Started the coach in the barn where it has been all winter, except for a couple trips around the block, the air pressure built up as usual. Drove the coach over to the house and parked it overnight for use as a porta potty and shower due to plumbing issues in the main house over new years. Started the coach the next day after home plumbing issues resolved and drove it back to the barn, 300 feet.
Got it in the barn but not all the way, so went to check to see how much more to pull in, a tight fit needless to say. By the time I got back in to pull forward the air pressure warning was beeping and the gauges were reading in the 20's. Would jump up to about 40 then drop down to 20. So the air brakes are locked due to low air pressure. Any thoughts how this could have happened overnight? Temps in the mid-60's at night and mid-70's in the day.
Could be a major air leak. When you say jump up to 40 lbs. jump do you mean it goes up to
40 lbs. immediately.
Locate the D2 air governor back near the engine and give it a couple love taps if no other major air leaks are found.
Leaking from one of a dozen places. Your going to have to listen from the back of the bus with engine hatch up. Let some one else raise rpm a bit while you are standing at the rear. That bad of a leak won't require spray soap, you will be able to hear it. Have them release the brakes or you can get it built up enough to release them. You will likely have to listen fast and repeat it. SCOTCH the tires for safety.
Building to 40 quickly makes me think d2 is working but if no leak is found then d2.
I don't think an air leak as the air bags are staying up, unless there is some kind of backflow valve or they are separate systems. Can't hear any air leak while shut down and no way to hear anything with engine on and in the barn. Will try some love taps on he D2, if I can find it.
Upon engine start the pressure goes to about 20 then jumps to 40 and falls back to 20 almost immediately. Revving engine has no effect, just continues the above cycle.
1. As Doug says, possible sticky D2 governor. If percussion doesn't help, you can also try turning the adjusting screw on the top of the governor in and/or out to see if it frees up the internal plunger, as follows:
A. Remove the top cover from the governor.
B. Loosen the adjusting screw locknut.
C. To raise the pressure settings, turn the adjusting screw counter-clockwise. To lower the pressure settings, turn the adjusting screw clockwise. Note: Be careful not to over adjust. Each 1/4 turn of the adjusting screw raises or lowers the pressure setting approximately 4 psi.
D. When proper adjustment is obtained, tighten the adjusting screw locknut and replace the cover.
https://n0c357rmy1njbuit2friqwu.blob.core.windows.net/documents/BrddZ4M0I0EBhB_SD-01-503_US_005.pdf
Air bags get air from secondary tank, your leaking from the wet tank supply which supplies air to brakes.
There will be a stainless air line running from the d2 to the drier, may be tucked in behind rear frame rail standing facing the engine. That's where I would start.
If it's the stainless line you can hear it with the engine running standing near it. If that's it say so and there's a way to patch it to get it in the barn. Getting ahead of ourselves maybe but it's where I would look first. It will leak with the park brakes set or released.
The line runs from the compressor to the drier, nor from d2.
When was the last time the air dryer was serviced?
Purge valve is open and won't close?
Have to look at service records for dryer service. Probably 3-4 years I'm guessing. Haven't driven much in that time. Would the dryer stop working that quickly? Will purge valve open by itself?
Dryer cartridge should be changed annually and dryer rebuilt or replaced every 3-4 years. Purge valve is constantly opening and closing as it reaches pressure and then when it drops to build pressure
I had my air dryer go a year ago and I couldn't move. Reach under your air dyer with the engine
running and if you have air pouring out of the bottom of the dryer that would be your problem.
I thought about that as soon as I read your post but the air pressure going up and down I through
me as I have never seen that.
Erratic pressure indication can be just the pressure sensor getting old also
https://www.summitracing.com/parts/SWW-82894
Can I check for air leaks by hooking up my barn air compressor to the coach via the compressor line in the bay with the fuel tank and propane tank? Also won't this give me the pressure needed to release the brakes? When I had the coach towed once the wrecker ran a line from his truck to this connection or was this just for the suspension since he had already pulled the rear axle and the front was lifted off the ground?
1. Yes
2. same as #1 yes As long as the compressor can keep up with the leak.
Mike
Don't forget the possibility of a "blue box" failure (since it's a 2002):
Air pressure sending unit where do they ground at? (https://www.foreforums.com/index.php?topic=30619.msg266090#msg266090)
02 U320 Air gauge stopped working (https://www.foreforums.com/index.php?topic=37921.0)
Intermittent gauges (https://www.foreforums.com/index.php?topic=42753.0)
On my 2014 when I connected air compressor to the air fitting in my compartment it supplied air to the HWH tanks (2) but did not fill the wet, front or rear tanks.
After hearing the symptoms I would have bet money on the steel supply line, or like mentioned possibly the pop off valve under the drier not closing. We all may learn something here. BE SURE and post what the culprit turns out being. Dozens of places for an air leak but not so many leaking that volume of air. Did you listen at the rear of the bus with hatch open and engine running??
I'm anxious to find a he culprit as well. However just coming off shoulder surgery so pretty limited in what I can do and maneuverability. I did get the fittings to connect the barn air compressor to the coach to listen for leaks after I love tap the governor.
Has been wonderful hearing all the helpful suggestions so keep them coming.
You will be able to hear a leak that big over the noise of the engine. It would have to be huge. My money is on the governor or air dryer preventing air flow. Or the compressor itself.
At this point the low hanging fruit is to just replace the governor. It's easy, cheap, and something worth doing after enough time has gone by anyways.
You need some help over there having new shoulder surgery. Don't need to be doing this work. Same thing here.
My bet is dryer fault. Any open line or fitting will be a linear leak without building pressure. Running a long line from the shop to the tow air fitting will aid in hearing the leak for sure.
The dryer may be protected by one or 3 check valves and may not leak unless the engine is running .
Excellent point! Which is why consulting the air system schematic is so important!
My PDF is too large a file for the forum, but here's a screenshot of a 2003 air schematic (ignore the tag axle bits for a non-tag coach) and I managed to convert it to a forum-friendly PDF
Based on drawing Michelle posted, putting air in at air hose fitting will not air up brake air tanks.
Well tapped on the governor and still no air. Called Nacogdoches and the governor is $86 + shipping for part number RKN 18532. Still can't hear any air leaks , but not sure it is making enough air to hear a leak, so may start with changing the governor, then move to the air dryer. Can anyone tell me where the air dryer is located on a 2003 U270?
You can get a governor from NAPA for 20 bucks. I paid 17.00 a couple years ago.
Do you have a Cummins ISL400 in your coach? I have a 2003 U270 and wondering if we have different motors thus different compressors and governors.
My coach is 7 years older than yours but the d2 should be very similar. I think Doug showed a picture of one earlier in your thread. Reply #2
There are instructions on how to bypass the drier here on the forum.
When the turbo boost saver valve failed in my drier it couldn't build air pressure.
If you're asking because of the price difference (FOT's $86 plus shipping vs. a NAPA $20 one), they're the same thing. There's nothing special about getting one from FOT, other than the markup.
A quick search of the forum for D2 governor should bring up what you need to know about low/high pressure settings, etc.
On a U320 of that year (ISM450), it's near the lower rear frame member, biased to driver's side. An ISL400 is likely close to the same.
DA33100X is the Haldex factory-reman'd part number. You'll need some fittings and the heater from the old one, so pay the core charge then take the old one back after you're done to get the core charge refunded.
Getting pressure high enough to drive? (https://www.foreforums.com/index.php?topic=38335.msg372969#msg372969)
Just for kicks and giggles, can you open the purge valves near the driver front wheel and see if any white powder comes out...
No white powder coming out from the air discharges by the front wheel. Couldn't crawl under the coach for the tanks.
Friend helped me change the governor and listen for air leaks. We found air exiting from the large hose coming out from the bottom of the air dryer. I did not notice if this was coming out before the change or not. Also the air dryer canister and my records shows the dryer was serviced in 2015 (my how time flies and memory just cant keep up!)
So I guess the next task is to change the air dryer with a kit. Some have mentioned that the air dryer could stop air going to the system.
The air dryer is the first place air goes after leaving the air compressor. If the large hose you mention is connected to the purge valve on the bottom of the dryer, then you have found your leak.
A dryer as old as yours is WAY overdue for replacement. I would recommend a complete factory rebuilt unit rather than a filter cartridge kit. NAPA stores are a good place to find rebuilt dryers.
Thanks for that. I was considering just the kit that was put in at FOT but have seen a few posts also recommending/replacing the whole air drier unit. So back to the store I go.
If that hose is metal and runs to the compressor it's the one I told you about from the beginning.
That kit is just the desiccant cartridge and maybe one or two other things.
If this is the original air dryer, it would be wise to do the reman'd unit referenced above. Also, don't go cheap and buy a unit that was rebuilt from other than Haldex.
Just a note in case, these air system parts on your coach are not motor home exclusive. All trucks that have air systems use the same so these parts can be found at Napa sometimes or ANY truck parts such as Freightliner, KW and so on. Might save you some money because you have sources and options.
As others has said, your best option is a factory (as in the factory that made it, NOT a cheap copy sold as "replaces XXX".
That gets you not only new filters, but also valves, heater, etc.
Just pull the numbers off the old one so you get the correct one.
Also, if you buy it locally they'll probably want the old one as a core. Don't turn it in until AFTER the new one is installed. It's too easy to forget to remove a fitting and it's nice to see how those fittings were configured on the old unit before installing the new one.
To add to this its may be easier to loosen fitting before it is removed unless you have a way to hold
Quote from: craneman - 3 years ago
These are the 2 kits I used, seems complete except for heater.
DQ6020 - Lower Housing Repair Kit - Haldex product (https://www.haldex.com/en/na/air-dryerair-line/air-dryers/haldex-newremanufactured/pure-air-plus-service-kits/dq6020/)
DQ6026 - General Service Kit - Haldex product (https://www.haldex.com/en/na/air-dryerair-line/air-dryers/haldex-newremanufactured/pure-air-plus-service-kits/dq6026/)
There is a lot to these kits but I personally would recommend getting a rebuilt. Resolves any heater issues and corrosion problems. Napa either has or will get one for you. Mine has worked flawlessly
Scott
Same thing happened to us with our 1991 diesel U280. Worked fine until the mechanic brought our rig out to us and shut it down. We started up the engine (started just fine) but the air pressure stayed at 0. Couldn't figure out what happened ...
The repair guy was stumped. After a few days he found a solution: he clamped a hose under our rig (below the driver side gas pedal, see photo) which allowed the air pressure to build up. When he released the clamp, we could put it into gear and go. It hasn't happened since, but we keep the clamp with us at all times, just in case.
NOTE: in our case the lack of air pressure wasn't caused by a faulty air governor; we had just had the air governor replaced due to the fact that the air pressure kept rising while driving but not lowering when the brake was pushed.
I rebuilt mine last year and the part that let go is tricky to do. I used both kits. A rebuilt one would
be easier.
Welcome to the Forum with your first post!
The photos in your post don't match your description - "below the gas pedal" - perhaps you clicked on the wrong ones?
That pressure regulator in your photos looks ready for replacement. You can buy a replacement regulator at Lowes or HD or anyplace that sells air compressor accessories. If you do install a new one, it should be set for about 60-70 PSI.
Does anyone know if the spin on dryer cartridge from the DQ6026 kit is available separately?
Keith,
Yes. If you want both filters (desiccant & coalescing) you need the DQ6036 (your best option) now if you want just the desiccant filter alone I think you will need the DQ6028. They do make a mac daddy desiccant one that is a DQ33125.
Mike
Do you know why thread these have v?
I think that mine needs. 39 1.50
Thanks
WABCO 4329012482 specs - Google Search (https://www.google.com/search?q=WABCO+4329012482+specs&oq=WABCO+4329012482++specs&aqs=chrome..69i57j0i546j0i30i546i625j0i546l2.3526j0j15&sourceid=chrome&ie=UTF-8)
39x 1.5 it is.
Well it is fixed. A new remanufactured air dryer unit fixed the problem and pressure built as usual. Now I just need to adjust the new governor for correct air pressure. Should that be around 125 on the high side?
A most gracious thank you to all who contributed to the success and hand holding throughout.
Yes - 125 would be perfect.
Anywhere in the 120-130 range is fine. Never allow the pressure to exceed 150psi. Your wet tank should have a safety pressure relief valve that will open at 150psi. It will definitely get your attention if you ever hear it open. Don't ask how I know...
How do you know...
I said don't ask...
One of those embarrassing times when you shoot yourself in the foot.
Most of the story is in the link below. In that post, I said "I assume the relief valve went into action..." Well, I was being evasive- in fact I know it went into action because it was making a extremely LOUD whistling noise that was very evident even over the running engine noise. As soon as I closed the needle valve (and the dryer purged) the sound mercifully stopped. I can only imagine what it would sound like if the engine was off and it opened while standing in close proximity to the tank. Definitely something to be avoided.
Driving Tip: Scan Your Gauges! (https://www.foreforums.com/index.php?topic=22657)
Ive had the unloader valve get stuck open one time. Now it is stuck closed and purging the dryer every 30 secs. So. Keep an eye there if you have a non air build.
I have experienced the large stainless braided line (supply line) clogged frome carbon from a well used compressor to cause this also.
Basically lack of volume that low of pressure any item would consume 20psi. D2 is a common problem cheap truck pro or fleet pride sell them cheap. I replaced mine last year and it was preset to 135psi. Truck pro 38 bucks.