| Author | Message | ||
| H3-40 (Ace)
Registered Member Username: Ace Post Number: 1382 Registered: 10-2004 Posted From: 174.252.133.243  Rating: N/A |
Bus airs up fast until it gets to about 75-80 lb then slows way down unless I put it on fast idle and then it goes to about 100-115 very slowly but eventually goes up to about 135 +- Ok once I release the parking brake, the air drops about 25 lb but will eventually go back up very slowly. Now if I have the parking brake off and apply foot pedal about 4-5 , (maybe more) times the air is down to almost where the buzzer comes on, actually it did once! I try not to use the brakes a lot while parking or backing up to a trailer just to save air! Now my question is, after talking to a mechanic today he said he just had a H3-45 Prevost come in with a very similar problem and the guy was pissed because he had just had the air drier replaced and thought they should have checked everything! My mechanic said he drained all the air tanks and recovered about 5 gallon of water! My air drier was replaced about 6-7 years ago and don't know if the tanks were drained then but I know I have never done it and my mechanic knows he's never done it since he's been working on my bus sooooo Is this a possibility that is causing my air to drop suddenly as described? He says if the tanks are full or Partially full of water the reserve air that the brakes actually use is not there so what air IS THERE is used up quickly. I think that's what he said! The brakes work well and don't leak down when sitting at a stop. They only go down if I continuesly use them in succession. | ||
| George M. Todd (George_todd)
Registered Member Username: George_todd Post Number: 1314 Registered: 8-2006 Posted From: 76.94.209.14 Rating: N/A |
Ace, Your mechanic is right about water taking up air space in reservoirs. If that were your only problem however, the bus would air up twice as fast, because there was less storage space. (You can't compress a liquid.) The increase change says you have just developed a leak somewhere in your auxiliary system, and the pressure buildup slows down because the protection valve opens about 75-80psi, and allows air flow to the auxiliaries, and then you are leaking air out a rear air bag, or somewhere else that you don't hear. G | ||
| RJ Long (Rjlong)
Registered Member Username: Rjlong Post Number: 1881 Registered: 12-2000 Posted From: 71.195.175.142  Rating: N/A |
Ace - Gotta agree with George on this - sumpin's leaking downstream of the PPV. It also concerns me about the large psi drop when you release the parking brake. (Remind me - drive axle brakes spring or DD3s on your coach?) Is there any way you can use a shop compressor to air up the coach? That way you don't have to try and hear something over the engine noise. If you can drain the air tanks yourself before starting additional troubleshooting, that would give you an empty system, thus possibly more accurate assessment. IIRC, there are some DOT standards about air system recovery times, might be useful as a guide. Can't recall where I've seen them, tho.  Perhaps you can enlist Bud with his superior hearing ability to assist? Or at least supervise? Good luck, hope you find the problem. FWIW & HTH. . .  | ||
| H3-40 (Ace)
Registered Member Username: Ace Post Number: 1383 Registered: 10-2004 Posted From: 174.252.133.243 Rating: N/A |
Putting it in the shop at 7:30 am to have it looked over. Thanks | ||
| Bill 340 (Bill_340)
Registered Member Username: Bill_340 Post Number: 182 Registered: 7-2006 Posted From: 75.203.72.180  Rating: N/A |
check the govenor on the air compressor, our eagle did that once and that solved the problem, | ||
| Brian Evans (Bevans6)
Registered Member Username: Bevans6 Post Number: 126 Registered: 5-2009 Posted From: 65.92.51.73 Rating: N/A |
Since it was brought up... Compressor recovery test per DOT here in Ontario is: with bus completely aired up, suspension full, etc, engine at 1,000 rpm, fan the brakes down to 80 psi. Compressor kicks in, measure the time it takes to air up from 85 psi to 100 psi. Should be less than two minutes here, may be different in other locations. My bus takes 18 seconds, or thereabouts. Tanks should be drained of water every service day. Part of daily inspection, as is doing the compressor recovery test. I keep a log of every day my bus is driven, and I note the compressor recovery time in the book. I keep fuel usage, start/stop mileage, locations, and note major maintenance. No reason not to do things in a professional manner, makes me feel like a real driver! | ||
| Buswarrior (Buswarrior)
Registered Member Username: Buswarrior Post Number: 2245 Registered: 12-2000 Posted From: 174.89.179.92  Rating: N/A |
In high humidity Florida, you haven't drained the tanks? As the ocean inside your tanks has risen, the looser of the oily gunk that is always in there, floats on top, so when the rising tide reaches the airline fittings, guess what goes down the pipes first? The stiffer and heavier bits accumulate on the bottom, like the tidal mudflats at the sea shore. When the air system is being assembled, along with the rest of the coach, the left over burrs and scrap bits from manufacture have a bad habit of finding their way into all sorts of places. Metal bits stay at the bottom of the tank... Does DOT plastic airline scrap bits sink or float? And then try stuffing all that gunk and potential floating solids through a check valve and all of the other small orifices of all the other valving? This is no pure and virginal surgery environment, and certainly not what gets told in driver training class, cuz the trainer never saw underneath, this is the harsh world baby! Busnuts, drain your tanks regularly for more reasons than you can dream! happy coaching! buswarrior | ||
| Luvrbus (Luvrbus)
Registered Member Username: Luvrbus Post Number: 1369 Registered: 8-2006 Posted From: 184.10.153.249 Rating: N/A |
The unloader valves are probably the culprit Ace if the drier is in good shape,servicing the drier will most likely cure your problem. The H-40 has a complicated air system great system but can be a PITA took me days to find out the front system on the dual air system on a H-40 that the front has priority on that system good luck hope it easy fix for you | ||
| H3-40 (Ace)
Registered Member Username: Ace Post Number: 1384 Registered: 10-2004 Posted From: 174.252.133.243 Rating: N/A |
Just leaving the shop. No water in tanks at all but found a leaking tag axle air bag! Will replace four when we return! | ||
| john w. roan (Chessie4905)
Registered Member Username: Chessie4905 Post Number: 2234 Registered: 10-2003 Posted From: 71.58.71.157  Rating: N/A |
GM recommends to allow tanks to drain overnight if practical to get more oil/gunk to drain out. | ||
| Dave Walker (Chrome_dome)
Registered Member Username: Chrome_dome Post Number: 443 Registered: 3-2010 Posted From: 74.41.14.235  Rating: N/A |
Ace it was the weight of all the new tile at the steps you put in , LOL Dave | ||
| H3-40 (Ace)
Registered Member Username: Ace Post Number: 1385 Registered: 10-2004 Posted From: 166.248.139.129 Rating: N/A |
Ha that's the second time I've heard that but no, they are pretty old! Were playing like carny's and poppin corn at a huge BG event this week and when we get back, I'm going to order four new air bags for the rear. It has six but the two hardest ones were done a year or so ago! Then mIght look at the two front bags but it appears they are in good shape for now anyway! |