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Topic: Can anyone tell me what this is!? (Read 957 times) previous topic - next topic

Can anyone tell me what this is!?

Hi everyone, looking for some help. I have a 87 GV on oshkosh chassis and this thing just started leaking air when I release the park brake. When they are set it seals up. It's located right under the drivers side windshield. Been trying to figure it out for a while now. Any help is greatly appreciated.

Re: Can anyone tell me what this is!?

Reply #1 –
It looks like the vacuum system for the dash heat controls. My canister looks like the rusty can in your pic up top, it started leaking too with the ignition on, so I cut power to it for now to get me home.

I don't think mine was tied into the parking brake though, so it may be for something else. Sorry I'm no help lol. 

J.R.
99 U320 40' WTFE
Build # 5388

Re: Can anyone tell me what this is!?

Reply #2 –
yes a vacuum generator, the can is a vacuum accumulater tank for the dash heat controls.  Mine only functions when parking brake Is released.
Old Phart Phred, EIEIO
89 GV ored 36' #3405 300 hp cat 3208 ATAAC side radiator, mountain tamer exhaust brake

Re: Can anyone tell me what this is!?

Reply #3 –
Thanks.. any idea why mine could be leaking air all of a sudden? It's coming out of that black barbed fitting, is there supposed to be a hose that connects there and runs somewhere?

Re: Can anyone tell me what this is!?

Reply #4 –
 I also removed mine due to leaks.  It looks like it has a diaphram that may be failed.  Plug it off for now and look for an electric vacuum generator if the system works.
  Default for me is defrost  and the heat control cable  is faulty so I move the control  directly on the core box.  It's on the list !!  The list is getting shorter  tho.

Re: Can anyone tell me what this is!?

Reply #5 –
Thanks everyone! I'll just cap it off for now

Re: Can anyone tell me what this is!?

Reply #6 –
And, depending on cost/availability  of replacing with original, there are lots of 12 VDC vacuum pumps-- standard on most diesel PU's.
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: Can anyone tell me what this is!?

Reply #7 –
Quote from: Mlassalle –
Thanks.. any idea why mine could be leaking air all of a sudden? It's coming out of that black barbed fitting, is there supposed to be a hose that connects there and runs somewhere?
I've never seen that system before but reason tells me that if the vacuum pump is pump air after you release the parking brake, the valve that controls the parking brake is where you need to be look.

I don't have a separate parking brake.  I have wheel chocks.
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: Can anyone tell me what this is!?

Reply #8 –
Quote from: Old Toolmaker –
I don't have a separate parking brake.

?

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: Can anyone tell me what this is!?

Reply #9 –
Quote from: Old Toolmaker  -  4 minutes ago

    I don't have a separate parking brake.

Quote from: wolfe10 –
?



While a driveshaft parking brake would be nice to have, our GV relies on the rear drum brakes, the emergency braking spring inside the wheel cylinders.  The spring that stops you after you run out of air.

FWIW I packed a 3/4" wrench for Lynn trip home from Texas with the GV. Just in case there was a loss of air issue on one of the wheels.  The GV has wedge brakes.  No slack adjusters.
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: Can anyone tell me what this is!?

Reply #10 –
Quote from: Old Toolmaker –
Quote from: Old Toolmaker  -  4 minutes ago

    I don't have a separate parking brake.

While a driveshaft parking brake would be nice to have, our GV relies on the rear drum brakes, the emergency braking spring inside the wheel cylinders.  The spring that stops you after you run out of air.

FWIW I packed a 3/4" wrench for Lynn trip home from Texas with the GV. Just in case there was a loss of air issue on one of the wheels.  The GV has wedge brakes.  No slack adjusters.

Correct. Parking/emergency brake is on rear drum brakes-- spring applied, air released.
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: Can anyone tell me what this is!?

Reply #11 –
the vacuum generator is just a venturi i believe, no moving parts or diaphram.  put you finger on the exhaust port (the one that has nothing connected to it) and it will immediately blow off the vacuum hoses. and yes they blow air all of the time when parking brake is off.
Old Phart Phred, EIEIO
89 GV ored 36' #3405 300 hp cat 3208 ATAAC side radiator, mountain tamer exhaust brake

Re: Can anyone tell me what this is!?

Reply #12 –
Ok so it's normal for it to be blowing air when brakes are released? Maybe there was a hose that ran down under the coach that fell off. Because I can hear it very easily now.

Re: Can anyone tell me what this is!?

Reply #13 –
Quote from: Old phart phred –
...yes they blow air all of the time when parking brake is off.
I'm still not clear on the connection between the parking brake and the vacuum generator.

Does operating the parking brake (releasing it) open a valve that sends air pressure to the vacuum generator?
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: Can anyone tell me what this is!?

Reply #14 –
Quote from: Mlassalle –
Thanks.. any idea why mine could be leaking air all of a sudden? It's coming out of that black barbed fitting, is there supposed to be a hose that connects there and runs somewhere?
obsolete vacuum generator
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: Can anyone tell me what this is!?

Reply #15 –
If I remember right that was a Ford part. If it is leaking a lot of air then you probably have a vacuum leak. Block the line from the venturi to see if it has vacuum.
previous 1984 35 ft ORED 250 HP 3208 Cat       
previous 1998 40 ft U295 CAI 325 hp Cummins
previous 2003 40 Ft u320 build #6140 450 Cummins M11.                                                         
1999 Mazda Miata
Ron, Nancy, Tipper the cat, Max The dog
1997 U 270 36 ft build number 5174 8.3 Cummins

Re: Can anyone tell me what this is!?

Reply #16 –
Quote from: wolfe10 –
Correct. Parking/emergency brake is on rear drum brakes-- spring applied, air released.
When I sent Lynn off to Texas, I expected him to find "S" cam brakes.  I'm glad I didn't try to explain slack adjusters to him in the limited time we had to prepare.
As it was, his first return text, after the first 300 miles was "This thing flies!"
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: Can anyone tell me what this is!?

Reply #17 –
My black barb fitting is leaking too and I bought small plugs to cap it off but pressure would just blow it off again
Bob and Carol Cox
1987 gv 36 ft dp
Cat 3208t
2013 tundra crew cab lift

Re: Can anyone tell me what this is!?

Reply #18 –
Quote from: bigfoot –
My black barb fitting is leaking too and I bought small plugs to cap it off but pressure would just blow it off again
According to Reply #11, that black barbed fitting is supposed to exhaust air.  if you plug that fitting, you are defeating the design of the venturi vacuum generator.  Either leave it open and "bare", or connect a open-ended hose to it and let hose hang down behind the grill.
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"