Buying a used diesel in the Upstate? What to check before you pay

A used diesel can be a great buy or someone else's problem with a fresh wash. The difference usually shows up in a few places, and most of them can be checked before any money changes hands.

Start with the paperwork

• Run the VIN at nhtsa.gov/recalls. Open recalls are free to fix at the dealer, and the list tells you what the truck is known for.
• Ask for service records. Regular fuel filters, oil and coolant tell you more than a clean interior does.
• Ask what's been changed. Modified trucks aren't automatically bad, but you want to know what you're buying.

Checks on any diesel

• Pull the dipstick. An oil level above full can mean fuel in the oil.
• Look at the coolant. It should be clean, full and the right type.
• Start it cold if you can. Watch for long cranking and white smoke.
• On the drive, feel for flaring or slipping shifts once the truck is warm.

Engine by engine

A few things are worth asking about by name:

• 12-valve Cummins: has the dowel pin (KDP) been fixed?
• 24-valve Cummins: how's the lift pump, and has the VP44 been replaced?
• 6.0 Power Stroke: what do oil and coolant temperatures read? A gap of 15 degrees or more points at the oil cooler.
• 6.4 Power Stroke: any radiator leaks or fuel in the oil?
• LB7 Duramax: any injector history?
• LLY Duramax: any overheating when towing?
• 2011-and-newer 6.7 Power Stroke, 2011–2016 LML Duramax and 2019–2020 6.7 Cummins: these use the CP4 pump. Ask whether it's been converted.

Get it looked over before you buy

A seller who's confident in the truck won't mind a second set of eyes on it. Call before you buy and we'll set up a pre-⁠purchase inspection. It's $199, and it tells you what the truck needs before any money changes hands.