Way under the hood

Industry veterans Bob Deal and Lee Wittman recommend these other areas for used truck evaluation:

SURFACE CLUES. A shabby exterior, a trashed interior, doors that won’t shut right, windows that rattle – such signs often indicate an owner who also didn’t care about critical maintenance tasks.

TIRES. Scrubbing, feathering or other irregular tread wear points to alignment problems.

COOLANT. Whether it is conventional or extended life, it should be its proper color, not muddy. Discoloration could indicate a cooling system problem.

COMPARISON DRIVES. If you’re looking to choose from a matched set of fleet trucks, drive more than one to be sure to exclude one that sounds off-kilter.

Many of you looking to buy a truck in the near future will be shopping the used market. Either that’s what you normally do, or you’re trying to avoid – for good reasons or not – the 2007 engines.

There are more ways to evaluate a used truck than there are tires to kick on a tractor-trailer. All have value. Yet some of the more technical tests, which can precisely reveal certain problems, are relatively little used, according to a survey of Overdrive readers.

A dynamometer test, which determines engine strength by measuring drive wheel power, is probably the best of the technical checks, says Bob Deal, a former maintenance director for Signal Delivery who also has worked as a maintenance consultant with fleets and manufacturers. “While it’s running, you can have a guy look for leaks because it’s at maximum temperature,” he says.

“It is great if you can get it done, but practically it’s a very difficult procedure,” says Lee Wittman, who for 40 years has sold trucks, managed dealerships and developed truck remarketing programs. Most truck dealers don’t have a dynamometer, he says, so you’d need to get the truck to the appropriate engine dealer. The cost is between $100 and $200, Wittman says, but you get plenty of valuable readouts.

A blow-by test likewise produces great information but poses the logistical challenge of getting to a shop with the right equipment, most likely an engine dealer, Wittman says. The test puts pressure on each cylinder to measure air loss, thereby determining the condition of the piston, rings and liners, valves and head gasket. It normally costs $100 to $175.

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Analyzing engine oil by measuring worn material in the oil can provide a picture of the engine’s condition. It’s the technical procedure most frequently used by owner-operators, though it isn’t much use unless you have access to a series of readings over time to spot trends, Wittman and Deal say. Much less used by owner-operators is a similar analysis of the lube in the rear drive axles to examine differential wear.

If you’re considering a truck near a facility that can perform them, technical tests could be well worth your time and expense – sort of a one-time insurance premium. When that’s not feasible, investigate the technical side as much as you can through records of oil analysis and other maintenance, as well as inspection by a trusted technician.