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Topic: 1991 40’ GV unihome Air tank drain (Read 553 times) previous topic - next topic

1991 40’ GV unihome Air tank drain

Had an  air shock blow on the rear drivers side, front bag.  Removed fender, got stubby jack in place, replaced bag.  Not that bad of a job, couple of oak blocks assisted with support next to jack.  75, and still learning to do things.
While doing it, found a petcock Low down, on the wall between utilities and rear tire.  Traced it back to the bottom of the reserve air tank.  Opened it up, and drained gallons of water before getting to air!  No wonder the on board compressor was cycling on too often— the tank air capacity was near nothing! 

Re: 1991 40’ GV unihome Air tank drain

Reply #1 –
Steve,

Welcome to the ForeForum.

Glad you got your AIR BAG replaced.  What condition are the others in?

And, water in the wet tank indicates a failed AIR DRYER.  Best advice is to go with a factory (i.e. the factory that made it, not "someone else made one to replace and we have no idea what quality) air dryer.
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: 1991 40’ GV unihome Air tank drain

Reply #2 –
Quote from: StevesRV –
Traced it back to the bottom of the reserve air tank.  Opened it up, and drained gallons of water before getting to air!
Welcome to the Forum.  Always glad to have new GV owners!

If you are gonna hang out here, you might as well learn the lingo.  Makes it easier if everyone uses the same technical terms.

Specifically, what you called the "reserve" tank is, on Foretravel coaches, more properly named the "wet" tank...which in your case is an apt description.

Like Brett says, a new or factory rebuilt air dryer is in your immediate future.  The local NAPA store is a good place to find what you need, but you will have to tell them what model dryer you have.

If you can post a photo of your dryer we can probably tell you the model number.
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: 1991 40’ GV unihome Air tank drain

Reply #3 –
Steve,

How about including all your information so we know what model coach, year, etc? Makes it easier to answer your questions.

Welcome again.

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: 1991 40’ GV unihome Air tank drain

Reply #4 –
There are also 2 air tanks up front near the front axle. They also have drains on the bottom of the tank. Probably need to drain those as well. Since I have a 1990 I can get you pictures but not till Monday. However if you get under the coach you can't miss them.
The Starship- 1990 Grandvilla Unihome U300 40ft
6V92 Detroit Diesel w/ 4 spd Allison w/ retarder. Build# 3575 , Foretravel# 17895
The Shuttlecraft- 2015 Ford Explorer
Steve ( N6EKV ) & Lori ( N6JTD ) Faries  w/ Marlee our precious pup.
Patterson CA.

Re: 1991 40’ GV unihome Air tank drain

Reply #5 –
The forum comes thru again.
In the search box upper right corner of this screen , type in " Airtank valves R&R "  Make sure you select entire forum to search.

A thread from Chuck and Jeannie from 5 years ago should come up. Has pictures.

What a treasure chest of knowledge we are so lucky to have here! 
The Starship- 1990 Grandvilla Unihome U300 40ft
6V92 Detroit Diesel w/ 4 spd Allison w/ retarder. Build# 3575 , Foretravel# 17895
The Shuttlecraft- 2015 Ford Explorer
Steve ( N6EKV ) & Lori ( N6JTD ) Faries  w/ Marlee our precious pup.
Patterson CA.

Re: 1991 40’ GV unihome Air tank drain

Reply #6 –
Air Tank Valves R&R

Quote from: StevesRV –
  No wonder the on board compressor was cycling on too often— the tank air capacity was near nothing! 

One other observation is if the HWH compressor is filling the "Wet Tank" you may want to check and see which check valves are leaking through.

Mike
Pamela & Mike 97 U 320

"It's not what happens to you, but how you react to it that matters."

Re: 1991 40’ GV unihome Air tank drain

Reply #7 –
Just so everyone understands, a 91 U280/U300 (which I'm pretty sure is what the OP has) will not have the HWH system so no six pack or 12 volt compressor.  It has the manual air leveling and has a 120VAC 3/4HP air compressor under the stairwell.  Originally equipped, there is no dryer on that compressor.  At least on my coach the air compressor fills the entire air system (as witnessed when by seeing the dash gauges rise while it runs).  I typically see just a tiny amount of water on the rear tank drain and almost never see any on the front tanks - that said I live in a dry climate too so little is expected.  I can recall a couple of 91 owners who have had to replace the rear tank due to it rusting out from the inside - not expensive but maybe something to check.

If the OP isn't already planning on it I would replace all air bags if that first one was replaced due to age.  I had to replace all of mine for the first time about 10 years ago. 

I agree the engine air compressor dryer likely needs some attention.  It's located in the rear passenger side corner; accessed from under the coach.  If OEM, there is likely to be a thick layer of oily soot all around that area that will need to be removed (starting with a putty knife and finishing with a pressure washer if you have access to one) to see all the hose connections and the one electrical wire connection.  When I serviced mine I disconnected it (for the hose connections you needs some large adjustable wrenches) and removed the unit from under the coach.  Then I serviced it (new desiccant and seals)  on a bench and re-installed it.

The OEM dryer unit is a Bendix AD-4.  This was a common piece of equipment for semi trucks (of 30 years ago) and I would think a truck service center could perform this task.  You might purchase the service kit ahead of time since the AD-4 is so old kits maybe hard to find.  Some people just buy a new updated dryer but mounting to the coach and hose connections will need to be worked out.

John Fitzgerald
1991 U300 (SAI) Side Aisle Island Bed 40'
Detroit 6V92 with Allison Retarder
Meridian (Boise), Idaho

Re: 1991 40’ GV unihome Air tank drain

Reply #8 –
Or replace the entire air dryer with a unit with a spin on element. I was not hard to do with only a couple of fittings needed and allows for changing elements in a couple of minutes vs a much much longer R&R plus getting dirty.

Ours was not German but made next door in Poland. Works well. Brand New Air Dryer Assembly R955205 - Replaces Saver For 1200 Series... Check others toward the bottom of the page.

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: 1991 40’ GV unihome Air tank drain

Reply #9 –
On my 92 U300 I replaced my AD4 with a AD9 I got at peterbilt, nothing to change works perfectly.
Andy & Eileen
MONTROSE COLORADO
1992 U300  40' 6V92 TA
2016 4 Runner
1998 Jeep Grand cherokee

1998 Jeep Grand Cherokee) Build # 4135 Skp# 122921
 

Re: 1991 40’ GV unihome Air tank drain

Reply #10 –
My '93 U280 came with the AD-9 from the factory, so the '93-'94 period must have been when they changed over to the AD-9.  The factory rebuilt AD-9 is still readily available from NAPA and other sources.
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"