| Author | Message | ||
| Tom Phillips (Fortyniner)
Registered Member Username: Fortyniner Post Number: 1 Registered: 2-2010 Posted From: 66.93.216.253 Rating: N/A |
I was checking the rear brake stroke on my 4905 and noted when the brake pedal is pressed and held there is continuous air hissing from somewhere. The more brake applied the more air escapes. Is this normal? 49er | ||
| John & Barb Tesser (Bigrigger)
Registered Member Username: Bigrigger Post Number: 384 Registered: 9-2007 Posted From: 96.42.5.35  Rating: N/A |
Not to my knowledge. Once the brake is applied and the chamber is full, it should hold it's air. John | ||
| marvin pack (Gomer)
Registered Member Username: Gomer Post Number: 858 Registered: 3-2007 Posted From: 71.53.153.91  Rating: N/A |
Tom, You have a bad diaphram on the chamber. It is a DD3 and while you are replacing one,replace both diaphrams in each chamber. Just posted IBP parts in Apopka FL, Steve Kolb at 1-800468-5287. Gomer | ||
| Ralph Peters (Ralph7)
Registered Member Username: Ralph7 Post Number: 108 Registered: 3-2004 Posted From: 75.244.25.188 Rating: N/A |
You have a problem! You need to find the hiss. Use shop air to air up the bus if possible. BLOCK it! Release the Emg. drake, Have someone apply the brakes, listen at each wheel, you may have a blown diaphram or hose. | ||
| Tom Phillips (Fortyniner)
Registered Member Username: Fortyniner Post Number: 2 Registered: 2-2010 Posted From: 66.93.216.253 Rating: N/A |
I have blocked it and released the e-brake and have shop air connected. The green needle is the one which drops. Yellow one holds. Which chambers are on the green gage circuit? | ||
| John & Barb Tesser (Bigrigger)
Registered Member Username: Bigrigger Post Number: 385 Registered: 9-2007 Posted From: 96.42.5.35 Rating: N/A |
My DD3 leak on my MC5C was not the diaphram (even though I bought some $$$$) It was the O ring seal on the actuator arm. Did just what yours is doing, but like Ralph says find out which chamber and take it apart Before you order new diaphrams. John | ||
| Debbie and Joe Cannarozzi (Joe_camper)
Registered Member Username: Joe_camper Post Number: 251 Registered: 10-2006 Posted From: 99.23.128.160  Rating: N/A |
Could be something as simple as a brake hose. It is service air leaking not emergency air. | ||
| Laryn Christley (Barn_owl)
Registered Member Username: Barn_owl Post Number: 652 Registered: 10-2006 Posted From: 71.254.35.22  Rating: N/A |
I don't know much about DD3s, but I had a air leak at my can. I was about to swap them when a mechanic asked if I had tightened the band around the can. That was all it took, no more leak. | ||
| Buswarrior (Buswarrior)
Registered Member Username: Buswarrior Post Number: 1839 Registered: 12-2000 Posted From: 76.71.102.68  Rating: N/A |
If the gauge has been faithfully connected, the green needle is typically the rear axle. But I wouldn't assume anything with an old coach. There is no need for theory at this point, just listen for where the leak is, use a bottle of soapy water, put your hand up there to feel, get someone with better hearing to source it, whatever. By blocking the coach, what do you mean? Where did you put them? We can't help you fix an air leak via the internet without more information. happy coaching! buswarrior | ||
| Tom Phillips (Fortyniner)
Registered Member Username: Fortyniner Post Number: 3 Registered: 2-2010 Posted From: 66.93.216.253 Rating: N/A |
Ok, the leak is coming from around the lock port on the left chamber. From the manual it looks like there is a check valve in that area. I also noted these chambers have grease fittings which dont seem to ever been lubed. | ||
| Buswarrior (Buswarrior)
Registered Member Username: Buswarrior Post Number: 1840 Registered: 12-2000 Posted From: 76.69.140.246 Rating: N/A |
ok, so is the fitting loose? the airline connection leaking? casing cracked? Go easy on the lube, when they are in good shape, just a couple of squeezes every second blue moon. You may want to do a tear down and clean up of those chambers so you can be confident of their condition. That, and fresh airlines, a new inversion valve and a new relay valve, and there's nothing, air wise, left to think about for years to come back there. If you are doing it a piece at a time, use your favorite anti-seize on all the mating surfaces of the metal bits of the new air fittings, or you get to buy new hoses again next time. Paying a little extra for full fittings at each end of the hoses helps down the road, that way you get two chances to find a fitting that will rotate in relation to the hose, and no winding the whole hose in or out at one end. You'll probably be cutting the hoses to wind the solid rusted mess out of each end. happy coaching! buswarrior | ||
| Tom Phillips (Fortyniner)
Registered Member Username: Fortyniner Post Number: 4 Registered: 2-2010 Posted From: 66.93.216.253 Rating: N/A |
Its not the hose so Ill be pulling it out to fix it. Seems to be coming from what I think is the check valve area but I cant see for sure until its out. | ||
| Buswarrior (Buswarrior)
Registered Member Username: Buswarrior Post Number: 1841 Registered: 12-2000 Posted From: 76.69.142.47 Rating: N/A |
What is this check valve that you speak of? Air to a brake chamber has to be able to go back up the hose it came down... happy coaching! buswarrior | ||
| marvin pack (Gomer)
Registered Member Username: Gomer Post Number: 862 Registered: 3-2007 Posted From: 71.53.153.91 Rating: N/A |
Oh TOM!! Least we forget, WELCOME TO THE WONDERFUL WORLD OF BUS NUTS We hope that your stay is good and you have info you will share with is so we will get smarter LOL Some of us need more, believe me on that. Gomer | ||
| Tom Phillips (Fortyniner)
Registered Member Username: Fortyniner Post Number: 5 Registered: 2-2010 Posted From: 66.93.216.253 Rating: N/A |
Hi, work interfering with life again. bad habit. My DD3 diagram shows a check valve in the service chamber. Since Im a NBN (New Bus Nut) I have to build two ramps and get a monster impact wrench to safely get to the brake chamber. Hopefully by this weekend. Once I have it on the bench Ill verify it has a check valve and post a little photo. -Tom P. | ||
| Tom Phillips (Fortyniner)
Registered Member Username: Fortyniner Post Number: 6 Registered: 2-2010 Posted From: 66.93.216.253 Rating: N/A |
Heres a shot of the chamber with the "check valve". Air applied to service port leaks around right side of image. Also, clamp bolts are frozen solid. Are those available separately?  | ||
| Tom Phillips (Fortyniner)
Registered Member Username: Fortyniner Post Number: 7 Registered: 2-2010 Posted From: 66.93.216.253 Rating: N/A |
Here is the leak. Also note the broken spring.   | ||
| L James Jones Jr (Jamo)
Registered Member Username: Jamo Post Number: 145 Registered: 11-2007 Posted From: 24.59.114.207  Rating: N/A |
What leak? Looks like it's full of air to me... Ha...sorry... |