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Old 10-30-2017, 04:35 PM   #1
Skoolie
 
Join Date: Aug 2017
Location: Phoenix, AZ
Posts: 228
Year: 1997
Coachwork: Blue Bird
Chassis: AARE 3903
Engine: Cummins 8.3L 12v
Rated Cap: 78
Air Leak Front Drivers Side

Just wanted to put this out there in case anyone had seen similar and could help narrow my search. Still very new to my bus ('97 BB AARE, air brakes, seat and door but not springs), so lots of things to get familiar with.

Started the bus up this morning and noticed a hissing sound from the area of the drivers side front tire during my walk around that I didn't remember hearing before. Reaching in over the tire I can feel air blowing, but it almost seems to be coming from up near the body rails under the floor rather than from behind the wheel. I don't see any air lines or components up there, but will have to climb under there tonight and dig around some more.

When I backed out of the driveway to head back to storage, it did seem like I was losing a lot more pressure after/during braking. Just sitting (brakes off) it will build up to 125psi, but after 2-3 applications and holding the brake in I was already down to 100psi. So it certainly seems like a significant leak in the compressed air system. Still have to do some more work to figure out the exact circumstance of the leak, but the air blowing outside is felt continuously. So it may be all the time, but the additional loss from braking is more than the compressor can keep up with. Ended up putting it back in the driveway as seemed like a bad idea to drive. Air blowing still felt / heard after setting the parking brake and turning off.

Thanks for any pointers on things to check, otherwise I'll report back with what I find tonight.

Rob

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Old 10-30-2017, 05:34 PM   #2
Bus Geek
 
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Rated Cap: 72
Take a look in the electrical access panel and see if you can see air lines running in the lower right corner.

If I recall, there are air lines & fittings there on my 2001 AARE. If they were leaking I would expect the air to be coming from above, and a bit forward of, the drivers side steer tire.

Failing there, I would crawl underneath and start following brake and air seat lines.

From what you describe I don't think it would be your brake can.

Hopefully someone more familiar than I am will chime in.....

Good luck.
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Old 10-30-2017, 06:58 PM   #3
Skoolie
 
Join Date: Aug 2017
Location: Phoenix, AZ
Posts: 228
Year: 1997
Coachwork: Blue Bird
Chassis: AARE 3903
Engine: Cummins 8.3L 12v
Rated Cap: 78
Thanks Steve, appreciate the thoughts. I wouldn’t have thought to look in there. That reminds me also that the stop sign is air powered, which is mounted in that vicinity too.

I’ll try to get a picture up of where it feels like it’s blowing from. Should have taken one earlier but was in a rush. As I recall there are a bunch of hollow metal rails running perpendicular to the frame under the floor (what I’m correctly or incorrectly calling body rails) and it almost seemed like air is blowing out of one of those into the wheel well from somewhere further amidship.

Will try to clarify when I get home. Was a hectic morning when plans to move the bus ran aground ;)


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Old 10-30-2017, 09:53 PM   #4
Skoolie
 
Join Date: Aug 2017
Location: Phoenix, AZ
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Year: 1997
Coachwork: Blue Bird
Chassis: AARE 3903
Engine: Cummins 8.3L 12v
Rated Cap: 78
Air Leak Front Drivers Side

Well, I found the source, and my missing air tanks! [emoji6]

I was always surprised that I could only see one through the hatch under the drivers window. The other two are hiding between the frame rails between the spare tire and the fuel tank. There is a component venting air directly toward the drivers front tire on top of the rear most tank.

Where I was feeling air from:


What’s hiding between the frame rails (from spare tire looking toward rear:


The component that’s venting (from the small off center hole, not the larger center hole):


Interestingly it had held 100psi all day, and didn’t start venting until I started up and it was up to maybe 110psi or so. I’m wondering if this is some sort of over pressure valve that’s gone wonky and is venting at too low a pressure? I’m guessing the rear most tank that it’s attached to might be the “wet” tank. Both the mid and front tanks have drain valves at the bottom, this one doesn’t. It also has a serious looking hose coming in the back end of the tank:



Time to go find a parts diagram if I can, to try and sort out what’s what.

Rob


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Old 10-30-2017, 10:36 PM   #5
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Good sleuthing. PNW_Steve is right about air lines in the electrical panel; mine had a pair of valves in there too. They operated the service doors.

Looks like that whatever-it-is has a good coating of fuel/oil and dirt. Wipe it clean and you may find a part number right on it. If you can find a string of digits, perhaps 7 of them, it may well be a Bendix part number you could search for online.

The part will likely have to come out one way or another, so maybe just go ahead and pull it when you're at a point that the bus can just stay parked for several days while you identify it and source a replacement. Or, if you're like me, you might take it apart "for science" to see how it used to work, possibly clean a speck of dust out of it, and find that after re-assembly it works again and replacement isn't necessary..
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Old 10-31-2017, 07:46 AM   #6
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That's a pressure protection valve that feeds all non essential air items(seat,stop sign, horn, etc.) It cuts in at 70 psi and cuts back out at 60.
It's there to protect the braking system air pressure so you can still stop safely if your accessories massively leak.

That looks like a haldex version and not a bendix but either brand should interchange with the other.

Haldex number was always kn31011 I think but verify what you have before purchasing anything.
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Old 10-31-2017, 07:49 AM   #7
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booyah hit the nail on the head.. and those protector valves go bad.. I had one on my red bus that had frozen (due to no air dryer), last year and it started leaking like that..
-Christopher
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Old 10-31-2017, 09:52 AM   #8
Skoolie
 
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Thanks!! That gives me a lot more to work with.

Rob


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Old 10-31-2017, 12:52 PM   #9
Skoolie
 
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Chassis: AARE 3903
Engine: Cummins 8.3L 12v
Rated Cap: 78
It looks like Haldex has discontinued the KN31000 series.

The current replacements seem to be:

90555396 - Open 70psi, Close 65psi (Noted as replacement for KN31011 and KN31000, but without auxiliary ports)
https://www.haldex.com/en/na/valves/...lves/90555396/

90555397 - Open 85psi, Close 80psi
https://www.haldex.com/en/na/valves/...lves/90555397/

90555398 - Open 95psi, Close 90psi
https://www.haldex.com/en/na/valves/...lves/90555398/

These are also available with a one way check valve:
https://www.haldex.com/en/na/valves/...lves/90555409/
https://www.haldex.com/en/na/valves/...lves/90555410/
https://www.haldex.com/en/na/valves/...lves/90555411/

I'm guessing the 90555396 is the one, but I'll try and pull the old one and verify part numbers.

Rob
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Old 11-01-2017, 01:19 PM   #10
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And THAT, ladies and gentlemen, is the difference between skoolies.net and Facebook. I really like you guys and am glad you haven't kicked me out/let me back in 3 times.
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Old 11-03-2017, 03:48 PM   #11
Skoolie
 
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Chassis: AARE 3903
Engine: Cummins 8.3L 12v
Rated Cap: 78
Got a replacement valve from my dealer and started disassembly last night. Probably should have seen it coming, but seems its not nearly as straightforward as it should probably be. You can kind of see from the photos above, the depth of the valve itself is greater than it's separation from the tank. So you can't just unscrew it in it's current position, and it's so close to the floor that there's not much room to get a wrench in there.

I started by loosening the tank brackets and rotating the tank forward a bit to get a bit more clearance. Then it looks like I'll have to unscrew the whole "tee" assembly at least partially to get the valve around to where it might clear the tank. That's going to take a bigger wrench than what I had under the bus with me last night though, that center fitting seems in there a lot more solid than the valve / elbow was. That's all going to mean breaking a lot more connections and creating more opportunities for leaks than I was hoping, but I'm not seeing any way around it currently.

Hopefully I'll be able to make more progress this weekend.

Rob
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Old 11-04-2017, 05:08 PM   #12
Skoolie
 
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Year: 1997
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Chassis: AARE 3903
Engine: Cummins 8.3L 12v
Rated Cap: 78
Made good progress once I accepted that I just had to do what I had to do. Removing the large air lines from the end and back, I was able to rotate the tank about 90 degrees.



Then I could rotate the whole top manifold to the point where the valve could be spun off.



Then I installed the “new” valve and put it all back together.



It charged up fine after starting the engine, and brakes seem back to normal pressure drop and recovery. After stopping the engine the pressure holds as it should either with brakes released or depressed. However I can hear a slow leak still, so I’ll have to get in there with the bubbles and track it down. Can’t say I’m too surprised. But I’m back to drivable!

Thanks for all the help!

Rob


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Old 11-04-2017, 08:25 PM   #13
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Rated Cap: 7 Row Handicap
do you hear the slow leak in side the cab or outside? I had to replace the Air valve on my Seat because of a slight air hiss I kept hearing..

if outside check to see if its coming from your air dryer.. the check valves go bad in those and you'll get a hissing coming from the exhaist port on the bottom of the dryer.
-Christopher
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Old 11-04-2017, 08:57 PM   #14
Skoolie
 
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Engine: Cummins 8.3L 12v
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I only had a few minutes, but found the worst offender. I had to break 4 hose connections and 3 joints to get the valve replaced. So I wasn’t too surprised that one of my new connections was leaking. Of course it had to be the one on the back of the tank that’s hardest to get at ;). But I tightened it up and can’t hear it any more. I’ll have to check again with the engine off later to see if there are any more.

I’m assuming my check valves must be working as I hadn’t lost any pressure over night on the front or back gauges, and the valve replacement was on what I believe is the wet / accessory tank.


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Old 11-04-2017, 10:56 PM   #15
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Teflon tape is your friend.
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Old 11-06-2017, 04:12 PM   #16
Bus Crazy
 
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On the pipe thread joints, yes. Pipe thread sealant (a sticky paste), especially the stuff with teflon in it, is also nice. Don't use either of these on the compression fittings at the tube ends!
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Old 11-06-2017, 04:13 PM   #17
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Roger that.
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Old 11-06-2017, 04:19 PM   #18
Skoolie
 
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Engine: Cummins 8.3L 12v
Rated Cap: 78
Air Leak Front Drivers Side

Thanks. I’m using the yellow gas rated tape on all the threads only. Compression fittings were all already there, didn’t replace any of those. Most of the fitting are pretty old, so it’s hard to tell how much to torque them down. I did try to clean the threads quickly with a shop towel. Might have been good to clean more thoroughly with a solvent. I probably under did it a bit, then tightened down once pressurized when I can see where the leaks are.


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Old 11-06-2017, 04:32 PM   #19
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Quote:
Originally Posted by family wagon View Post
On the pipe thread joints, yes. Pipe thread sealant (a sticky paste), especially the stuff with teflon in it, is also nice. Don't use either of these on the compression fittings at the tube ends!
Second that.
Compression or flare fittings done correctly and tightened correctly might need a little more wrenching on them once pressure gets involved.
Some flare/compression fitting manufacturers actually say to use an oil compatible with what you are installing there flare or compression for on the threads of the fitting to be connected to.
If the connection is starting to sqeak before you get it to it specific torque rating of inch or feet pounds then it should have been lubricated?
For me it means if I am installing refrigerant piping then I use refrigerant oil,if I am running brake line then I use brake fluid and if I am installing air brake fittings then I would use air compressor oil.
Good luck
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Old 11-06-2017, 04:53 PM   #20
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All pipe thread tapes will tell you what they are compatible with.
In my world as a high pressure pipe fitter we use a liquid/canned joint compound as a lubricant and the tape over that as a sealant on piping connections.
Compression fitting done correctly means tubing cut a little long and jammed all the way into the fitting and tightened down are usually trouble free and that's why they were chosen for the air brake system a flare connection requires a little more attention and the correct tools. Some require single flare and some brake systems require a double flare which could mean a brake failure under load if not done properly or using the wrong tool.
Me personally I will lubricate any and everything I do and tight the pee out of it so that I know if there is a leak or problem then it is with that specific connection.
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