Buying a used vehicle is always stressful, especially when it is a used diesel truck that can still be pretty pricey. It is not uncommon to see a truck that is several years old, with 100,000 miles on it that is still over 20 grand. How do you know that you are not getting a lemon? Well, you can never really know when buying a truck how long it will last you, but here are some important things to check.
1. Miles on the truck. This one seems obvious, but sometimes gets overlooked with diesel trucks because of the fact that diesel engines last much longer than their gas counterparts. I include this though because while the long block of a diesel engine may last 500,000 miles, we have a lot more parts on a modern engine that can fail. Not to mention the other large components of the powertrain that can wear out. If the owner claims a part of the drivetrain has been replaced or rebuilt, ask to see receipts; always play it safe by assuming the work was not done if the owner cannot confirm it. Try to get an understanding of what the owner primarily used the truck for, there’s a big difference between 100,000 miles of hauling and 100,000 miles of daily commute. While yes, you don’t need to look at mileage as much on a diesel truck, it still should be something to pay attention to.
2. Fluid condition and level. It is important to look at the engine oil, transmission fluid, coolant, and brake fluid. Make sure that each fluid is at the proper level. Everything but the engine oil should look clean, and not smell burnt. If you have the truck for a long test drive, and feel confident in yourself, I would also check the fluid level and condition in the differentials and transfer case. It is important to check for leaks while looking at the fluids, better to get underneath the truck and get your jeans dirty now than pay for costly repairs down the road. While a $6 leaking differential cover gasket might look like a cheap and easy fix, there’s no way of truly knowing how low that fluid is and how much damage might be done while it’s still in the owner’s driveway.
3. How the engine runs. Get the engine up to operating temperature, does it miss at all? Get the truck up to highway speeds. You don’t have to squeal the tires but be sure to accelerate hard at different speeds. Does it miss under load? Is there blue or white smoke coming from the exhaust? How easily does it build boost? Look for any “hiccups” in how the engine runs. If a check engine light is present, swing by an auto parts stores on the test drive; most read codes free of charge, or bring your own scanner along.
4. How the truck handles. Take the truck around a parking lot maneuvering front, back, left, and right. Take the truck over a couple speed bumps. Is there any popping sounds, possibly indicating ball joint failure? Does the transmission shift into gear easy? Engage high and low settings if necessary and ensure each works. Does the steering wheel turn smoothly and return with minimal effort? When you have the truck at highway speeds, are there any groaning sounds from wheel bearings? When you stop the truck, does it pull to one side, indicating a seized up brake caliper?
I would say most used vehicles could generally use some TLC, somewhere in the ball park of $500-$1,000. Once again; most of the time, there is no way to tell when a catastrophic failure will occur, but you can use these things to get a good picture of the health of the vehicle overall.