Paperwork first
- Service records and receipts.
- Open recalls by VIN at NHTSA.
- Engine dataplate matches the expected engine.
- Ask whether emissions parts are original and working. Tampered trucks can fail inspection and be costly to put right.
On the truck
- Cold start: see it start from cold, not pre-warmed. Watch for heavy smoke.
- Leaks, coolant condition and oil condition.
- Warning lights and stored codes, read with a scanner.
- Front end: track bar and steering play, uneven tire wear, signs of death wobble repairs.
- Hitch wear: gooseneck or fifth-wheel rails, bent receivers, worn rear springs.
- Test drive loaded if you can.
Get a pre-purchase inspection
A diesel shop can do checks you cannot, like blow-by, fuel system tests and full scans.
Diesel pusher motorhomes
- Engine and generator records. Check generator hours.
- Coaches that sat a long time need fluids, belts, hoses and tires checked by age, not just miles.
- Rear radiator condition.
- Have the chassis and engine inspected separately from the house systems.
Where this comes from
- Know Your Truck: Used truck inspection checklist
- Westco: Used diesel pre-purchase inspection
- NHTSA: Look up recalls by VIN
- U.S. EPA: Tampered diesel pickup trucks, review of enforcement evidence (PDF)
- Cummins: Motorhome quick reference guide, B6.7 / ISB (PDF)
- Tiffin Owner Hub: Cummins Onan generator FAQs
- Family RVing: Rear radiator cleaning
Last reviewed 2026-10-19. General information only: your owner's manual and service information come first.