conventional cabs and the people who run them
Started by linda_runs_i94 on Sep 15, 2025 in Engines, drivetrain and DOT
our 389 froze a brake line at a customer in Fargo last january. minus 28 in the morning and the trailer brakes stayed dragging until a mobile tech showed up with a torch and a lot of opinions. trying not to do that again.
truck has the Bendix AD-IS dryer. last cartridge change was sometime in 2023 going by the book in the sleeper. my co-driver swears by pouring air brake antifreeze into the glad hands every cold morning. the shop says that eats the seals. which one of them is right?
the shop, mostly. alcohol dries out the O-rings and valve seals over a few seasons, and on a truck with a working dryer you shouldn't need it. water in the lines in january nearly always comes back to a worn out desiccant cartridge, or a burned out heater on the purge valve that lets it freeze open.
change the cartridge every fall. check the purge heater with a meter at the connector on the bottom of the dryer. drain the tanks and see what comes out. if it's still wet after a new cartridge, the dryer isn't doing its job.
one more. a compressor that's pumping oil will ruin a new cartridge in a month. if the old one comes out oily, look at the compressor before you blame the dryer.
from the beet hauling years. we kept one can of alcohol in the side box for the one morning a year it saved us, and never poured it in as a routine. what fixed our freezing was heated automatic drain valves on the wet tank. old habits from the 70s trucks die hard though.
adding fuel since it's the same season. winter blend from the big stops in Iowa has been fine for me down to around minus 10. below that i run a treatment and change the fuel filter and water separator before the first real cold. keep the tanks over half full too so there's less air in there to sweat.
new cartridge in, purge heater checked out on the meter, tanks drained dry. co-driver still has his can in the side box, but he's promised it only comes out if something's actually frozen. bendix has the service data sheets for the AD-IS on bendix.com if you want to do the cartridge yourself. it's a strap wrench and fifteen minutes.
first real test this morning, minus 19 at the yard in Moorhead. air built in 3 minutes, no frozen lines. the thing that got me was the trailer ABS light, a corroded pin in the 7 way plug and not the air at all. dielectric grease on the plug every fall. i forget every single year.