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Topic: Air Pressure won't build (Read 3268 times) previous topic - next topic

Re: Air Pressure won't build

Reply #20 –
Quote from: dkeener –
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?

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.

Re: Air Pressure won't build

Reply #21 –
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?? 

Re: Air Pressure won't build

Reply #22 –
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.

Re: Air Pressure won't build

Reply #23 –
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.

Re: Air Pressure won't build

Reply #24 –
You need some help over there having new shoulder surgery. Don't need to be doing this work. Same thing here.

Re: Air Pressure won't build

Reply #25 –
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 #27 –
Quote from: Chuck & Jeannie –
Quote from: Protech Racing –
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 –
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 –
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 –
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 –
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 –
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 –
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 –
Quote from: dkeener –
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 –
Quote from: dkeener –
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 –
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 –
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 –
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 –
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.