...smarty pants comment to follow: You might as well read the latest dessert recipe for cantaloupe in Woman's Day magazine to fix your DD3 brakes, as read spring brake materials. They have nothing but confusion in common... Ok, I hope you will forgive that....we'll now return to regular programming: The short story: Full name: Double Diaphragm Three Airline Safety Actuator A DD3 chamber has 3 airlines attached to it. A DD3 parking brake is air applied. A DD3 service brake is air applied. There is no dangerous power spring in a DD3 chamber. A DD3 chamber has a locking mechanism that is spring applied and air released, to hold the pushrod in the extended position when the air leaks away. A DD3 system has an inversion valve, with 6 airlines and an exhaust plumbed to it. A DD3 system has two isolated supplies of air, one for service, one for parking... DD3's span from a time before there were/concurrent with, the arrival of spring brakes. Give or take 1960, nobody of the grizzled veteran set are quite sure of the timing, anyway, it was a time of lots of emerging technology, manufacturers and little standardization. Coach systems of the day were relying on a single source of air for everything, and a driveshaft mounted handbrake for parking... hence the "safety actuator" name, they introduced a powerful parking/emergency stopping option and a redundancy to air systems that would be regulated some decade and a half after their introduction... And spanning on to the post FMVSS 121, post 1975, systems, where there is a shuttle valve which allows an air failure in one to be compensated automatically via the brake pedal for the other. DD3 systems built to the modern design would be completely compliant today, except MCI finally relented to market pressures and changed to spring brake systems a few years ago now, as the supply and demand for DD3 brake chambers make them VERY expensive in relation to spring brake chambers. Sample costs last I checked: Spring brake chambers may be had for $75 each, a re-built DD3 with a core trade is $480. You're going to make me type it all out again....? There's lots of typing in the archives on DD3....really.....please? happy coaching! buswarrior | ||
| David Lower (Dave_l)
Registered Member Username: Dave_l Post Number: 156 Registered: 11-2007 Posted From: 67.58.201.132 Rating: N/A |
BW I was just answering his question, as it was sugested above and Grant asked where to add it. Dave | ||
| marvin pack (Gomer)
Registered Member Username: Gomer Post Number: 492 Registered: 3-2007 Posted From: 71.55.197.237 Rating: N/A |
On my MCI-8 the jar on mine under the driver is for my windshield washer. I don't know of anyother on the coach however, that won't be my problem if any because I SOLD IT TODAY YES Now I can go to McDonalds and get a burger with fries and a large drink. They were happy to find a coach in the condition of this one and said they looked for 2 years for one like this. Fired right up drove her down the road cleared it throat and put her in high gear and tops out at 82 according to the speedometer. Thanks for all the info I have ask about concerning it. gomer | ||
| larry currier (Larryc)
Registered Member Username: Larryc Post Number: 228 Registered: 2-2007 Posted From: 205.188.116.203 Rating: N/A |
Grant, I'm surprised that MCI was still using DD3's as late as 1984, but since BW also has a MCI, I guess it must. Hope you get it sorted out. If it is a DD3 chamber problem, look around, my rebuilder in Tacoma did my old bus DD3's for $105 each not to many years ago, but I do buy alot of brake parts from them for my business. If you go that route, mark the caps because they have to be clocked right for the air lines. | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 851 Registered: 8-2006 Posted From: 64.55.111.6 Rating: N/A |
Jack and BW have it exactly right! The way I read this, Grant's leak is in the knob, Nellie's leak is under the bus. BW has really outdone himself, and all I am going to do is to try and make it a little simpler. DD3s have air pressure to the knob when there is air in the park/emerg reservoir. With the knob depressed, air is released from one line, and applied to another, so depending on which o-ring is leaking, air will leak either applied or released. The knob essentially tells the inversion valve whether to apply or release. Nellie has either a bad inversion valve, a blown hose or something broken in the locking mechanism. In the release position of the knob and inversion valve, the lock mech line is CHARGED, and the park diaphragm air is RELEASED. Pop the knob, and the pressure reverses, diaphragm charged, locking mech released. The locking mechanism mechanically holds the application made by the diaphragm(s) after the air leaks off. NO QR Valve on DD3s, period. Nellie needs to go under with it released and blowing, it will be easy to find, no soap needed. Just remember NOT to go under an aired up bus without blocking it, being in a pit, or ? Don't get between the tires and the wheel wells when up either! G | ||
| Nellie Wilson (Vivianellie)
Registered Member Username: Vivianellie Post Number: 240 Registered: 11-2008 Posted From: 4.248.50.63 Rating: N/A |
I LOVE you guys all over again - That caution from Larry surely captured my attention: "The brake with the blown diaphram will allow that set of shoes to drag and the brake drum will turn cherry red. Once that happens its REAL HARD to keep your bus from BURNING TO THE GROUND." BW, JACK, GEORGE and all the others: THANKS! I'm printing this and taking it with me to fix the bus. I haven't learned much over the last couple years, but I've learned at least these three things: 1) It ain't rocket science - given time (and decent weather) most of this stuff is pretty straight forward... find the problem and fix it. 2) Leaking air makes noise, and noise is pretty easy to pinpoint, and 3) No matter how much work I (and others) do, it's still what it is... just an OLD bus. BUT, as several of you have told me, don't despair - beecause once it's fixed, it's fixed for a very long time. And you know what? Even if we're going down the road in lurches and short leaps - from one problem to the next - I'm living in the old girl and I love her to death. And, frankly, none of her problems stemmed from abuse or too many miles, but just from sitting in sub-zero conditions for way too long. Heck fire, I'd be grouchy too. Nellie Wilson PS. Hey, Jack C... you got my last message, right? I'll be there... and honored to do so. Thanks again! | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 853 Registered: 8-2006 Posted From: 64.55.111.6 Rating: N/A |
Nellie, 1. Read BW's long post again. 2. Then read Larry's second sentence again. 3. His advice on blown diaphragms only applies to Spring/Maxi type brakes, NOT TO DD3s, which both of our buses are equipped with. 4. We need to dispell another "old wive's tale," which you have already started to do with your post: "The air goes down and the emergency brakes apply." Both spring and DD3 type emergency brakes will make an emergency application when the pressure falls to about 60 psi. So, either there is enough pressure in spring brakes, which we don't have, to keep the shoes released, or the leak is so big that he can't keep pressure up, and gets a low air warning, followed closely by an emergency application! "Old Girl?" heck she's younger than me, watch your mouth! George | ||
| Nellie Wilson (Vivianellie)
Registered Member Username: Vivianellie Post Number: 241 Registered: 11-2008 Posted From: 4.248.37.122 Rating: N/A |
Well said, George! Sorry about that "old girl" crack though... she still has a cute little wiggle, especially when one shoe is spinning helplessly in the snow (something I hope never to see again). Nellie |
