| Author | Message | ||
| Austin Scott Davis (Zimtok)
Registered Member Username: Zimtok Post Number: 347 Registered: 9-2006 Posted From: 216.37.73.226  Rating: N/A |
My 4104 is not airing up evenly, and as the air drops it settles down unevenly. The passenger side will come up first and then the drivers side will catch up, well almost catch up. I think it is still leaning to the drivers side a little. Is this JUST the leveling valves? And how do you adjust them? . | ||
| FloridaCliff (Floridacracker)
Registered Member Username: Floridacracker Post Number: 413 Registered: 7-2004 Posted From: 67.8.98.138 Rating: N/A |
Zim, Sounds to me as if you have a leak. You should have one leveling valve that supplies both front air bags. The passenger side from the check valve forward doesn't appear to have any leaks and fills right up and holds. The drivers side probably has a leak somewhere and thats the reason it doesn't fill as fast, but will catch up once it is getting all the air from the front tank. Time for a little soapy water in a spray bottle. Be safe. Cliff | ||
| Jack Conrad (Jackconrad)
Registered Member Username: Jackconrad Post Number: 1136 Registered: 12-2000 Posted From: 174.144.153.246  Rating: N/A |
If it is the same configuration as our MC-8, the one front leveling valve controls the height of the front of the bus. The two rear leveling valves control the side to side leveling of the bus. If it is leaning, the problem is in a rear leveling valve (leaking, mis-adjustment, failing). Jack | ||
| FloridaCliff (Floridacracker)
Registered Member Username: Floridacracker Post Number: 415 Registered: 7-2004 Posted From: 67.8.98.138 Rating: N/A |
Zim, For some reason when I read your post I "thought" you said only the front. Jack is 100% correct if you are referring to the entire coach. I stand corrected. Cliff | ||
| Austin Scott Davis (Zimtok)
Registered Member Username: Zimtok Post Number: 348 Registered: 9-2006 Posted From: 216.37.73.226 Rating: N/A |
Yes the whole bus is leaning. My manual shows an adjustable link but the link on the bus is not adjustable. So I think the arm is adjustable. See this photo of the leveling valve. http://i411.photobucket.com/albums/pp194/Zimtok/Buses%20Cars%20and%20Bikes/Valve-000.jpg It looks like the one bolt back by the pivot point is hiding a slotted hole. I'll have to get back under the bus to confirm this. . | ||
| FloridaCliff (Floridacracker)
Registered Member Username: Floridacracker Post Number: 416 Registered: 7-2004 Posted From: 67.8.98.138 Rating: N/A |
Zim, Thats the one. I doubt its an adjustment, probably stuck or gummed up internally. I would remove it and clean it up. I had one that worked after a cleanup and one I replaced. Theres not much too it. I did order the replacement, Of course now it will never break..... You may be able to get a replacement at your local NAPA or truck parts house. Just be safe and get it blocked as it may unstick at the most inconvienient moment. Let us know how you make out. Cliff | ||
| john w. roan (Chessie4905)
Registered Member Username: Chessie4905 Post Number: 1549 Registered: 10-2003 Posted From: 71.58.110.9  Rating: N/A |
You need to do some serious cleaning of those valves; to adjust, you loosen that hex nut beside what looks like a large nail head. The arm is slotted behind the nut. You just move the part behind the arm, according to the direction that is needed. That said, I also don't think that is your problem yet. Could be dirt in the check valve at the leveling valve or leaking air bags- likely. If you want to get serious about fixing this, get a schrader valve like a tire stem. make an adapter so you can bypass your leveling valve/s so the air can go directly to the individual air bags. Inflate each bag at a time. If those bags have cracks in them, go easy on the air pressure!Fill it and see if it holds overnight, at least. Now you have eliminated the bags from your problem or not. Cheap to make up this item and can save a lot of time. Deflate air bag before attaching fitting to copper tube going to bag unit. Make sure to use some soap on the fittings and end of schrader valve to make sure everything is air tight. Da book gives dimensions from stop bumpers for proper suspension height. Some set it a little higher to gain some ground clearance and lessen side to side swaying, although at a slightly harsher ride. If any of those bags are in less than perfect condition with small or large cracks, replace them now. It sucks to try to replace them on the road.Do you have the block off plates on yours? | ||
| Gus Causbie (Gusc)
Registered Member Username: Gusc Post Number: 953 Registered: 11-2005 Posted From: 206.40.238.143  Rating: N/A |
Austin, If you are airing it up for the first time in a long while this sounds about normal for a 4104. Mine does the same thing and if it is the least bit off level it will tilt to one side. It also takes a long time to fully air up after sitting a long time so it appears by the air gage that it is fully aired up before the air bags are fully inflated. After it has been used a while or there is not too much time between airing up it will be ok. What I am saying is to observe a while before making any adjustments right now if it was ok when you used it last. This was GMs first bus air suspension and it has its quirks. Mine often does some strange things and is very slow to air up but with a bit of patience it works just fine. | ||
| john w. roan (Chessie4905)
Registered Member Username: Chessie4905 Post Number: 1551 Registered: 10-2003 Posted From: 71.58.110.9 Rating: N/A |
couple things; of course, it won't start to fill the bags till the air pressure gets to say 80psi and the pressure protection valve opens to admit air to the accessory and suspension system. An air bag that is empty will fill slower than one that is still half full. If only one side in front or rear has been plated, the side still using the beam as air reservoir, will raise slower and drop slower. Also, a restriction, malfunction or dirt in one of the leveling valves can cause problems. | ||
| Buswarrior (Buswarrior)
Registered Member Username: Buswarrior Post Number: 1644 Registered: 12-2000 Posted From: 76.71.101.140  Rating: N/A |
Also consider that the side with the least resistance to motion will move first. And the side that has less restriction in the air line will fill faster. Our old coaches do not move smoothly in the joints after sitting any more than we do! Not a bad time to think about inspecting all the radius rods, if you haven't in a while? happy coaching! buswarrior | ||
| Gus Causbie (Gusc)
Registered Member Username: Gusc Post Number: 954 Registered: 11-2005 Posted From: 206.40.238.21 Rating: N/A |
Austin, The air bags will air up very slowly and usually unevenly and only after the pressure reaches 65psi, only then does the air go to the aux tank. Once the aux tank is pressured up then the air bags begin to fill, they are the very last thing. As I said, the 4104 air bag system requires a lot of patience if it hasn't been used for a while. However, once up and on fairly level ground it will stay up quite a while. I have numerous small leaks but the bags stay up for 3-5 days pretty well since the leveling valve check valve keeps it from bleeding out on level ground. | ||
| Austin Scott Davis (Zimtok)
Registered Member Username: Zimtok Post Number: 349 Registered: 9-2006 Posted From: 216.37.73.226 Rating: N/A |
Well.... The leveling valve is adjustable as mentioned above by John. the bus now sets level once it has aired up completely. It still is leaning as it is airing up. I have one radius rod bushing that is looking a bit out of shape on the side that comes up last. I still haven't had time to do a leak test, so that is next. (I know the brake system leaks when the brakes are applied) My bus will settle down to 30-40 psi overnight (8hrs) and be completely flat (0 psi) in 3 days. . . | ||
| Gus Causbie (Gusc)
Registered Member Username: Gusc Post Number: 955 Registered: 11-2005 Posted From: 12.189.32.54 Rating: N/A |
Austin, 0 psi on the gage doesn't necessarily mean that air bag air is lost, that gage is only for the brake system if it is stilll hooked up as original. There is actually no way to know the air bag pressure, you can only tell by the bus height. Leaning while airing up is normal for my 4104. I don't think the radius rods affect that but they may. If you go under the bus or remove any wheels be sure to check for loose or missing nuts/bolts on the radius rod end plates and brackets. This seems to be a common GMC problem. I've found about five missing so far! Now I'm adding lock washers and/or locktite to them. I assume you know that air is lost every time the brakes are used. You don't say if the system leaks when you apply brakes or when you release them, air is supposed to be released when tbe brakes are released? Your system sounds good to me. My system won't hold 30 - 40 psi more than a few hours, it sure won't do it overnight! Do you mean the bags are flat in 3 days or just that the gage says 0? If the gage is 0 but the bags are still up after three days you have a pretty good system. | ||
| john w. roan (Chessie4905)
Registered Member Username: Chessie4905 Post Number: 1559 Registered: 10-2003 Posted From: 71.58.110.9 Rating: N/A |
The original radius rod bolts had lock wire connecting to them to prevent loosening. Somebody didn't replace it. Now, they mostly use Loctite for this job. Those radius rods aren't going to cause your problems. | ||
| Austin Scott Davis (Zimtok)
Registered Member Username: Zimtok Post Number: 350 Registered: 9-2006 Posted From: 166.137.4.150 Rating: N/A |
As I apply the brake and as I hold it steady I can see the gage drop. The bus air bags loose air so that the bus settles within a day. It is better since I adjusted the leveling valve. . | ||
| RJ Long (Rjlong)
Registered Member Username: Rjlong Post Number: 1580 Registered: 12-2000 Posted From: 98.192.173.82  Rating: N/A |
Austin - Whoa, let's back up a little. You said that when you apply the brake and hold it steady you can see the gauge drop? How much? DOT regs say no more that 3 psi/minute after initial application. If you're losing air pressure faster than that - PARK THE COACH until you find out where in the brake system your leak is. The heck with the air bags right now - you need to find out what's going on with the biggest piece of SAFETY equipment on your bus - the brakes! Actually, before you do anything else, do a complete DOT air brake check as outlined here: http://www.busnut.com/bbs/messages/12262/16203.html?1167072614 (Unless your coach has had spring or DD3 brakes added to the system, ignore the section on emergency brake check.) Once you've mastered and done the DOT brake check, report back your findings. In the meantime, DON'T drive the coach. Period. FWIW & HTH. . .  | ||
| Austin Scott Davis (Zimtok)
Registered Member Username: Zimtok Post Number: 351 Registered: 9-2006 Posted From: 216.37.73.226 Rating: N/A |
RJ, I do not have a 3psi per minute drop. I have to hold the brake for a couple minutes to see the gage drop. The reason I noticed this is because I used a broomstick to hold the brakes on while I checked the slack adjuster movement. (bus aired up with home air compressor to 100-110psi) I still want to track down the leak and also inspect the components even if it falls within the DOT requirements. . | ||
| Gus Causbie (Gusc)
Registered Member Username: Gusc Post Number: 956 Registered: 11-2005 Posted From: 208.54.200.13 Rating: N/A |
John, I know about the safety wire but most drilled head bolts were long ago replaced/lost. I found a couple but none were paired with another? Have you tried to drill a Grade 8 bolt head lately? | ||
| john w. roan (Chessie4905)
Registered Member Username: Chessie4905 Post Number: 1607 Registered: 10-2003 Posted From: 71.58.110.9 Rating: N/A |
Gus, you just need a grade 9 drill bit. | ||
| R.C.Bishop (Chuckllb)
Registered Member Username: Chuckllb Post Number: 898 Registered: 7-2006 Posted From: 75.211.83.214 Rating: N/A |
Huh?...sure, Jonn... Higher the grade, better the pay, right? RCB | ||
| Gus Causbie (Gusc)
Registered Member Username: Gusc Post Number: 995 Registered: 11-2005 Posted From: 71.112.161.107 Rating: N/A |
Austin, I'm on a 3,000 mi trip and had an interesting experience with a leveling valve. I developed a severe port list in WY and, to make a long story short, a rear valve link had come loose on one end. This link originally had a rubber end with a bolt or stud holding it to the valve arm. When the rubber fell out and the link came loose it left a hole about 1" in diameter. This hole is large enough so that if the rubber wears out of both link ends it can cause at least 1.5" of slack in the valve movement and cause slow or uneven airing up!! Sound familiar?? I had noticed for quite some time that this side was slower to air up than the other side but it eventually would even out. This had been going on for at least five months and should have been enough of a clue to make me check the valves and links. Now I know and will closely check all the others when I get home. I also bought a spare leveling valve to carry with me just in case. |