Air Pressure won't build

Topic: Air Pressure won't build (Read 2625 times) previous topic - next topic

Re: Air Pressure won't build

Reply #25 – January 03, 2023, 03:16:41 pm

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 .

Re: Air Pressure won't build

Reply #26 – January 03, 2023, 03:48:26 pm

Quote from: Protech Racing – January 03, 2023, 03:16:41 pm

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!

Re: Air Pressure won't build

Reply #27 – January 03, 2023, 04:25:51 pm

Quote from: Chuck & Jeannie – January 03, 2023, 03:48:26 pm

Quote from: Protech Racing – January 03, 2023, 03:16:41 pm
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

Re: Air Pressure won't build

Reply #28 – January 03, 2023, 08:58:00 pm

Based on drawing Michelle posted, putting air in at air hose fitting will not air up brake air tanks.

Re: Air Pressure won't build

Reply #29 – January 04, 2023, 03:34:31 pm

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?

Re: Air Pressure won't build

Reply #30 – January 04, 2023, 03:53:32 pm

You can get a governor from NAPA for 20 bucks. I paid 17.00 a couple years ago.

Re: Air Pressure won't build

Reply #31 – January 04, 2023, 04:01:56 pm

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.

Re: Air Pressure won't build

Reply #32 – January 04, 2023, 04:52:28 pm

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

Re: Air Pressure won't build

Reply #33 – January 04, 2023, 05:29:53 pm

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.

Re: Air Pressure won't build

Reply #34 – January 04, 2023, 05:32:00 pm

Quote from: dkeener – January 04, 2023, 04:01:56 pm

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.

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.

Re: Air Pressure won't build

Reply #35 – January 04, 2023, 05:39:37 pm

Quote from: dkeener – January 04, 2023, 03:34:31 pm

Can anyone tell me where the air dryer is located on a 2003 U270?

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?

Re: Air Pressure won't build

Reply #36 – January 04, 2023, 05:50:26 pm

Just for kicks and giggles, can you open the purge valves near the driver front wheel and see if any white powder comes out...

Re: Air Pressure won't build

Reply #37 – January 05, 2023, 12:34:22 pm

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.

Re: Air Pressure won't build

Reply #38 – January 05, 2023, 12:56:37 pm

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.

Re: Air Pressure won't build

Reply #39 – January 05, 2023, 01:41:02 pm

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.

Re: Air Pressure won't build

Reply #40 – January 05, 2023, 02:09:26 pm

If that hose is metal and runs to the compressor it's the one I told you about from the beginning.

Re: Air Pressure won't build

Reply #41 – January 05, 2023, 02:24:01 pm

Quote from: dkeener – January 05, 2023, 01:41:02 pm

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.

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.

Re: Air Pressure won't build

Reply #42 – January 05, 2023, 02:32:44 pm

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.

Re: Air Pressure won't build

Reply #43 – January 05, 2023, 02:57:55 pm

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.

Re: Air Pressure won't build

Reply #44 – January 05, 2023, 03:08:55 pm

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.

Re: Air Pressure won't build

Reply #45 – January 05, 2023, 03:12:57 pm

Quote from: Elliott – January 05, 2023, 03:08:55 pm

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

Re: Air Pressure won't build

Reply #46 – January 05, 2023, 03:18:25 pm

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

DQ6026 - General Service Kit - Haldex product

Quote from: dsd – January 02, 2023, 10:48:57 pm

Erratic pressure indication can be just the pressure sensor getting old also
https://www.summitracing.com/parts/SWW-82894

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

Re: Air Pressure won't build

Reply #47 – January 05, 2023, 06:21:00 pm

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.

Re: Air Pressure won't build

Reply #48 – January 06, 2023, 10:03:10 am

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.

Re: Air Pressure won't build

Reply #49 – January 06, 2023, 11:01:12 am

Quote from: ClassAClassy – January 05, 2023, 06:21:00 pm

...he clamped a hose under our rig (below the driver side gas pedal, see photo)

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.

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