Is it time to replace your old truck or tractor? Is it old enough that its engine has none of the exhaust-emissions equipment that’s been giving people fits in recent years? Have you decided to take the plunge anyway because your vehicle is just plain worn out?

Certainly you know the basics of truck hunting, like:

• Deal only with reputable people, whether dealers, fleets or individuals.

• Buy a truck that’s equipped for your kind of hauling. Usually that means it’s pulled the same kind of trailer as you do and carries the same kind of cargo.

• Choose the best one you can afford in miles and condition.

• If you don’t now use fuel-saving equipment, consider it. This includes aerodynamic fairings and low rolling-resistance tires, an automated mechanical transmission, and an aero-type model instead of one with traditional styling. These features can save you money, and the truck will still be nice to drive. Tip: An aero truck has far less stuff hanging on it, so is also much easier to wash.

• Drive the tractor or truck with a load so you’ll get a good feel for its power, ease of gear changing, noise and vibration, and handling.

• Examine tires for evidence of irregular wear, which could mean alignment work or repairs.

• Ask that the engine be given a blow-by test, which will tell a lot about the shape of its cylinders, pistons and rings, valves and other internal parts.

• Ask about warranties to cover major components, particularly the engine and its exhaust-emissions gear. You might have to buy coverage, but it could well pay off, especially if the engine’s never been rebuilt.

Those are the old but still valid rules for inspecting and evaluating a used truck. As we’ve hinted, however, you also need to be aware of exhaust emissions systems.

These are on most diesel-powered trucks built in the last 10 years. There are three types of equipment, based on emissions limits established by the federal Environmental Protection Agency (and California’s Air Resources Board). And while each cleanses diesel exhaust in different ways, all were troublesome when the new engines first came out, and many still are:

2002/04, when exhaust-gas recirculation (EGR) was applied. Exhaust gas mixed into the intake air goes into the cylinders, where it displaces oxygen to cool combustion; this reduces formation of nitrogen oxides, or NOx. The main trouble spots are EGR valves, which to the gas-air mixing and, because they’re in a hot, smoking environment, have failed early and often; and water-to-gas coolers, which can leak coolant into the engine’s air-intake piping and then into its cylinders.

2007, when diesel particulate filters were added the exhaust stream. The filter has an intricate honeycomb substrate made of ceramics that catches soot particles. The substrate can crack and break with vibrations, and can clog with soot and oil from cylinder blow-by or a failed turbocharger. Smoke might not appear at the stack until the filter’s loaded up; if there is smoke, the DPF is plugged or plugging, and the engine will be chocked off and shut down sooner or later. Tip: If you run in California, or will go there on regular runs, you need a truck with a DPF. CARB says so.

Caterpillar took a different route with “Acert” diesels, which piped cleansed exhaust gas into the engine, but they have not been entirely successful. EGR is still used on all ’07-spec engines. Tip: A new DPF costs $3,500 to $5,000, but reconditioned ones cost half or less. Ask for a recon.
 
2010, when most engine makers began dealing with remaining NOx by using selective catalytic reduction, or SCR. This squirts ammonia-bearing urea fluid at the exhaust inside a special dosing chamber. Ammonia neutralizes the NOx, but the fluid can crystalize in the chamber and in plumbing farther down the exhaust stream, and the injection gear can malfunction.
 
Navistar International avoided SCR by using higher amounts of EGR and various combustion changes to try to handle the NOx. The early engines had many problems, but later ones worked better, according to fleet reports. However, Navistar couldn’t quite reach the proper levels of NOx, and has committed to SCR.

All 2010-spec engines continue to use DPFs and EGR, though urea injection allows lesser amounts of it.
 

So, there’s a lot to be wary of.   You can protect yourself by demanding that all exhaust-emissions equipment is functioning properly and has been serviced recently. This is especially true of EGR valves and coolers, SCR dosing chambers, and diesel particulate filters. DPFs need periodic cleaning to remove soot not burned out under normal running and “regeneration” events, and ash from motor oil. Get proof that the DPF was cleaned recently.
 
Tip: A leaking EGR cooler can cause DPF failure, because coolant makes its way from the cylinders into the exhaust stream, through the turbo and into the exhaust filter. Put another way, if the DPF is found to be failing, it might be traceable to a leaking EGR cooler.
 
And ask about a warranty on the DPF, which National Truck Protection, a specialty insurance company, recently began offering. You’ll have to buy an accompanying engine warranty and together they might cost several thousand dollars, unless you can talk the seller into paying for them. However, the warranties might more than pay for themselves if something fails during the covered period – usually one year.
 
Be mentally prepared to face some of these problems with any modern truck, and budget for repairs. Maintain all systems regularly to avoid breakdowns.

Or you can avoid many of these troubles by buying a glider kit, which is a new truck with a used, rebuilt or remanufactured engine, transmission and axles. Engines are ’99-’02 models, built before EGR and everything else. Heavy Duty Trucking will have a complete report on them in its April issue, as well as a more detailed report on used truck trends.