Humming noise near front axle

Jim Blackwood · September 11, 2020, 08:47:20 AM

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

Van · September 11, 2020, 09:30:30 AM

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

chessie4905 · September 11, 2020, 11:55:50 AM

Mine buzzes in quiet shop with airline attached to pressure up.

dtcerrato · September 11, 2020, 02:38:10 PM

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.

Jim Blackwood · September 12, 2020, 08:43:15 AM

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

richard5933 · September 12, 2020, 08:53:03 AM

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.

Jim Blackwood · September 12, 2020, 10:31:20 AM

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?

Jim

richard5933 · September 12, 2020, 11:48:50 AM

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.

DoubleEagle · September 12, 2020, 03:42:55 PM

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.

chessie4905 · September 12, 2020, 05:16:20 PM

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.

Jim Blackwood · September 12, 2020, 05:32:07 PM

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

DoubleEagle · September 12, 2020, 07:44:12 PM

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.

Jim Blackwood · September 13, 2020, 09:34:02 AM

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