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Topic: Bendix Air Cruise Leaking (Read 847 times) previous topic - next topic

Bendix Air Cruise Leaking

We brought our U280 home from storage for some remodel work and when the cruise was turned on we ended up with an air leak from the the valve (I believe its a valve) in the photo. It would drop the from 110 psi to 90 and then fluctuate for the rest of the 40 minute trip. My question is can these valves be rebuilt and what kind of problems might i run into if I disassemble this thing? We leave for South Texas in 3 weeks so I need it to be right.

Ian Minaert
1993 U280 Build #4324
Cummins 8.3, 6-Speed, Exhaust Brake, Aquahot
Valley Center, KS

Re: Bendix Air Cruise Leaking

Reply #1 –
Try uploading your picture again.  Thanks.

jk
Jack and Cathy
1992 U280 Unihome 36' Build #4034
Cummins 8.3 /  Allison MT647/ PacBrake
Apopka, FL / Barre Center, NY

Re: Bendix Air Cruise Leaking

Reply #2 –
Below is a "edited" diagram of the Bendix cruise control with lines added by Foretravel to tie in the air throttle system.

Which item on the diagram is leaking?  Some of those parts are available off the shelf - some are "unobtainable".

Hopefully you have a "easy" to fix leak.

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: Bendix Air Cruise Leaking

Reply #3 –
Thanks Chuck! For whatever reason my photo wont upload. I did break out the manual and found that it's the RV-1 pressure reducing valve and looking at your diagram, should be set to 60 psi. They look to be available online.
Ian Minaert
1993 U280 Build #4324
Cummins 8.3, 6-Speed, Exhaust Brake, Aquahot
Valley Center, KS

Re: Bendix Air Cruise Leaking

Reply #4 –
Whenever I need parts for our air system, I first go looking on eBay.  I've had good luck finding NOS (New Old Stock) Bendix valves there at very reasonable prices.  They always work fine, even if they have been sitting on a shelf gathering dust for years.

The RV-1 is adjustable, so if it isn't the correct pressure setting out of the box you can always fix that.
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: Bendix Air Cruise Leaking

Reply #5 –
Quote from: Chuck & Jeannie –
Below is a "edited" diagram of the Bendix cruise control with lines added by Foretravel to tie in the air throttle system.

Which item on the diagram is leaking?  Some of those parts are available off the shelf - some are "unobtainable".

Hopefully you have a "easy" to fix leak.


I *think* Festo has in the Festo Tiger Classic line an air valve that will do the job, and I'm sure they have a single acting cylinder that connected to a new bowden cable will open and close the "throttle."

At least that's my backup plan.
1992 Foretravel Grand Villa
U225 SBID Build No. 4134
1986 Rockwood Driftwood
1968 S.I.A.T.A. Spring
1962 Studebaker Lark
1986 Honda VF700C
1983 Honda VF750C
Charlie, the Dog was broken out of jail 24 Oct 2023
N1RPN
AA1OH (H)e who must be obeyed.

Re: Bendix Air Cruise Leaking

Reply #6 –
OK, so I replaced the RV-1 pressure reducing valve and stopped that leak. The coach is doing the same thing as before while driving though. I notice that pressure holds fine until the parking brake is turned off. The pressure will drop 10 to 20 PSI almost immediately. I've have previously replaced the main line from the compressor to the dryer due to a leak on a trip last year. We built up pressure to 110 psi, then having my wife shut down the engine and turning off the parking brake while I lay under the coach to listed for leaks and found nothing leaking (it was chalked and on level ground). Then we did the same thing and listened for leaks at the rear parking brakes and heard nothing. I'm at a loss so any suggestions are appreciated.
Ian Minaert
1993 U280 Build #4324
Cummins 8.3, 6-Speed, Exhaust Brake, Aquahot
Valley Center, KS

Re: Bendix Air Cruise Leaking

Reply #7 –
Does it continue to drop or does it stop at 10 to 20 psi. when you release the parking brake?
1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean

Re: Bendix Air Cruise Leaking

Reply #8 –
It drops 10 to 20 psi when the parking brake is turned off.
Ian Minaert
1993 U280 Build #4324
Cummins 8.3, 6-Speed, Exhaust Brake, Aquahot
Valley Center, KS

Re: Bendix Air Cruise Leaking

Reply #9 –
That might be what it takes to fill the brake release chambers if it starts building back up from there.
1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean

Re: Bendix Air Cruise Leaking

Reply #10 –
Do you see the pressure drop in both tanks, or just the rear brake tank?
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: Bendix Air Cruise Leaking

Reply #11 –
And, after the pressure (?one tank or both?) dropped, what was the "recovery time" back up to cut out PSI assuming at 1,100 or so engine RPM?
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: Bendix Air Cruise Leaking

Reply #12 –
Both tanks. sometimes it took a while to recover and others it recovered quickly.
Ian Minaert
1993 U280 Build #4324
Cummins 8.3, 6-Speed, Exhaust Brake, Aquahot
Valley Center, KS

Re: Bendix Air Cruise Leaking

Reply #13 –
I do not think you have a problem any more.  The pressure is going to drop once you release the parking brake because the parking brake canisters are taking on air to push against the springs that are trying to apply the parking brakes. 
2014 ih45  (4th Foretravel owned)
 1997 36' U295 Sold in 2020, owned for 19 years
  U240 36' Sold to insurance company after melting in garage fire
    33' Foretravel on Dodge Chassis  Sold very long time ago

Re: Bendix Air Cruise Leaking

Reply #14 –
But, the drop should ONLY be until the next "compressor on" cycle.  Once cut-out PSI is reached, it should not continue to be low.
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