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.
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.
yes a vacuum generator, the can is a vacuum accumulater tank for the dash heat controls. Mine only functions when parking brake Is released.
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 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.
Thanks everyone! I'll just cap it off for now
And, depending on cost/availability of replacing with original, there are lots of 12 VDC vacuum pumps-- standard on most diesel PU's.
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.
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.
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.
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.
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?
obsolete vacuum generator (http://www.foreforums.com/index.php?topic=27357.msg223782#msg223782)
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.
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!"
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.