| Author | Message | ||
| Jim Rink (Fakeguy)
Registered Member Username: Fakeguy Post Number: 68 Registered: 1-2005 Posted From: 24.33.84.95 Rating: N/A |
I notice that when driving my air pressure continually drops down to about 90, then goes back up to 120 in about a 5 minute interval. This occurs even when driving fairly steady speeds on interstates. I am not aware of any air leaks that would cause this process to occur. I do have an air accelerator and not sure if this is just a result of accelerator use. All input appreciated. Thank you to all | ||
| Dan West (Utahclaimjumper)
Registered Member Username: Utahclaimjumper Post Number: 68 Registered: 1-2005 Posted From: 208.66.38.60 Rating: N/A |
I found that also happening and realized I hadent "blown" my tanks in a long while, after draininf all tanks I had much less swing in pressures and better brakes.>>>Dan | ||
| Dan West (Utahclaimjumper)
Registered Member Username: Utahclaimjumper Post Number: 69 Registered: 1-2005 Posted From: 208.66.38.60 Rating: N/A |
Jim, whats your serial number?? 62 4106-1261.>>>Dan | ||
| James Stacy (Jimstacy)
Registered Member Username: Jimstacy Post Number: 112 Registered: 1-2001 Posted From: 75.63.12.114 Rating: N/A |
You obviously have an air leak. A good air throttle would not cause that much air loss. Time to get the coach up on good ramps or blocks and hook up the external air supply, shut down the engine and LISTEN. Don't forget to follow the pretrip inspection procedure before turning on the external air supply. When my compressor was cycling like that, the check valve from the dryer was stuck open. Time to learn how your air system works. Jim Stacy | ||
| Jim Rink (Fakeguy)
Registered Member Username: Fakeguy Post Number: 69 Registered: 1-2005 Posted From: 192.88.212.34 Rating: N/A |
Jim...thanks for the info...not sure, however, what the pretrip inspection procedure is or how to find out about it Dan 4106-736 | ||
| James Stacy (Jimstacy)
Registered Member Username: Jimstacy Post Number: 114 Registered: 1-2001 Posted From: 76.211.212.84 Rating: N/A |
Jim Go to "Articles of Interest" on this board. R. J. Long has posted a very thorough pre trip check list. Follow it carefully. If you have not found the problem,then get the coach up on some very sturdy ramps or blocks, turn off engine, supply with external air supply and get out the spray bottle filled with kids bubble soap. Remember, you are under a 25,000 pound vehicle, held up only by air suspension! A mistake here could well be the last one you will make! Be certain the blocks or ramps are VERY strong, sturdy solid wood, preferably oak. Block wheels. If you jack the vehicle up be SURE you understand where the proper jack points are and use sturdy equipment. It seems several times a year we lose a bus nut to careless jacking or blocking. It takes a long time to train someone to the point where they understand how great buses are. We don't want to lose any. Be careful. Jim Stacy | ||
| Don Evans (Doninwa)
Registered Member Username: Doninwa Post Number: 88 Registered: 1-2007 Posted From: 66.45.165.58 Rating: N/A |
Jim, Check what happens when you have the parking brakes released too. It may only leak then if you have a bad diaphragm. Of course you need to block the wheels or leave it in gear if it is a standard tranny. Don 4107 | ||
| Jim Rink (Fakeguy)
Registered Member Username: Fakeguy Post Number: 70 Registered: 1-2005 Posted From: 24.33.84.95 Rating: N/A |
Hey Nuts...thanks again for all the good input. I am a scaredy cat anyhow when it comes to jacks in general..will be very careful when blocking and ramping bus. | ||
| RJ Long (Rjlong)
Registered Member Username: Rjlong Post Number: 1313 Registered: 12-2000 Posted From: 67.181.166.160 Rating: N/A |
Jim - If you have any questions about the pre-trip I wrote, PM me and we'll discuss it. Simply click on my name for the email link. FYI, PD4106-736 was delivered new as fleet number 6202 in February of 1962 to Sedalia-Marshall-Boonville Stage Lines, based in Des Moines, IA. Before going thru all the gymnastic repair suggestions, go thru the pre-trip first. If your air system meets the specs outlined in the pre-trip, then it's time to take another freeway ride - with a passenger along for observation - as a diagnostic adventure. If it fails the pre-trip, time to get out the soap bottle! Clue your observer in to what you want him/her to watch and time, preferably with a stop watch. Have a notebook to record findings. Observe the following, at a minimum (again, these should be at freeway speeds, 55-65 mph): 1. At what psi does the compressor cut-in when running on the freeway? (Cut-in = compressor starts rebuilding psi.) 2. At what psi does the compressor cut-out while moving? (Cut-out = compressor stops building psi.) 3. From 120 psi, how long (time) does it actually take before the compressor cuts back in to rebuild back to 120? Observe this several times to obtain an average. 4. When the compressor kicks in, how long does it actually take (time) to build from cut-in psi back to cut-out psi? Again, observe several times to obtain an average. After obtaining 5-6 each of #'s 3 & 4, now get off the freeway and head for some rural secondary roads to repeat the process. If the secondary roads are rougher and more undulating than the freeway, all the better. Report back here with your findings before digging in to repair stuff. FWIW & HTH. . .  | ||
| Jim Rink (Fakeguy)
Registered Member Username: Fakeguy Post Number: 71 Registered: 1-2005 Posted From: 24.33.84.95 Rating: N/A |
RJ...Thank you for the check out procedure. May be a couple of weeks before I get to it, but will and report findings here so others may learn. Regarding the FYI..thanks for the research. I was fortunate to get an actual schedule for her for September 1962, 3 months after delivery, off EBAY . The vents on one of the drivers side bay door still faintly displays the name of the line..most is blocked by the vents cut in for one of the below deck air units and one of the onan 65kw NH GENSETS. She is a fine coach. Thanks again for all your help...will advise | ||
| Jim Rink (Fakeguy)
Registered Member Username: Fakeguy Post Number: 75 Registered: 1-2005 Posted From: 24.33.84.95 Rating: N/A |
RJ. Gathered the data today on run with a buddy. About 30 miles back road and 50 miles interstate. Results were about same for all conditions Pressure builds TO 115 PSI, and then over perioid of about 5 mins average, slowly drops to 95 PSI, At 95 psi, builds back to 115 psi in about 50 seconds This process continues over and over consistenly except for braking. Pressure holds where it was in process after braking and continues in whatever direction it was going before braking. I checked at fast idle also, and results about the same I appreciate your help on this and looking forward to some clues. Thanks again. | ||
| george bruton (Tazman632000)
Registered Member Username: Tazman632000 Post Number: 40 Registered: 2-2007 Posted From: 65.184.69.36 Rating: N/A |
mine does the same thing | ||
| Jim Rink (Fakeguy)
Registered Member Username: Fakeguy Post Number: 78 Registered: 1-2005 Posted From: 24.33.84.95 Rating: N/A |
George...have you done any checks or have any clues?? | ||
| RJ Long (Rjlong)
Registered Member Username: Rjlong Post Number: 1323 Registered: 12-2000 Posted From: 67.181.166.160 Rating: N/A |
Jim & George - Both coaches appear to be operating normally. Remember, as you're going down the road, the suspension is working. As it does, the leveling valves are constantly adding/subtracting air to the bellows to maintain the correct ride height. Both coaches probably have the smaller TU500 air compressors, rather than the larger TU700s found on later model buses. The larger 700s build the air pressure up faster, but yours is still functional, so don't "fix" it. Max psi is a little low, it would be easier to replace the governor on the compressor than to try and adjust the one you've currently got. 120 - 125 is normal, 115 is a little low. Replacement governors are available at any HD truck supply house. Have you done a full pre-trip inspection, including the air brake check? What are your results? Do your coaches pass? If so, great. If not, it's time to get out the spray bottle with soapy water in it. FWIW & HTH. . . | ||
| george bruton (Tazman632000)
Registered Member Username: Tazman632000 Post Number: 42 Registered: 2-2007 Posted From: 65.184.69.36 Rating: N/A |
mine has the manual leveling system ive got a leak in the rear brakes but its only when the treadle is depressed. im thinking maybe something to do with the governer on the compressor, is there a check valve somewhere on the compressor or governer. i check the service manual for clues | ||
| Jim Rink (Fakeguy)
Registered Member Username: Fakeguy Post Number: 79 Registered: 1-2005 Posted From: 24.33.84.95 Rating: N/A |
RJ Thank you for your time and interest in our problems. It is good to know that coach is operating properly and will continue with inspections and checks that you have outlined. Thanks again to you and all that participated in the discussion. I will post any further info I run accross on this matter. | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 299 Registered: 8-2006 Posted From: 76.168.69.233 Rating: N/A |
A little food for respectful thought? Jim did say that the same thing occurred in fast idle, which would take the air use of the air suspension out of the equation. Also, 115 to 95 in 5 min, IS a 4 pound per minute leak, which is too much. Time for soapy water. Another thought would be to hold the foot pedal applied for a couple of minutes while watching the gauge. If pressure stops falling, look at your treadle valve, and or a rear relay valve. PROPER BLOCKING has already been discussed, and we MEAN it! HTH, George (Message edited by George Mc6 on November 18, 2007) |