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Topic: Air dryer purging even though coach has sat for a few days (Read 816 times) previous topic - next topic

Air dryer purging even though coach has sat for a few days

This is our first DP purchased in August, so this is all new to me. Based on what I've read here in the forum I think my question is about the air dryer. Correct me if I'm wrong.

Today, quite unexpectedly, I heard a long blast of air. It seemed like it was forever but it was probably more like 3 to 5 seconds. Much longer than I had ever heard it before. The coach has not been run for a few days. The air pressure gauge on the dash indicated about 30 psi.

Is this normal for the air dryer to release air like that?

While I'm asking about the air dryer. IIRC, shouldn't the air lines be bled manually somewhere inside a wheel well, or does the air dryer take care of this for me?

thanks
Ed
Ed and Michele
2000 U295  36'  (Build #5600)
8.3 ISC 350HP.
2012 Jeep Grand Cherokee (Toad)
2001 Lance Truck Camper (Sold)
2001 Lazy Daze (Class C). RK Floor Plan (Sold)

Re: Air dryer purging even though coach has sat for a few days

Reply #1 –
I too have heard a long release after parking, hours later, not days.

As to the tank drains.  On my 98 U295, 36':

There are two valves to twist, under the front end, behind the license plate, for the front and rear, "dry" tanks.
There is a valve behind the driver rear wheel, for the "wet" tank.

My understanding is the dryer catches any moisture, shooting it out, when it releases.  But any thing getting past the dryer, is caught in the "wet" tank, before going else where on the coach.

Dave Cobb
Buckhorn Lake Resort The Club, #6202, Kerrville TX
check the map.  I do rent it out when I am traveling!
2001, U320, 36' #5887, in Kerrville, FT Club #17006, (7/23 to present)
2024 Jeep Grand Cherokee L, Summit, white
EX: 98 U295, 36' #5219, (mid door), (4/13-10/23)
EX: 93 U225, 36' (4/11 to 4/13)

Re: Air dryer purging even though coach has sat for a few days

Reply #2 –
Are you sure it was the air dryer and not the leveling system letting air out to re-level?

Re: Air dryer purging even though coach has sat for a few days

Reply #3 –
I have not heard my coach do that, just the short blast when the air compressor cuts out when the engine is running.  Some water and oil get past the air dryer and into the wet tank and even into the other tanks, but mainly the wet tank.  This is especially true if the air dryer canister has never been replaced or recently.  I'm not sure when it should be replaced or whether it is done on age or miles.  The whole purpose of the air dryer is to prevent water from getting into the brake lines during freezing weather and cause a loss of braking.  The compressor gets its air from the engine intake manifold, so it is filtered air.
Jerry Whiteaker former owner 96 U270  36' #4831 Austin,TX-Owner Mods LCD TV w/front cabinet rebuild - LCD TV bedroom - Dual Central AC, either can cool coach w 30 amp - Skylights at roof AC openings - Drop ceiling for ducting of AC - Shower skylight white gelcoat/wood/epoxy frame - Air Springs/Shocks replaced - 2014 CRV - 8K Home Solar - Chevy Volt

Re: Air dryer purging even though coach has sat for a few days

Reply #4 –
Quote from: Dave and Dolly Cobb –

As to the tank drains.  On my 98 U295, 36':

There are two valves to twist, under the front end, behind the license plate, for the front and rear, "dry" tanks.
There is a valve behind the driver rear wheel, for the "wet" tank.


I have a 2000 model.  Found the one in the rear wheel well but no joy on the front. Since I just found out I don't have a license plate holder on the front I'm not sure where to look for the valve. :facepalm:

I bled the rear one and a little oil blew out, not much.

Ed
Ed and Michele
2000 U295  36'  (Build #5600)
8.3 ISC 350HP.
2012 Jeep Grand Cherokee (Toad)
2001 Lance Truck Camper (Sold)
2001 Lazy Daze (Class C). RK Floor Plan (Sold)

Re: Air dryer purging even though coach has sat for a few days

Reply #5 –
Air dryers should be service/replaced about every three years.  Perhaps 4 years in the desert SW.

The REAL issue with dryer failure is if the desiccant pack denigrates and gets into the air system.

Suggest either OE (like Haldex, Bendix, etc) parts, reman or new.  NOT overseas knockoffs.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Air dryer purging even though coach has sat for a few days

Reply #6 –
I have 4 air tanks.  One in the rear with a valve near the left rear tire and three in the front with the valve on the bottom of the tank.  I have to crawl under the coach to drain them.  Have not yet put on an extension for the drain valves to make them more easy to access.

Rich
Rich and Peggy Bowman
2002 U270 3610 WTFS, build #5939--"Freedom"
2022 Jeep Grand Cherokee Summit 4xe
SMI AirForceOne brake system
PakCanoe 15

Re: Air dryer purging even though coach has sat for a few days

Reply #7 –
Quote from: Lance Camper –


Is this normal for the air dryer to release air like that?

Ed

Not without the engine running. Bob has it correct that must have been the leveling system adjusting. If you have an air leak in the leveling system the coach will go out of level after a time, how long depends on the size of the leak. The HWH leveling system will try to level the coach by letting air out of the bags on the high side, that is what I believe you heard.

Roland
1993 U280 4341
2010 Jeep Liberty
The Pied Pipers

Re: Air dryer purging even though coach has sat for a few days

Reply #8 –
I think it's the leveling system as mine does it.  When the system wakes up to sense level if it detects an out of level condition it will exhaust air to level.  It will sound like the purge valve.

Keith
Keith, Joyce & Smokey the Australian Cattle Dog
1995 U320 SE Extreme 40' WTBI Build # 4780, with a Honda CR-V hopefully still following behind.
Motorcade # 17030
FMCA # F422159

Re: Air dryer purging even though coach has sat for a few days

Reply #9 –
Mine does the same after parked for a few hours it will exhaust and its the leveling system. I am usually parked for long periods of time so it only does it after I move and set up. After that the aux compressor runs every few days and levels. In 2 years I have only had to repleace one item the water heater. I have done extensive upgrades and one of these days will make a lsit. 60 to 70 hours a week working does not allow for much coach improvements. Looking forward to hanging it up and letting the younger crowd deal with the oil and gas conglomerate in a few years.
Adam Byler
1999 U320 M4200 DGFE Build #5389
2014 Sundowner 26 ft Enclosed
2015 Ford F150 King Ranch crew cab

Re: Air dryer purging even though coach has sat for a few days

Reply #10 –
My bet is also the leveling system making adjustments. It does not necessarily mean you have a leak. When its on auto level just the sun hitting the air bags on one side of the coach can increase the air pressure in the air bags on that side. This can trigger the leveling system to re-level the coach by letting air out of the "Hot Side".
The selected media item is not currently available.Kent Speers
Locust Grove, OK
1993 U300 SSE 40' (Restored at FOT 2009) Build 4323
720 watts Solar
6V92TA DDEC Silver Engine
2014 Subaru Outback

Re: Air dryer purging even though coach has sat for a few days

Reply #11 –
Quote from: Kent Speers –
My bet is also the leveling system making adjustments. It does not necessarily mean you have a leak. When its on auto level just the sun hitting the air bags on one side of the coach can increase the air pressure in the air bags on that side. This can trigger the leveling system to re-level the coach by letting air out of the "Hot Side".

It did happen yesterday when the temps reached into the 70's. Hard to believe when we woke up to temps in the 20's this morning. As I mentioned it was much longer in duration than I have ever heard the air dryer release air.

Ed
Ed and Michele
2000 U295  36'  (Build #5600)
8.3 ISC 350HP.
2012 Jeep Grand Cherokee (Toad)
2001 Lance Truck Camper (Sold)
2001 Lazy Daze (Class C). RK Floor Plan (Sold)

Re: Air dryer purging even though coach has sat for a few days

Reply #12 –
If it is a Haldex Pure Air Plus dryer the manual says it will expel a large volume of air ,followed by a slow flow of air lasting approximately thirty seconds.

Mark
The selected media item is not currently available.
Mark and Tanya
Milton , Florida
US Navy Veteran (DV)
1999 U270 Special 40' CAI , 2015 Jeep Wrangler Sahara

Re: Air dryer purging even though coach has sat for a few days

Reply #13 –
Yah Mark, but you have a U285. You're special.
The selected media item is not currently available.Kent Speers
Locust Grove, OK
1993 U300 SSE 40' (Restored at FOT 2009) Build 4323
720 watts Solar
6V92TA DDEC Silver Engine
2014 Subaru Outback

Re: Air dryer purging even though coach has sat for a few days

Reply #14 –
Kent , it is a U285 in name only though. Don't be hatein on me brother. :)
Hope to see you in Tuscon.

Mark
The selected media item is not currently available.
Mark and Tanya
Milton , Florida
US Navy Veteran (DV)
1999 U270 Special 40' CAI , 2015 Jeep Wrangler Sahara

Re: Air dryer purging even though coach has sat for a few days

Reply #15 –
That ain't hatein brother. Just Jokin.

Just so everyone knows that's my weird sense of humor. Mark and Tanya are good friends we met from here on the Forum. What a great group.
The selected media item is not currently available.Kent Speers
Locust Grove, OK
1993 U300 SSE 40' (Restored at FOT 2009) Build 4323
720 watts Solar
6V92TA DDEC Silver Engine
2014 Subaru Outback

Re: Air dryer purging even though coach has sat for a few days

Reply #16 –
I know you were Kent. You are a treasured friend indeed.

Mark
The selected media item is not currently available.
Mark and Tanya
Milton , Florida
US Navy Veteran (DV)
1999 U270 Special 40' CAI , 2015 Jeep Wrangler Sahara