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General Discussion of preventative/corrective maintenance and other technical issues regarding your coach that are not covered in other Mechanic's Corner categories (ex. refrigerators, water heaters, and compressors).

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  #1  
Old 08-08-2010
Gregg Kizer's Avatar
Gregg Kizer Gregg Kizer is offline
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Default Air System Question

GROUP Question:

Started the engine after coach setting for one week (setting in driveway, from a Week ago= 400 mile round trip/air system @ 0 psi) and noticed the air system was not building up pressure as usual. Further checking, notice the cycle of air blast discharge towards the ground in the area of the air dryer unit. Of course coach is setting on the bumpers of the air bags (air bags in discharge position). Coach in this position dose not allow for easy access to the air lines, of course.

Wondering where one should start looking for some leak or air dryer unit needing to be checked. The air dryer is new, two years ago (low mile coach use since installed) and the coach has been on various short trips this year, working fine. I can not belive setting just one week from my last trip would bring the system to it's death. Maybe some animal got to one of the air lines??? System will not build up any pressure in coach (air gauge), but about every 20 seconds it will discharge big time at the air dryer unit...(this leads me to belive the engine air compresser is working and building pressure, but a big leak in air line, air dryer unit or tank system is the reason the air system is not working!!!!). Would the air dryer system unit be the problem???

Series 60 DD engine..'96 coach. never had any problem with the system and air dryer unit was replaced NEW instead of a service job on old unit (air dryer). Also at that time, new Lenyard air tank valves were installed at each air tank (3 units) to manual discharge each air tank, via remote wire at curb side of coach, as I desire.

In addition, an SMI Air Force One Brake system was installed, but the air line they installed only works upon applying the coach air brakes (check valve)for air to the toad control box unit in the JEEP toad (over 800 miles towing the toad JEEP with no problems since the install about 1st of June of this year/2010).

Any thoughts where to start???
Gregg
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Gregg Kizer KB9BG
'96 WBSD 42'(Mid Door) Body Number F116276
SMI Air Force One/2001 Jeep Grand Cherokee Limited or Tow Dolly/Chevy VOLT (electric)
Pan & Tilt rear Camera System/12 cams/Security System
New Castle, Indiana (summer)
Bradenton, Florida (winter)
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  #2  
Old 08-09-2010
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The_Money_Pit The_Money_Pit is offline
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Default

Quote:
Originally Posted by Gregg Kizer View Post
GROUP Question:

System will not build up any pressure in coach (air gauge), but about every 20 seconds it will discharge big time at the air dryer unit...(this leads me to belive the engine air compresser is working and building pressure, but a big leak in air line, air dryer unit or tank system is the reason the air system is not working!!!!). Would the air dryer system unit be the problem???

Any thoughts where to start???
Gregg

I would start at your air compressor governor.

The fact that you are not building pressure, BUT your air dryer is going through purge cycle is confusing. Sounds like the governor is not working correctly and forcing air dyer to purge when instead it should be building pressure.


Test: try airing system with aux compressor



OVERVIEW

Every truck with air brakes has an air compressor on the engine. The air compressor keeps the air tanks full, so there is always air available to stop the truck. All air has a certain level of humidity which means that there is always water vapor in the atmosphere no matter if you're in a dry or damp climate. Air is heated as it's compressed, and it cools as it travels through the discharge line to the air tank. This cooling results in condensation creating pools of water in the bottom of the truck's air tanks. You will also find oil from the compressor and any contaminants that made it through the compressors air filter in the the water.
Air dryers were created to minimize the amount of moisture and other contaminants that make it to the air tanks. The Bendix AD-9 air dryer alternates between two modes or "cycles" during use, the charge cycle and the purge cycle. Both cycles play an important part in keeping your air tanks as clean as possible.

AD-9 CHARGE CYCLE

With an AD-9 air dryer installed, contaminants enter the supply port of the air dryer end cover. As the compressed air travels through the end cover assembly, its direction of flow changes several times causing contaminants to condense and drop to the bottom of the air dryer end cover.
The compressed air exits the end cover and flows into the desiccant cartridge where it flows through an oil separator that removes any water as well as oil and solid contaminants. The air then leaves the oil separator and enters the desiccant drying column. The moist air flowing through the column of desiccant becomes progressively drier as the water vapor absorbs into the desiccant material. The desiccant cartridge removes 95% of the water vapor from the pressurized air.
Most of the dry air exits the desiccant cartridge through a built-in single check valve and fills the purge volume between the desiccant cartridge and outer shell. Some air exits the desiccant cartridge through the purge orifice near the check valve.
The dry air is then moved out of the purge volume through the single check valve and out the delivery port to the first (supply) reservoir of the air system. The air dryer stays in the charge cycle until the air brake system pressure reaches the governor cutout setting.
AD-9 PURGE CYCLE

The purge cycle of the air dryer begins when the governor causes the compressor to unload (stop compressing air). During compressor unload, the line connecting the governor unloader port to the AD-9 air dryer end cover control port is pressurized. The air pressure causes the air dryer purge valve to open. Contaminants in the end cover sump are expelled immediately when the purge valve opens. At the same time, the air that was traveling through the desiccant cartridge reverses direction and begins to flow to the open purge valve removing oil and solid contaminants collected by the oil separator.
The initial purge and desiccant cartridge decompression happens in just a few seconds and is evidenced by a burst of air at the AD-9 air dryer exhaust.
The flow of dry air through the desiccant cartridge drying bed reactivates the desiccant material by removing the water vapor it previously absorbed. It normally takes 15-30 seconds for the entire purge volume to flow through the desiccant drying bed.
The single check valve in the AD-9 end cover keeps air pressure in the brake system from blowing back into the air dryer during the purge cycle.
The purge valve will not close until air brake system pressure is reduced and the governor signals the compressor to begin compressing air again. That will start the next charge cycle.

http://www.anythingtruck.com/commerc...ad9function.mv
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Last edited by The_Money_Pit; 08-09-2010 at 12:41 AM.
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  #3  
Old 08-09-2010
Bill Pape's Avatar
Bill Pape Bill Pape is offline
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Greg,

Try to air up with an external shop air compressor
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  #4  
Old 08-09-2010
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Ernest Ekberg Ernest Ekberg is offline
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Hey Gregg, good to hear from you. You going to RATS? I believe your air governor is due for replacement. Ernie
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  #5  
Old 08-09-2010
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Just wondering, is the dump valve open, try cycling it a few times. Which guages show 0 pressure, I assume you have a front and rear brake pressure guages, and perhaps a tag pressure guage.

Try pulling the lanyard drains and see if there is pressure in all three tanks.
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  #6  
Old 08-09-2010
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Gregg Kizer Gregg Kizer is offline
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Quote:
Originally Posted by Ernest Ekberg View Post
Hey Gregg, good to hear from you. You going to RATS? I believe your air governor is due for replacement. Ernie
Hey Ernie, sounds like you are planning on the RATS this year, Hope so!!

I am like you, still working for Health Insurance...HA!!! We have attended the last few RATS outings and trying to work out the details for this year (they move the event up by one week and mess my normal days off from work, but I am still working on being there and continue on to Myrtle Beach and then on to Florida, before returning back to the cold work county. HA!!! Hope to see youi there!!!

See my othe post on my problem on the air system....

Gregg
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Gregg Kizer KB9BG
'96 WBSD 42'(Mid Door) Body Number F116276
SMI Air Force One/2001 Jeep Grand Cherokee Limited or Tow Dolly/Chevy VOLT (electric)
Pan & Tilt rear Camera System/12 cams/Security System
New Castle, Indiana (summer)
Bradenton, Florida (winter)
kb9bg@arrl.net
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  #7  
Old 08-09-2010
Gregg Kizer's Avatar
Gregg Kizer Gregg Kizer is offline
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Join Date: Jan 2008
Location: New Castle
Posts: 175
Default

Quote:
Originally Posted by gcyeaw View Post
Just wondering, is the dump valve open, try cycling it a few times. Which guages show 0 pressure, I assume you have a front and rear brake pressure guages, and perhaps a tag pressure guage.

Try pulling the lanyard drains and see if there is pressure in all three tanks.
Gardner:

Your sugestion was quick and easy upon arriving home from work late tonight, thus this was my first choice of effort. Guest What? You win... After starting engine, flipping both supen & tag air bags switches as the engine was running, the air gague started to build pressure. Could all the hot and humid weather play a part in this problem issue??

After full air build up ([of the coach I]discharge at air dryer unit[/I]), I fipped the supen air switch and brought coach up to normal level & then the tag air switch to bring tag air bags to full level. Even depressed brake peddel with all items working like designed. I even depress the brake peddel (last thing done) when leaving coach (store for period of time/setting) to take the full pressure off a little (bleed some air out of the system)

Question: I am trying to walk away with some thoughts as to what was going on (all the WHYS as what was happening & trying to learn form this situation...) and should one be carrying a spare air governor for back up parts. Trust me, I do not want to be stranded sitting as I am in my driveway out on the road and not being able to air up even to repair the problem areas (air governor or air dryer unit..

I try to do the on going maintence and not spare the $$$$, but this situation could bring some interesting bad times while enjoying the travel thing...

Henced: One needs an electric (run off gen set) air compressor unit (150 PSI) to get in by airing coach up, but wonder if anyone has done this to get in with this kind of problem. Will the electric compressor unit beable to keep up with the coach air needs to get in (off the road to a service & parts store) for the service work???

I am sure the air governor unit needs to be looked into as a service item. I need to do the research on location of the unit (series 60 DD engine) and required service routines, etc..

Any like engines owners with all their detail of addressing this particle issue of preventive maintance out there on this issue?????

Needless to say, these are thinking Man's toys, just to keep them realiable while out on the road away from home..is a big job, but FUN..HA!!!!

I guess this is why we all migrate to this web site and read alot, for some day it will be you turn in the barrel (problems) and it helps to have great group support to make you think when it is your turn in the barrel.. HA!!!

Is there any early warning signs of when an air govenor gives up? I can only envision the system giving up while running down the road.. WOW!!!

Gregg
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Gregg Kizer KB9BG
'96 WBSD 42'(Mid Door) Body Number F116276
SMI Air Force One/2001 Jeep Grand Cherokee Limited or Tow Dolly/Chevy VOLT (electric)
Pan & Tilt rear Camera System/12 cams/Security System
New Castle, Indiana (summer)
Bradenton, Florida (winter)
kb9bg@arrl.net
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  #8  
Old 08-09-2010
Gregg Kizer's Avatar
Gregg Kizer Gregg Kizer is offline
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Location: New Castle
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Quote:
Originally Posted by Bill Pape View Post
Greg,

Try to air up with an external shop air compressor
I was going to head in this direction, but try the dump switch approach first and the air system started to work as designed.

Thanks for the suggestion..
__________________
Gregg Kizer KB9BG
'96 WBSD 42'(Mid Door) Body Number F116276
SMI Air Force One/2001 Jeep Grand Cherokee Limited or Tow Dolly/Chevy VOLT (electric)
Pan & Tilt rear Camera System/12 cams/Security System
New Castle, Indiana (summer)
Bradenton, Florida (winter)
kb9bg@arrl.net
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  #9  
Old 08-09-2010
Gregg Kizer's Avatar
Gregg Kizer Gregg Kizer is offline
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Join Date: Jan 2008
Location: New Castle
Posts: 175
Default

Quote:
Originally Posted by The_Money_Pit View Post
I would start at your air compressor governor.

The fact that you are not building pressure, BUT your air dryer is going through purge cycle is confusing. Sounds like the governor is not working correctly and forcing air dyer to purge when instead it should be building pressure.


Test: try airing system with aux compressor



OVERVIEW

Every truck with air brakes has an air compressor on the engine. The air compressor keeps the air tanks full, so there is always air available to stop the truck. All air has a certain level of humidity which means that there is always water vapor in the atmosphere no matter if you're in a dry or damp climate. Air is heated as it's compressed, and it cools as it travels through the discharge line to the air tank. This cooling results in condensation creating pools of water in the bottom of the truck's air tanks. You will also find oil from the compressor and any contaminants that made it through the compressors air filter in the the water.
Air dryers were created to minimize the amount of moisture and other contaminants that make it to the air tanks. The Bendix AD-9 air dryer alternates between two modes or "cycles" during use, the charge cycle and the purge cycle. Both cycles play an important part in keeping your air tanks as clean as possible.

AD-9 CHARGE CYCLE

With an AD-9 air dryer installed, contaminants enter the supply port of the air dryer end cover. As the compressed air travels through the end cover assembly, its direction of flow changes several times causing contaminants to condense and drop to the bottom of the air dryer end cover.
The compressed air exits the end cover and flows into the desiccant cartridge where it flows through an oil separator that removes any water as well as oil and solid contaminants. The air then leaves the oil separator and enters the desiccant drying column. The moist air flowing through the column of desiccant becomes progressively drier as the water vapor absorbs into the desiccant material. The desiccant cartridge removes 95% of the water vapor from the pressurized air.
Most of the dry air exits the desiccant cartridge through a built-in single check valve and fills the purge volume between the desiccant cartridge and outer shell. Some air exits the desiccant cartridge through the purge orifice near the check valve.
The dry air is then moved out of the purge volume through the single check valve and out the delivery port to the first (supply) reservoir of the air system. The air dryer stays in the charge cycle until the air brake system pressure reaches the governor cutout setting.
AD-9 PURGE CYCLE

The purge cycle of the air dryer begins when the governor causes the compressor to unload (stop compressing air). During compressor unload, the line connecting the governor unloader port to the AD-9 air dryer end cover control port is pressurized. The air pressure causes the air dryer purge valve to open. Contaminants in the end cover sump are expelled immediately when the purge valve opens. At the same time, the air that was traveling through the desiccant cartridge reverses direction and begins to flow to the open purge valve removing oil and solid contaminants collected by the oil separator.
The initial purge and desiccant cartridge decompression happens in just a few seconds and is evidenced by a burst of air at the AD-9 air dryer exhaust.
The flow of dry air through the desiccant cartridge drying bed reactivates the desiccant material by removing the water vapor it previously absorbed. It normally takes 15-30 seconds for the entire purge volume to flow through the desiccant drying bed.
The single check valve in the AD-9 end cover keeps air pressure in the brake system from blowing back into the air dryer during the purge cycle.
The purge valve will not close until air brake system pressure is reduced and the governor signals the compressor to begin compressing air again. That will start the next charge cycle.

http://www.anythingtruck.com/commerc...ad9function.mv
Great informatio and I will start on many of these items in regards to the air govenor unit and all other items in you suggestions.

Many thinks for the GREAT post!!

I will keep testing the Air System (hot & humid weather conditions, etc.) to try to come up with some reason as to what was going on.

I am like you, the air dryer is going through purge cycle is confusing. Sounds like the governor is not working correctly and forcing air dyer to purge when instead it should be building pressure. O'well, just love those intermintten type problems!! HA!!!

We all need some sort of realiable of our units when shutting them off and down, with the need to turn the key and start the air up process. (See other repy post on other thoughts on this issue!!).

I'll start the coach tomorrow night and will see what happens!!

Thanks for all the suggestions..
__________________
Gregg Kizer KB9BG
'96 WBSD 42'(Mid Door) Body Number F116276
SMI Air Force One/2001 Jeep Grand Cherokee Limited or Tow Dolly/Chevy VOLT (electric)
Pan & Tilt rear Camera System/12 cams/Security System
New Castle, Indiana (summer)
Bradenton, Florida (winter)
kb9bg@arrl.net
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  #10  
Old 08-09-2010
gcyeaw's Avatar
gcyeaw gcyeaw is offline
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Gregg,
Glad I could help. It just seemed that with the spitter valve operating, the governor was doing it's thing, so there must have been pressure in the system. Anyway, good to hear you are on the road again. I always like it when the fix is easy, but I also don't like it when I am not sure what the original cause was.

On my FC it requires pressure to activate the dump valves, so if the system fails the default is aired up. I would guess yours is the same. So for some reason the dump valve may have been stuck.
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86 PT-36 Golden Memories
83FC35 SB $IXTEEN TON$ SOLD
78 FC 33 Happinest (Sold)
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