Skip to main content ↑ ↓
Topic: check valve location? (Read 745 times) previous topic - next topic

check valve location?

My 1991 U300 has an air leak that allows the front tank to leak down to nothing in a few hours. The rear tank usually holds air pressure all night long. It doesn't matter if I have my front suspension pumped up or set all the way down on the ground, so it's not the airbags or anything associated with the suspension that's leaking. I can't hear any leaks when I'm rolling around on the creeper under the tanks. I bought a stethoscope and listened for internal leaks but didn't hear any. I'll check for external leaks with a bottle of soap suds next. I'm pretty sure it's gonna be the check valve on the front tank. Unfortunately I don't know where that check valve is. I presume it's inside one of the big fittings on the tank? I believe the tank on the driver's side is the front tank isn't it? Can I buy the check valve at a truck stop or do I need to go to NAPA or where can I buy it?
Scott Cook
1991 U300 36' 6V92TA
Old Town Penobscot 16
1984 Honda VF1100C (V65 Magna)

Re: check valve location?

Reply #1 –
Can't help you on the check valve but I had to replace the manual drain valve on each of the two front tanks.  We have the same year and model coach so it's something you might check with the soap bubbles first.  They leaked around the knob shaft.  Playing with them I could get them to stop but they would soon leak again.
John Fitzgerald
1991 U300 (SAI) Side Aisle Island Bed 40'
Detroit 6V92 with Allison Retarder
Meridian (Boise), Idaho

Re: check valve location?

Reply #2 –
Quote from: RRadio –
Unfortunately I don't know where that check valve is.

Scott, the check valve is on the supply end of each tank. It only control's back feed to the "wet tank"
Check drawing B-2031 in your supplied documentation, line #7
1993 U300, 6v92
build 4366
USAF retired, Flight Engineer, C124, C130
 ATP, A & E.  & ex AI

Re: check valve location?

Reply #3 –
One of the drain valves on the front tanks was leaking so I replaced both of them with plugs. I've been checking them for two years and I never get any water out of either of them so I don't see the point in having them as a potential leak. The only time I ever get water out of the rear tank is when I've been running the 120 volt AC powered compressor in a wet climate. I always check the rear tank as part of my preflight inspection so it's very unlikely any water will ever reach the front tanks.

I'm pretty sure it'll be the check valve on the driver's side front tank that's leaking. I also hear a small leak in my parking brake button sometimes but I wiggle it and it stops leaking. I read on here that the parking brake button can be disassembled and cleaned and it will stop leaking. Maybe I'll do that later when it starts to leak worse. Right now I want to find and fix the worst leak which is probably the check valve.

Does anyone know for sure if the driver's side tank is the front and the passenger side is the rear? Can I buy the check valve at a truck stop or do I need to get one at a parts store?
Scott Cook
1991 U300 36' 6V92TA
Old Town Penobscot 16
1984 Honda VF1100C (V65 Magna)

Re: check valve location?

Reply #4 –
Quote from: RRadio –
Does anyone know for sure if the driver's side tank is the front and the passenger side is the rear? Can I buy the check valve at a truck stop or do I need to get one at a parts store?
I released some air from the front drivers side tank.  The red needle on the dash pressure gauge dropped - I don't know if the red is front or rear.  I don't know about where to find a replacement check valve.
John Fitzgerald
1991 U300 (SAI) Side Aisle Island Bed 40'
Detroit 6V92 with Allison Retarder
Meridian (Boise), Idaho

Re: check valve location?

Reply #5 –
The white needle on my gauge went nuts when one of my rear airbags was leaking last summer. It went back to normal after I replaced the leaking airbag. I think the rear airbags are on the rear tank and the front airbags are on the front tank, but the drawing is a little confusing. If all these things are true that would mean the driver's side tank is the front tank and the red needle is the front air pressure... If somebody knows for sure it would be helpful information that I haven't read on this forum previously.
Scott Cook
1991 U300 36' 6V92TA
Old Town Penobscot 16
1984 Honda VF1100C (V65 Magna)

Re: check valve location?

Reply #6 –
Scott, you could call James Triana and get the scoop that way.
2025 Wanderbox Outpost 32 on F600 Expedition Motorhome
2015 Born Free Royal Splendor on Ford 550 nonslide version  for sale
Former Coaches  covering. 360,000 miles
1999 34 U270
2000 36 U320
2001 42' double slide U320
2018 Jeep Rubicon

Re: check valve location?

Reply #7 –
Yeah, that's what I'll do.
Scott Cook
1991 U300 36' 6V92TA
Old Town Penobscot 16
1984 Honda VF1100C (V65 Magna)
 

Re: check valve location?

Reply #8 –
Quote from: Bill Chaplin –
Scott, the check valve is on the supply end of each tank. It only control's back feed to the "wet tank"
Check drawing B-2031 in your supplied documentation, line #7
I replaced my check valve on the end of the tank with Bendix 800372 and the check valve in the center of tank with Bendix 800375
The selected media item is not currently available.Barry BEAM #16014
2003 U320 40' AGDS
Beamalarm, Foretravel technical help and specifications
"Whatever the mind can conceive and believe, it can achieve"