Brake pedal valve

[snailexpress]

Some words about weak brakes as I was dealing with this recently.
Weak tractor brakes and good trailer brakes could have many roots.
1. Greasy brakes on the tractor. I.m not kidding. Quick lube bay monkey never watching grease coming out from S-cam bracket inside the brake. Then grease got heated and dropped on the drum. Brake shoe is done.
2. If truck equipped with advanced ABC the ABS module sensing truck load from rear air suspension air pressure sensor. So ABS is determine is truck loaded or bobtail. If sensor reading wrong or intermittent ABS thinks you are bobtail and weakened brakes. On my truck it was like locking trailer brakes up to trailer ABS release and truck was rolling without brakes till ABS is reset. Replaced the air suspension sensor and brakes are back to normal.