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Air Pressure build slowly
First trip out in a while, and the air pressure builds real slow.  It will make it to 120psi from 20psi in about 10 minutes.  Useing the brakes in the RV park to back in will cause the Air guage to fall below 60psi and spring brake will kick in. ...

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Re: Air Pressure build slowly
Reply #1
Have someone listen for air leaks while you are applying the brakes. What you are describing is a leak after the treadle valve.

  • Dub
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Re: Air Pressure build slowly
Reply #2
Since you hear no obvious air leaks I would replace the D2 governor about 17.00 Always carry a spare if you don't already.. Air compressor last cheap part first. In conjunction to what Chuck said.

Re: Air Pressure build slowly
Reply #3
Or you could have a leak in one of the cans. If it's in the back, you would never hear it with the engine running. Pustefix Amazon.com: Pustefix Premium Bubbles Refill 8.3 fl.0z.: Toys & Games solution sprayed on with a Dollar Tree spray bottle...

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  • Dub
  • [*][*][*][*][*]
Re: Air Pressure build slowly
Reply #4
Like P said.. a canister won't blow air until you mash the brake. Get someone to listen for you.

Re: Air Pressure build slowly
Reply #5
We had the same issue you described, recently. Taking Foreforum advice....

We listened but didn't hear any leaks.
Replaced the D2 with no change.
Replaced the air hose from the compressor to the air dryer, no change.
Replaced the compressor, all...

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Re: Air Pressure build slowly
Reply #6
Yes, ASSUME you have a leak "downstream" of the brake pedal. Run engine at 1,100 RPM or so to build pressure to cut out PSI.  Turn off engine.  Have someone step on the brake pedal while you do a "walk around/crawl around and listen".

But, it that...

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Re: Air Pressure build slowly
Reply #7

When I was coming back from New Mexico last year, it took a long time to build the air. I changed the air dryer cartridge and now she comes up to pressure quickly. My next move would have been the D2, but it was new the year before. The air dryer...

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Re: Air Pressure build slowly
Reply #8
Thanks for all of the responses.
I made this topic at least 4 hrs ago, and I still have the 30psi from 2 days ago.  I  want to know why the air pressure builds up so slowly.  It has never took so long to get to 120psi.  Once at 120psi in the past,...

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Re: Air Pressure build slowly
Reply #9
This last test you did eliminated the brake system from your problem. Now you have the air compressor, line from the air compressor to the dryer and the dryer itself as the problem. The line from the compressor to the dryer will only have air...

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Re: Air Pressure build slowly
Reply #10
is this black Haldex filter the air dryer cartridge ya'll are talking about?

Buy one at O'Reilys?

Pat and Thanks a lot

Re: Air Pressure build slowly
Reply #11
Yes, that is the filter.  But, from the looks of the dryer itself, it (valves and heater) have not been serviced in a long time.

Again, a Factory (i.e. Haldex) reman replaces not just filters, but valves, heater, etc.  Basically only the metal...

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Re: Air Pressure build slowly
Reply #12
Brett, your thinking replace the whole thing that the filter is screwed onto?

what is a number and where do I get one?

I am out of town now.

Pat

Re: Air Pressure build slowly
Reply #13
Pat,

Yes, "the whole thing" would be replaced by a reman Haldex dryer.

There will be a PN on the dryer itself.  Most any parts house that deals with OTR trucks will have the reman units in stock.

Again, think of this as preventive maintenance.  As...

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Re: Air Pressure build slowly
Reply #14
When my air dryer went bad after sitting in storage, I could get to 30 PSI and no more. Replaced the dryer assembly, like Brett said, worked perfect till coming back from NM. It would slooooowwwwly build air pressure to 110-120 and hold no...

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Re: Air Pressure build slowly
Reply #15
I get them at NAPA part number DA33100X Haldex

Re: Air Pressure build slowly
Reply #16
Thanks Red for that part number and source.

pat,

Re: Air Pressure build slowly
Reply #17
When you unscrew the filter, spray the basin with WD 40 or ATF and toothbrush out the goo that settles at the purge port.

Re: Air Pressure build slowly
Reply #18
Hi Mike,
  I have made it to Gunsmoke Rv Park, Dodge City Kansas.  Going down the road, no problem, gauge stays at 110-120psi.  Going to try for home in the morning.  I will do as Brett suggested and change the whole air dryer.  i will update when...

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Re: Air Pressure build slowly
Reply #19
I made it home with no problems, other that a patio awning deploy at 60MPH.  I replaced the air dryer today with a napa da33100x.  It is the same a my old one.  I had to change 3 fittings from old to new.  Hooked up the heater.  I can tell no...

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Re: Air Pressure build slowly
Reply #20
60 psi to 110 psi is fairly fast but 0 to 60 psi takes about 4 or 5 minutes on ours. Windex is not good for bubbles. You need a soapy mixture so bubbles will show leaks. Lots of places for a leak to be so it takes time to find the leak. Any water...

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  • oldguy
  • [*][*][*][*][*]
Re: Air Pressure build slowly
Reply #21
I use a product called Super Miracle Bubbles which is a bubble maker for kids to make bubbles. 

Re: Air Pressure build slowly
Reply #22
I will look more tomorrow with dish soap and water.  I was check my work today on the install of the air dryer.  BTW the napa dryer was $275 with exchange of old unit.

Pierce are you talking about idle RPM(,ine is 700) on the 0-60psi ???

Pat

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Re: Air Pressure build slowly
Reply #23
I usually build air at about 900-1000 rpm. Idle is 600.

P

Re: Air Pressure build slowly
Reply #24
Pat,

Gauge falls to 60 psi after 4 hrs. This indicates a pretty good-sized leak, as your only air is the brakes, air horn and "tire fill hose", not the complex suspension of other coaches.

Be sure to check the gate valve to the hose to fill tires....

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