| Author | Message | ||
| ChuckMC9 (Chucks)
Registered Member Username: Chucks Post Number: 1149 Registered: 10-2003 Posted From: 70.3.47.103 Rating: N/A |
Morning, Ghents - If you would be so kind as to double-check my understanding of the steps involved in changing out a DD3 on an MC9... Assuming I am blocked & chocked, these are the steps I think I need to follow this morning, and I'd like you help me be sure that I get what the book + Bendix is telling me, plus my micro-steps, is correct: Removal: 1) Clean crud from can mounts, slacks and anything in the vicinity of the surgery 1.5) Mark or make clear which line goes where 2) Air up to 90 or so (using aux compressor) 3) Release parking brake in usual way 4) Be sure it don't roll!  5) Drain wet, dry & park tanks 6) Take a deep breath 7) Disconnect service line at chamber 8) Disconnect park line at chamber, being prepared for air to escape 9) Go inside, engage park push/pull 10) Disconnect lock port line 11) Remove cotter, then main pin 12) Back off slack 13) Remove chamber mounting nuts 14) Pull that ol nasty thing outta there Reinstalling: - - Reverse the above more or less + teflon tape (keep away from ends of threads) - Adjust slacker - Send the board a big thumbs-up after I see that big beautiful dash gauge NOT move when I apply the brakes! - Return the old for core credit, buy one for the other side! -------------------------- It very well may seem ridiculous to you for me to ask you to check me on this for what many of you consider a trivial job, but I'd hate to get terminally squished on this fine day! If you have any comments, please let me know! I'll be under there cleaning for some time, so I'll check back before I start in earnest. Thanks a million! -c (Message edited by chucks on November 07, 2007) (Message edited by chucks on November 07, 2007) | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 287 Registered: 8-2006 Posted From: 207.231.75.253 Rating: N/A |
Chuck, Anyone who thinks a DD3 can replacement is "trivial," has never done one! A couple of thoughts, though: 1. While parking brake is applied, no pressure in the lock line, and the service line, pressure in the park line. 2. Parking brake released = pressure in the lock line only. 3. The inversion valve will trip and try to make an emergency application when the pressure falls somewhere in the 80's. So, when you go to drain tanks, an application will occur. 4. So, my suggestion would be to be absolutely be certain the bus is properly blocked up at the jacking points, do your cleaning and identification, and then get a release, and remove the pin between the yoke and the slack. Then remove the parking application line, which will be dead. The service line can come off at the same time, but the lock line will be charged. Watch for flying hoses when you either apply the parking brake, or the inversion valve does it for you while draining tanks! Good luck, just BLOCK IT WELL! George | ||
| ChuckMC9 (Chucks)
Registered Member Username: Chucks Post Number: 1150 Registered: 10-2003 Posted From: 70.3.47.103 Rating: N/A |
Disappointment sets in. Everything is all ready and all except the outside nut are wiggled enough to know that I can get them loose when the time comes. But I cannot get that outer nut budged with the wheels on. Drat. I was contorting every which way in that limited space but cannot budge it. I thought that with the pressure off the can so that it's not pulling against the nut might have helped, but not enough to get purchase in that space. OK, I'll find a tire guy. And update on completion! Many thanks, George, for some clarification of the 'toggle' effect between the park and the lock pressures. | ||
| Buswarrior (Buswarrior)
Registered Member Username: Buswarrior Post Number: 1105 Registered: 12-2000 Posted From: 76.66.19.38 Rating: N/A |
Hello C'9 Don't bother airing up, just block wheels, drain all tanks completely, and, as noted, remove clevis pin from slack adjuster/pushrod. Draining all the air, there will be none left to cause trouble as you take off the lines. You may find it helpful to remove the slack adjuster, if it continues to be in your way after backing it off. Yes, pulling the tires off makes it a whole lot easier to access, and I'd have added it to the set-up: block suspension points, jack up and block under axle and remove wheels. Consider replacing the airlines and the inversion valve, if you do not know its vintage. happy coaching! buswarrior | ||
| ChuckMC9 (Chucks)
Registered Member Username: Chucks Post Number: 1152 Registered: 10-2003 Posted From: 70.3.47.103 Rating: N/A |
Hey BW, I thought the slack adjuster/plunger would have to move freely - and to enable that, I thought it would have to have air applied to unlock. Hmmm. So the pin would have to be removed with all that pressure on the arm? Or does the arm relax when removing the locking hose? Clearly I don't quite get it yet. BTW, I've spent hours looking in the archives both here and 'the other place' (;)) and found all of the prior discussions very helpful in explaining more than I wanted to know...I especially enjoyed the religious wars between sides defending dd3s and those promoting springs. ;) (Message edited by chucks on November 07, 2007) | ||
| Buswarrior (Buswarrior)
Registered Member Username: Buswarrior Post Number: 1108 Registered: 12-2000 Posted From: 76.66.19.38 Rating: N/A |
Sorry C'9, my fault. Back off the slack adjuster, and the clevis pin will be easily removed, as you have taken the mechanical squeeze off it. The locking rollers are held in the unlocked position (go for a drive) by air pressure, and in the locked position (parked) by a spring. Doesn't matter for chamber removal. happy coaching! buswarrior (Message edited by buswarrior on November 07, 2007) | ||
| ChuckMC9 (Chucks)
Registered Member Username: Chucks Post Number: 1155 Registered: 10-2003 Posted From: 70.3.47.103 Rating: N/A |
Got it. I didn't know the slack adjuster had the ability to move so much to allow everything to get loose when in the applied position. I guess though, that would be the case when one would have brakes that are barely working... Duh! Mah brakes have always been just fine...except for that pesky 10lbs per second the left chamber recently started losing! LOL | ||
| marvin pack (Gomer)
Registered Member Username: Gomer Post Number: 118 Registered: 3-2007 Posted From: 76.4.149.200 Rating: N/A |
chuck why don't you just get new pancakes or diaphrams as some northerners call them LOL and just replace them? when you take them off clean them up and replace both in the chamber and that will save you a lot of money. I bought and replaced mine around 150.00 MCI-8 and I did what was detailed previously. call Luke he has them in stock | ||
| Chuck Lott (Chuckmc8)
Registered Member Username: Chuckmc8 Post Number: 233 Registered: 5-2004 Posted From: 72.152.136.143 Rating: N/A |
Chuck, Mohawk (800-323-7652)has the diaphrams lowest price(and free shipping) Here's the part #'s (4C-5-20 is $63.05) and the other (4C-5-21 is $16.78) You need one each for each DD3. Before you loosen the bands to disassemble the DD3s, be sure to put alignments marks on each piece so that your hoses will line up when you put the can back together (BTDT) HTH | ||
| ChuckMC9 (Chucks)
Registered Member Username: Chucks Post Number: 1156 Registered: 10-2003 Posted From: 70.3.47.103 Rating: N/A |
Thanks Marvin and Chuck. I did consider that, but judging the condition and reading a lot about the other internals that should be looked at and perhaps replaced I figured that that would be a bit much for me right now. For example, the rubber boot over the shaft is competely disentegrated. I'm not challenged by the complexity - I've replaced electronics with hundreds of components and six hours of heads-down concentration time, but I just don't have the comfort level to do this with the actuators. I know enough to know that I don't know enough! From the external condition of the canisters and the lack of attention to the surrounding areas it wouldn't surprise me if they were originals with not much or no attention in their lives. Some of the archives that I spent hours studying strongly encouraged to replace the whole things if there's any doubt. And lastly, I found a helluva deal on remans. I'll post the details assuming all works out. I do appreciate the suggestions though. And upcoming in this project is a complete go-thru of all the components in the entire system and dogonne it, I just ain't got time to become an expert on everything! | ||
| David (Davidinwilmnc)
Registered Member Username: Davidinwilmnc Post Number: 200 Registered: 7-2005 Posted From: 152.20.216.103 Rating: N/A |
On a related note... here's a nice description of DD3 brakes with diagrams. I know this is 'routine' info. for many, and I know the basics of how the DD3's work, but this explained things a bit better than other descriptions I've seen. www.bendixvrc.com/itemDisplay.asp?documentID=2393 | ||
| ChuckMC9 (Chucks)
Registered Member Username: Chucks Post Number: 1157 Registered: 10-2003 Posted From: 68.240.225.30 Rating: N/A |
You're right, David - that was the doc, which combined with da book, was the basis of my elementary steps for removal. That doc has just the right amount of detail for a fundamental overview. | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 288 Registered: 8-2006 Posted From: 207.231.75.253 Rating: N/A |
Chuck, Don't want to beat this to death, but I know it would be much easier to pull the pin with no stress on it, than to back off the slack adjuster with force applied. I have no clue to exactly how the air system would behave when the tanks were drained, specifically whether the emergency application presure would back thru the inversion valve and out the tank drain, or whether the inversion valve would prevent it? So, it seems to me to be a whole lot easier to air up, release the brakes and pull the pin, then bleed the tanks. I have no idea how easily the slack adjuster will turn under load. FWIW, George | ||
| ChuckMC9 (Chucks)
Registered Member Username: Chucks Post Number: 1158 Registered: 10-2003 Posted From: 68.240.225.30 Rating: N/A |
Well I'll tell ya...NOT AT ALL!! I just came in for lunch after climbing out from the coach five minutes ago... and that guy ain't gonna turn at all. I came to exactly the same conclusion. Sooo..., some combination of the techniques above will be done. First thing after my PB&J, will be to release the pressure on the arm & pull the pin. Thanks, George! | ||
| Jim Wilke (Jim Bob) (Pd41044039)
Registered Member Username: Pd41044039 Post Number: 210 Registered: 2-2001 Posted From: 69.77.146.206 Rating: N/A |
Chuck, It might be that your slack adjuster is frozen up or broken /jammed internally. I had one on my bus that was so worn that after you would adjust the brakes, it would jump a tooth inside & that wheel would have almost no brakes. Are you pushing down the lock that is a separate ring on newer designs but on old ones the bolt itself pushes in and keeps the adjustment from turning? It is customary to cover the adjusting bolt with chassis grease after adjusting to keep the water out of the mechanism so the thing isn't stuck next time but that can hide the lock. Jim-Bob | ||
| ChuckMC9 (Chucks)
Registered Member Username: Chucks Post Number: 1159 Registered: 10-2003 Posted From: 68.240.225.30 Rating: N/A |
IT'S DONE! YAY! The adjuster is a separate ring, and it was working fine once I cleaned all the crud away what seems like a week ago. (but that was only yesterday! But the arm really needs to be loose to turn it. Worked like a charm once the pressure was off the arm. I'm glad I didn't try to force it. Seriously, I'd be surprised if the slack adjusters have been done in the last decade. And that pesky outer mounting nut? Long story, but I got 'er loose with a bizarre assortment of extensions, bracing boards and cheaters...without pulling the wheels! Now for the right side, I'm pretty sure the wheels will have to come off. There's even less room because of the driveshaft being biased to that side. Thank you so much, everyone. Like I said earlier this is a job that many of you would yawn through but every little successful step leads to a busnut confident in his equipment. And that's a most valuable thing.   | ||
| ChuckMC9 (Chucks)
Registered Member Username: Chucks Post Number: 1163 Registered: 10-2003 Posted From: 68.240.94.14 Rating: N/A |
And the Other Side! DONE! I'll be back on an extension of this subject in the next couple of days regarding the 1" max movement of the arm (requirement?) and some related slack adjustment questions. Fellers, I couldn't have done it without ya. (I am using the patented, copyrighted & trademarked catskinner adjustment methodology ) | ||
| marvin pack (Gomer)
Registered Member Username: Gomer Post Number: 120 Registered: 3-2007 Posted From: 76.4.149.200 Rating: N/A |
chuck that is so pretty ??? See it ain't so bad after all LOL The most fun is getting in and out gomer | ||
| marvin pack (Gomer)
Registered Member Username: Gomer Post Number: 121 Registered: 3-2007 Posted From: 76.4.149.200 Rating: N/A |
OH! guys, I have always adjusted my brakes this way.. Tighten the slack adjuster up, airup the bus of course, apply brakes to seat the new setting of the shoes and back er off I/4turn and hit the road jack!!! I find that is the easiest and most acceptable at most garages also |