I have a leak somewhere on the passenger side air bag system, I have checked the air bags and level valves no leaks found, I did have a leak on the engine shut off valve, replaced it, and it still leaks down, The drivers side will stay aired up for months, the passenger side will go down overnight! any Ideas?? >>>> John.
While I'm not familiar with your particular breed of bus, it's not uncommon. it could be a leak in the air bag seals or bags themselves. If you have air beams, it could be a leak there. It could be the leveling valves leaking out or back through the valve. If you can't find it with soapy water, you could try putting a shutoff valve in the lies temporarily to isolate it. Might have to move the valve a few times to narrow it down. Otherwise, for a leak that slow, it may not be a problem.
Had the same thing on our last bus. Nothing magical about it - just follow every line and spray with soap water looking for the leak. Got to be one somewhere, but they are often difficult to see. Have you tried using a mechanic's stethoscope to listen for the air escaping?
If you're going down overnight the leak should not be totally impossible to find. Mine took about 4-5 days to drop and I ended up taking it to the shop so they could put it in the air and do a more thorough search. Ended up being a leak at a fitting in the copper line. I've got one on our current bus that I'll start looking for once the weather warms a bit more.
Good luck.
I suspected the level valve from the start but I soaped it down and found nothing, unless its bleeding through the valve and back through the compressor? is there any check valves that could fail? I will try listening with a stethoscope when it warms up a little! this cold weather really complicates things!! >>>> John.
Quote from: goutoe on February 12, 2018, 01:15:26 PM
I suspected the level valve from the start but I soaped it down and found nothing, unless its bleeding through the valve and back through the compressor? is there any check valves that could fail? I will try listening with a stethoscope when it warms up a little! this cold weather really complicates things!! >>>> John.
Not sure about the leveling valve on your bus specifically, but in theory that is possible. There is a check valve of sorts inside the leveling valve according to what I've been told. I'm sure that others here have more experience and can address that more fully.
Inside each leveling valve you have a valve. The same kind of valve you have in your bicycle tire.
If you check everyting with soapy water and noting appear.....remoove this valve and clean or replace it. The valve is situated on the entry side of the leveling valve. If this tiny valve is defect,the air from airbags will return to the suspension reservoir.
Thanks guys, I will go back to the leveler valve and start there.>>>> John.
I diagnosed mine a few years ago with an adapter to isolate the air bag before I fooled with leveling valve and lines. I used a Schrader valve to add air to bag with adapter to line going to bag. Pumped it up to about 80 pounds and left it set overnight. I would recommend a longer line to connect to the airbag. You don't want to be close of one decides to blow. It will, at the minimum, ring your bell big time. It was flat next day. Be sure to soap connections to air bag and Schrader valve to avoid a false positive.
Chessie, I may try airing up one bag at a time, I will take your advice and use a long hose lol. I wouldn't want to be close if one blew!!Thanks.>>>> John.
Quote from: goutoe on February 13, 2018, 12:21:39 PM
Chessie, I may try airing up one bag at a time, I will take your advice and use a long hose lol. I wouldn't want to be close if one blew!!Thanks.>>>> John.
Unless your air bags have been plated, you can't easily air them up one at a time. They are in pairs, connected to the air beams. You fill the air beams and both bags inflate.
You sure about this Gumpy? It is an AM General from his info.
Quote from: chessie4905 on February 13, 2018, 04:03:02 PM
You sure about this Gumpy? It is an AM General from his info.
Oh, yeah. Forgot what we were dealing with here. Was thinking it was an MCI. Different thread, I guess.
Well, I retract what I said previously.
You sure about this Gumpy? It is an AM General from his info.
Sorry about that twice, didn't know that was possible.
Can someone help me understand? When the OP says one side can stay aired for months, that confuses me. I have a MCI and as soon as I turn it off, I start to lose air. I think after about 5hrs or so, it's completely down. As soon as I park and shut it off, I have to put blocks under for my leveling. Do other busses stay aired differently?
Maybe his bus stays leveled by air?
My 4905 has held air for almost 6 months.
The air bag system is separated from air brake systems by valves and checkvalves. If the leveling system is tight, the bags will stay inflated, even though the air in rest of systems leaks out. The leveling valves have built in check valves to keep have pressurized. Generally, the front air bags (4) are controlled by one leveling valve. The rear airbags, have two leveling valves, each controls bags (2) per side. So, if you have a leak, it can be: bag/s keaking, leveling valve/s leaking, or lines to have from leveling valves.You can have one more more leaks at the same time. Also on older MIC and GMC's the bags are attached at the top to hollow long rectangular air beams. The idea was that the hollow beams contained additional compressed air volume to provide a compliant ride. However time and corrosion and dust over the years caused leaks in the beams which were very difficult and expensive to repair. Someone devised plates that mounted between top of bag and bottom of beam to deal with this. The air volume is definitely less and makes the ride firmer, so they say. On the older busses, you can't isolate bag from beam as far as which is most likely leaking, so most will replace all 4 bags and install the block off plates at the same time. The coach could oscillate some over bumps if you only did one side (2). You may get lucky and it is just a leaking line, but I doubt it. Like carries all the parts. Btw, the block off plates have gone up in price significantly in past few years. They are anodized aluminum and 1/4 or 5/16 thick.
I do have a hydraulic leveling system that helps keep the weight off of the suspension, but the right side bags go down overnight the left side stays aired up between uses, even if my dash gauges drop to zero, somehow the leveler valves hold the bags full or at least partially full for some time.
Leveling valves have built in valves that won't allow leak back unless lever move (due to suspension change in height) opens to admit or release air. If it opens to admit air and air pressure in supply line is less than pressure in bag, then air will go out of the bag back into air source line till either pressures equalize or bag deflates partially or completely. So either bag of line from leveling valve is leaking or leveling valve is defective.
Yes Geoff, I am also confused;too much to do a reply to him. More info needed.
Sometime,the little valve inside the leveling valve is simply not there. Or at the wrong position. Poeple often remove this tiny valve and simply do not installed back in place. You have to check carefully to see this valve.
The close circuit of air in the rear and front suspension is create with thoses little bycicle tube valve.