2014 Peterbilt 389 discharged all the air to fix air leak (firewall manifold) and now my tanks all build air, no leaks, but no secondary air pressure. The brakes work, the trailer air works, but the secondary needle won’t budge. No transmission air, seat air etc. I’ve even pulled both primary and secondary lines off the air dryer and both are pushing air.
All air tanks full no secondary pressure
Discussion in 'Trucks [ Eighteen Wheelers ]' started by dirthaller, May 2, 2025 at 4:00 PM.
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I think Pete used check valves at the tanks on those trucks. If you've got air outta the dryer ports, what happens when you pull the tank drain?
dirthaller Thanks this. -
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Is there a check valve coming out of a tank that just serves secondary?
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dirthaller Thanks this.
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Also, did you replace the air manifold?
dirthaller Thanks this. -
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I even tried teeing the two outputs of the dryer together. So primary and secondary were both charged in case it was a pressure problem off the dryer. Purge valve and governor works fine.
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