Most manufacturers of commercial vehicles recommend draining the moisture and oil from an air brake system on a ________ basis.
- quarterly
- daily ✓
- weekly
- monthly
Answer: B. daily
Most commercial vehicle manufacturers recommend draining the moisture and oil from the air-tank drain valves daily.
Why this is the answer
The air brake handbook says moisture and oil have to be drained from the tanks regularly, and that many manufacturers recommend draining the air-tanks daily through the drain valve at the bottom of each tank. It also reminds you to make sure each tank is fully drained and to watch for anything unusual in what comes out. Draining the supply tank first keeps collected moisture from flowing into the next tank. So the recommended interval in the handbook is daily, not some longer period.
Why the other answers are wrong
- A. quarterly — Quarterly is far too infrequent; the handbook ties air-tank draining to a daily manufacturer recommendation, not a few times a year.
- C. weekly — Weekly is longer than the daily draining the manufacturers are described as recommending.
- D. monthly — Monthly leaves moisture and oil sitting in the tanks far longer than the recommended daily drain.
Remember it
Think of the air-tank drain valve as part of your daily walk-around: bottom of each tank, supply tank first, and look at what comes out.