Just realized my old air dryer was stealing my brake pressure all along

Had a Freightliner in my shop last Tuesday, driver complaining about soft pedal after a few hard stops. I chased it for two days. Replaced the compressor governor, checked the slack adjusters, bled everything twice. Finally on the third morning I noticed the purge valve on the air dryer was weeping just a little when I shut the engine off. Rebuilt the dryer cartridge for 80 bucks and the air system holds like new. Turns out a worn dryer can let moisture push past the check valve and that little bit of air bleed adds up over time. The driver said he'd been feeling it for weeks but thought it was normal in the cold. Anyone else ever had an air dryer cause a brake pressure complaint that other guys blamed on the compressor?

2 comments

2 Comments

gray_schmidt827d ago

Hate that you had to fight it for two days, man. That's the worst kind of problem, the one that hides in plain sight and makes you second guess every other part on the truck. I've had a Wabco do almost the exact same thing, just a tiny hiss you only catch if you're kneeling next to it with the engine off. Eighty bucks and a Saturday morning beats the hell out of a brand new compressor install, so at least you caught it before that mistake.

christopher_flores4626d ago

Fair point @gray_schmidt8 and yeah, a hiss is a hiss. But for me, two days of chasing it means the cheap fix already cost me more in time than the compressor would have. I get where you're coming from, but sometimes you gotta cut your losses early and just swap the whole unit.