Larry N.
Well-known member
Ouch!
Air system pressure fluctuation
- Thread starter billbenham
- Start date
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billbenham
Member
- Joined
- Jan 4, 2016
- Posts
- 10
Both of the little air pressure warning switches on the brake treadle valve assembly are leaking where the lower screw terminal is. Having removed and disassembled them, it looks like there's no way they can be made not to leak so I'm looking for a better one that won't leak. Then I'll be looking for the next leak after that.
Laura & Charles
Well-known member
Thanks for the update, Bill!
Gary/Lou:
I paid much closer attention yesterday. Compressor kicks on at 83 psi and off at 123. Most times the front and rear drop steadily and together all the way to 83 and repressurize together to 123. But sometimes the front only gets down to 111-115 by the time the rear hits 83. Those times the front doesn’t start repressurizing until the rear has reached the same psi as the front. I had my bride time it while I was driving. It varied a bit depending on how smooth and straight the road was, but the rear bled down to between 4’ 15” and 4’ 45”. The rate of bleed for the rear did seem impacted by whether the front was bleeding or not.
I’m hoping the intermittent nature of the front is a clue. I didn’t stop any place level enough to get stationary timings. I’ll be trying again for those today.
Gary/Lou:
I paid much closer attention yesterday. Compressor kicks on at 83 psi and off at 123. Most times the front and rear drop steadily and together all the way to 83 and repressurize together to 123. But sometimes the front only gets down to 111-115 by the time the rear hits 83. Those times the front doesn’t start repressurizing until the rear has reached the same psi as the front. I had my bride time it while I was driving. It varied a bit depending on how smooth and straight the road was, but the rear bled down to between 4’ 15” and 4’ 45”. The rate of bleed for the rear did seem impacted by whether the front was bleeding or not.
I’m hoping the intermittent nature of the front is a clue. I didn’t stop any place level enough to get stationary timings. I’ll be trying again for those today.
Gary RV_Wizard
Site Team
The common places for constant leaks are the ride height valves, air dump valves, and the brake treadle valve. Lesser places are air accessories like an air horn or step cover. Could also be a cracked air bag, but that wouldn't be typical in a 2012 vintage coach.
The reason for a engine-off measure vs travel is that the suspension ride height valves are actively working during travel, and maybe the brake valves too (as needed, obviously). That would be "working as designed" rather than "leak", though a badly adjusted ride height valve might be working overtime.
A 5 minute leak down isn't really unsafe - the compressor is spec'ed to be able to cope with a massive leak and still provide enough air to brake the rig to a safe stop. Obviously, though, you want to fix it before it does become unsafe.
The reason for a engine-off measure vs travel is that the suspension ride height valves are actively working during travel, and maybe the brake valves too (as needed, obviously). That would be "working as designed" rather than "leak", though a badly adjusted ride height valve might be working overtime.
A 5 minute leak down isn't really unsafe - the compressor is spec'ed to be able to cope with a massive leak and still provide enough air to brake the rig to a safe stop. Obviously, though, you want to fix it before it does become unsafe.
billbenham
Member
- Joined
- Jan 4, 2016
- Posts
- 10
So I checked the system recovery while enroute on the interstate with engine turning 1800 and found the compressor comes on every 7 minutes for only about 10 seconds. Tells me the system demand is 10/420 or 2.4% of the compressor capacity. This ought to be a good data point to refer to in the future for this rig. If the percentage starts rising then look again for new leaks. This sure has been an interesting discussion.
