So I got my 110v compressor installed, it takes awhile to pump up but switches off at 130 and the automatic drain blew at the exact same time. So that's all good. But while it was pumping up I got some funny noises from up front.
First, at around 80psi there was a fairly loud buzzing noise, which went away when I switched off 28v power. Then at about 120psi there was a humming noise regardless of power and when I touched a stethoscope to the curb side air tank behind the axle it sounded a lot like an electric motor running. Then when the compressor shut down and the drain purged all went quiet. Main power on, main disconnect on, no noise at all that I could hear.
For those of you who have lived with the DL3, does this sound normal? Anyone know what was making the noises?
I'll get a photo of the compressor install and post it.
Jim
Ive heard that sound when pumping up the coach from external shop air. Mine comes from the protection valve under driver in compartment. Goes away once it opens to allow air to air suspension and accessories.
My bus has several 1-way air valves, which hum and buzz and make other noises while the air is flowing through the system (while airing up). Yours probably does too.
A loud buzzing noise that is on with the power is likely a solenoid? I'm not sure what it would be for though. Could also be a low air alarm, but I would guess you know what the low air alarm sounds like on your bus.
Could you be hearing some of the sound of the compressor itself telegraphing though the bus? Especially if you used hard piping to connect?
Otherwise, my bus makes similar noised up front as the engine airs things up. Quite noticeable just before the auxiliary tank opens and just after it opens.
That is normal for the DL the air dryer is in the front by the axle the low air buzzer is in the panel on the drivers side and are adjustable for different sounds when the pressure was built up the buzzer went off is why there was no difference with power off or on
OK thanks. Pretty much normal then I guess. The compressor cycles a lot sooner than will be acceptable for camping so I must have leaks somewhere. Here's a shot of the compressor and one of the bus up on stilts. I'm going to let it sit like that for a day or two before getting underneath. The stands are sitting on 18" diameter 1/4" plate just to spread the load a bit. The rear has two 6x6 blocks up under the frame on each side to lift it up. I used the "rear raise" switch to lift it and then block it. Been sitting like that for a couple weeks now.
Are there some places these are more prone to leaks than others? Right now it takes about 1/2 hr to pump up and probably less than 10 minutes to cycle back on again.
Jim
Where to look?
I started at one end and tried to follow every line I could, even in the tunnel and behind panels if they were removable. Surprising how a 1/4 turn on a fitting can make such a big difference.
Wiper motors and especially control valves (if you have air wipers) are notorious. Air bags, height control valves, etc, etc.
Remember that it's possible for height control valves to leak internally if the check valve is failing - it's difficult to find the leak since it sends the air back to a tank and not externally leaking.
Does your bus have air controls/lock for the door?
HI;
I also have an MCI (7). When using shop air to air up the system, I also hear it "humming".
I just call it '' the bus is singing". Stops after the air bags are up.
:) :)
Anything could be leaking. The previous owners would have fixed the "most common" leaks already, so I think you just have to listen for escaping air, I would expect it to be pretty obvious at that leak rate. From my experience, valves with internal seals are prime suspects, but any tank could have a hole rusted in it, or any line could have a hole poked in it.
General locations to listen:
- Front axle
- Spare tire compartment
- Under the dash
- Rear axle
- Engine compartment
The little compressor take longer to air up the suspension,the engine compressor is at least 12cfm your portable is probably4,5 or 6 cfm
Yeah, maybe even 3. I'd have to look. At least it's made from good old cast iron so it should live awhile.
Messing with the compressor, jack and jack stands has made my back a little sore so I'm going to give it a rest for a day or two, maybe play with a CAD program a little on those tank drawings. It'd be nice if I can give them something better than sketches to work with. I'm thinking 3/8" plastic might be the way to go on those.
So if I'm interpreting the suggestions right, maybe my first move is to go over all the lines and snug them up at the ends while listening and feeling for air. I have this neat gadget that's used to check for water leaks in buried lines... It's kinda like an amplified stethoscope. Maybe it can help. If there's a valve leaking I hope I might be able to hear it with that. The air bags all look to be in pretty good condition. I already gave the tire well a once over. Well, I should know more in a couple days.
Jim
My leaks in my 1981 were:
- rusted through parking brake tank
- inversion valve internal seal
- an air bag
- push/pull valve interval diaphragm
- rear suspension leveling check or relief valves
- wiper controls when the air pressure is around 70-90 psi
They all hissed quite noticeably to someone standing next to the bus, except maybe the push /pull valve. However it was frequently a lengthy search to pinpoint the actual leak.
I did not find any leaks at fittings. But others have.
I would recommend starting by listening for escaping air.
If you become serious about every leak:
Others have talked of soaking all their lines with soapy water. This will help for slow quiet leaks but sounds very tedious.
If you can identify how the subsections connect, you can isolate them with caps and plugs and a pressure gauge and hopefully reduce the amount of lines that need to be checked.
In the self inflicted wound dept...
"Tightening" fittings for no apparent reason is way down my list of remedial actions.
Snap one and you've got unnecessary project distraction.
Go find the noisy ones first, and see where you're at before making work?
Happy coaching!
Buswarrior
I went through the brake system on mine last year. Found several leaks. 3 were lp3's. Two were an incredible bitch to replace. Up behind last step to main floor. No longer accessible from above, had to get to them from below. Another leak was a main inline check valve. Used Harbor freight stethoscope without the amplifier attached along with leak detector liquid that ac supply stores carry. It works better than soapy water. Has glycerin in it, so it stays in place longer. Bendix recommends every air system component to be rebuilt every several thousand miles. When was the last time yours were done or any other coach here? I rebuilt or replaced the majority of mine. The worst was the module at rear axle. Several different components there. Or we can wait till many of the components are finally unobtanium. I ran into this with the inversion valves. The one type is no longer available, even from Luke. I ended up buying a new one and swapped spring and shims from old one. Even so, it took three months to get the new one. They had to make more.
BTW your air bags and such don't start filling until the brake system has about 80-90 psi so that could be why some of the noise starts them as the "accessory" system starts filling.
;D BK ;D
Thanks BK, that probably explains it. I rolled around under the bus the other day and didn't hear any air spewing out, ditto the engine bay and dashboard area. So that got me thinking. My hearing may not be good enough to find the little leaks, and I've ALWAYS had air leaks in everything from tires to shop air so who am I trying to fool thinking I can use the air suspension to level the bus? I'm not the guy who manages a perfectly leak free system. Well I did eventually get the tires on the tractors and such to stop leaking by using Berryman's but that isn't safe to use on air lines I don't imagine.
So I've been looking at electric screw jacks. I figure a 10 or 12 ton unit should do the trick, three of those and I can stop worrying so much about the air. Anyway I'll see how that goes. Bulkier than hydraulics but no leakdown. I'm hoping to find them for around $700/unit but not quite there yet.
Jim
BK is correct. I've had this issue with my Model 15 and the H3, no leaks and always when the acc tank started filling. I always thought it might be caused by a gummy/sticking check valve. Are you getting much moisture from the air drains? Just something else to ponder ;)
Mine buzzes in quiet shop with airline attached to pressure up.
A lot of the buss compressed air OEM check valves with the metal disc spring loaded on a metal seat notoriously buzz with passing air - very normal. The smaller CFM of shop compressors make then buzz even more. Very normal IMHO.
That is what I'm hearing no doubt. The bus sings. That's good, I know it's happy.
Too bad I can't hear the air leaks but I may be able to live with them. It takes about a day for the airbags to leak down. That's too fast to use them for leveling when parked but not too fast when driving or so it would seem.
Jim
If there are no visible signs of leaks from the air bags and ride height valves, there's a chance that the ride height valves are leaking internally. You don't hear the leaks and they don't show bubbles, because the leaking air is just being sent back into the tanks.
When you have things up on blocks next, swap out the ride height valves if you haven't already done that. They're cheap enough and then you will know they are not the problem. Our '74 bus will stay up on its air bags for months (knocking on wood as I type this) so I know that it's possible to remove the leaks in a system if you keep at it.
I pulled a "trollguy" and watched a utube video on repairing level valves so now I'm an expert and know all there is about valves of all types, right? In fact I think probably I know everything about all air systems ever made now since anything that wasn't in that video is just for troglodytes anyway. I probably also now know everything about everything now so I can quit messing about with buses and go solve world hunger, violence, war and politics all in one stroke. Bow down to me, I'm the greatest. I will rule you all with.... I was going to say kindness but that would not be in keeping with my great guide and mentor so Instead I'll say arrogance and cruelty. Yep, that should do it. OK minions, do my bidding.
Now where was I? Oh yeah, important things like air leaks.
I am just flat amazed that anybody can retain air for a month at a time. Richard you are my new hero. (I'm not sure you want to be.) So from that video it appeared that just 4 o-rings are all that's needed to restore the leveler valve. Even I could probably do that, and the bus is up on stands so access isn't a problem. At least I can have a look and see if new valves are a good idea.
I also do have the air controls and latch on the door. But I don't hear any air around it either.
My front level valve sends a signal to the box in the front bay that houses the kneel controls. Not sure how the rear is set up.
OOOps!!! did I accidentally say there might be something I might not know?!! Oh no! Whatever will I do? ;D
Jim
Check the price on the new valves before you spend too much time on them. Depending on which your bus uses, it might not be worth the time. Especially if the valves are looking corroded or worn in any way.
The GM books show in detail how to rebuild the OEM valves on our buses, and I've yet to have anyone tell me it's worth doing. Mine were replaced with a more modern valve shortly after getting the bus.
Yeah - being OCD has it's advantages. When I brought my bus home it would settle on one side in just a couple of days. That was not going to work, since we have no way to level in a campsite and rely on boards under the wheels. Trying to get the bus to stay aired up long enough for a week of camping brought me to the point where I just kept chasing down leaks. Now I'm slowly working my way through the plumbing on the accessory tank so that it stays at pressure for at least a long weekend so I can work the pneumatic step cover.
Most of the initial leaks were a few fittings on the copper lines that had come loose over the years, and I believe a couple in the engine bay. The ride height valves were the last leaks we found since they were leaking internally. If you have the tunnel opened up, you can see how many couplings get used to put a bus together. Just takes one that wasn't fully snugged down to create a problem later on, or one bad repair along the way.
When I park the bus in the fall behind the barn it's up an all corners. When I pull it out in March it's still standing tall.
Quote from: Jim Blackwood on September 11, 2020, 08:47:20 AM
So I've been looking at electric screw jacks. I figure a 10 or 12 ton unit should do the trick, three of those and I can stop worrying so much about the air. Anyway I'll see how that goes. Bulkier than hydraulics but no leakdown. I'm hoping to find them for around $700/unit but not quite there yet.
Jim
I'm not picturing the electric screw jacks, but it sounds like a workable solution. I have toyed with the idea of using trailer landing gear with either a hydraulic or electric motor to drive them. They would have much more capacity than needed for leveling, but would be capable of lifting the bus up for tire changes or servicing. Good ones are pretty expensive, but I happened on a set of four new ones at an auction for one hundred something. Two in the rear and one up front would do it. The hydraulic Big Foot's are slick, but they cost a lot.
Yeah, Irebuilt 2 several years ago. Had to special order the glycerin, of which I still have some somewhere. A royal pita for what new ones cost nowadays. If I have a bag leak, I like to attach an adapter to the air bag inlet line and fill the bag with the Schrader valve attached to the adapter. Check it next day to see if it is still rock hard. Easier to check since I have a pit.
I'll see if I can get some part numbers off one. Generically the cost seems to be around $60 not that it means anything.
I figured some of you guys had given this leveling business some thought. The landing gear idea certainly has some merit. I should probably look into that as well.
Right now the sales manager for the Chinese company I'm in touch with is trying to pull a bait and switch on me but I'll let it run it's course. I suspect landing gear might just be a better choice overall. I'll have to talk to my brother about that. That and a gearmotor could be a good combination. There is a truck dismantler locally so this has possibilities. The height could be an issue but I'm pretty sure it can be cut down if necessary but maybe it wouldn't be. I sort of like the idea anyway.
Jim
From what I have seen of screw jack listings, they have tremendous lifting capacity, but they need lateral guide rails if there are any side way forces. The landing gears are tougher and can be braced if necessary, but they might need more space to mount. There is also the possibility of retaining the hand crank in case of power failure. The ones I have are Jost Magnum A440's, and weight about 80 lbs. a piece, which I think is favorable compared to hydraulic units. They have a travel range of 14 to 19", and have a lift capacity of 62,500 lb. The main problem is finding appropriate locations to mount them in, and getting them at a good price. New, they are $400-$700, each. I like this model because the gearing is all internal instead of a bulky external gearbox on top, but there are many models and brands.
I've started looking. Prices look pretty good even new. Can't imagine why used wouldn't work just as well. So I have a mounting question then. Looks like there might be room between the duals and tag axle IF the tag doesn't hit when it turns. Anyone know off hand how far the tag turns on a DL?
Jim