Vehicle Maintenance Schedule Checklist

Oil should be between the hash marks on the dipstick and amber to light brown — milky or gritty indicates coolant intrusion or overdue change. Top up coolant only at the surge tank when the engine is cold; opening a hot system is a burn hazard and masks a real leak.

FMCSR Part 393.75 sets minimum tread depth at 4/32" on steers and 2/32" on drives and trailers. Anything below is CVSA OOS. Check cold pressure against the door-jamb placard; underinflation by 20% is a roadside violation.

Build to governor cut-out (~120 psi), shut off the engine, fan the brake pedal. Low-air warning must activate by 60 psi; the red parking-brake and trailer-supply valves must pop out between 20 and 45 psi. Failure here is an immediate OOS condition.

Walk-around with headlights, markers, and four-ways on; have a helper or use the trailer light tester to confirm brakes and turn signals. A single inoperative required lamp is a Part 393.9 violation logged to the carrier's CSA Vehicle Maintenance BASIC.

Log honestly in the ELD or paper DVIR — copy-pasted "no defects" entries are the single most damaging document in post-accident discovery. Defects route to the shop queue before the unit moves.

Create the ticket in Fleetio, Whip Around, or RTA with the unit number, the defect category, and photos. OOS items block dispatch until the mechanic signs the DVIR repair certification under Part 396.11(c).

Low DEF triggers a 5-mph derate that strands the truck on a shoulder. Confirm no active regen faults on the dash and that the last parked regen completed; repeated incomplete regens point to a clogged DPF that needs shop service.

Streaking or torn blades are a Part 393.78 violation and a wet-weather safety issue. Replace blades in matched pairs; top off washer fluid with a winter-rated formula November through March.

Brush corrosion off posts, apply dielectric grease, and torque hold-downs. Resting voltage below 12.4V on any battery in the bank flags it for the next service; a bad cell drags the whole bank and kills starting in cold weather.

Visually confirm the jaws close fully around the kingpin with no gap between the trailer apron and the fifth wheel plate. A high-hitch or partial lock is the classic cause of trailer drop-offs at the first turn out of the yard.

Shoe lining below 1/4" at the thinnest point or pushrod stroke past the CVSA adjustment limit (typically 2" on a Type 30 chamber) is OOS. Check all wheels at applied pressure — a single out-of-adjustment brake counts toward the 20% rule.

Squeeze coolant hoses cold — spongy or rock-hard means imminent failure. Check gladhand rubbers and air lines for chafing where they cross the catwalk; a blown service line drops trailer brakes at highway speed.

Soot trails at clamps or DPF joints indicate a leak that lets exhaust into the cab. Loose stack brackets shear the V-band clamp and drop the muffler on the highway. Tighten or tag for shop repair.

The Part 396.17 annual inspection decal expires the last day of the punched month. Equipment driven past expiration is OOS at the next roadside. Schedule the re-inspection 60 days before expiration to avoid a service-truck rush.

Most heavy-duty diesels (Cummins X15, Detroit DD15, PACCAR MX-13) run a 35,000-50,000 mile drain interval on CK-4 oil. Pull an oil sample to Polaris or Blackstone every other change to catch fuel dilution or wear-metal trends.

Move drives forward and check for irregular wear that indicates an alignment problem. Torque lug nuts to manufacturer spec (typically 450-500 ft-lb on hub-piloted wheels) and re-torque after 50-100 miles — wheel-off events are catastrophic.

Replace primary and secondary fuel filters together; prime the system before cranking to avoid an air-lock no-start. A plugged air filter shows up as low boost and rising EGT before the dash ever lights up.

Use a Midtronics or carbon-pile tester on each battery individually, not the bank. Replace the full set when any battery fails — mixing a new battery into an aged bank kills the new one within a quarter.

Test nitrite and pH on the existing ELC before deciding to flush versus extend. Cavitation pitting in wet-sleeve liners from low SCA is the most expensive way to learn this lesson.

Check king pin play with a pry bar, drag link and tie rod ends for slop, U-joints for the dime-on-edge test. Sagging air bags or broken leaf springs over a U-bolt are common findings on units running heavy hauls.

Use a qualified inspector per Part 396.19 — typically an in-house tech who has completed a recognized program or any state-certified CVSA inspector. The completed Appendix G form lives in the maintenance file for 14 months minimum.

Tag the unit OOS in the TMS so dispatch cannot assign loads. Schedule the repair, complete it, then re-inspect against the same Appendix G items before clearing OOS status and applying the new decal.

Pull drums on all axles, replace shoes, S-cam bushings, and slack adjusters as wear dictates. Verify chamber stroke at 90-100 psi after reassembly — a fresh brake job that pushes past stroke limits is still OOS.

Check tank straps for rust-through, crossover lines for chafe, and the DPF for cracked substrate via differential-pressure data. A failed DPF runs $4,000-$8,000 and is often misdiagnosed as a regen problem until the truck won't start.

Upload the signed Appendix G, parts invoices, and any sample reports to the unit's file in Fleetio or RTA. Part 396.3(b) requires retaining maintenance records for the period the vehicle is under control plus 6 months — auditors will ask.