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Professor Paul: Practical PM
Know the lingo

By Paul Abelson, senior technical editor

There’s an old adage that states, “An ounce of prevention is worth a pound of cure.”

That’s what preventive maintenance for trucks is all about. You do maintenance on a planned basis in order to prevent catastrophic failures on the road. The “ounce of prevention” consists of regular oil and filter changes, lubrication and thorough examination of wear items. The “pounds of cure” avoided are road service calls, missed deliveries and downtime.

Back in the day, oils needed to be changed every 8,000 to 12,000 miles, with “dry” (no oil changes, just chassis lubrication) maintenance done roughly halfway between “wet” intervals.

Since then, a number of advances have affected maintenance. Most have been in anticipation of, or as a result of, emissions regulations.

While oil refiners are continually upgrading their products for competitive reasons, trying to exceed established standards to get you to buy their products, it is the establishment of new standards that brings real progress to engine oils.

As new requirements for oils were recognized, the American Society for Testing and Materials and the American Petroleum Institute establish either higher performance standards for existing tests or established new tests for approving motor oils. Those changes are recognized as standards CH-4, CI-4, CJ-4 and so on. They are each tied to the then-newest industry-accepted strategies to meet emissions limits.

When the EPA implemented the 2004 emission standard to reduce nitrogen oxides (NOx) 15 months early in October 2002, the then-new oil standard, CI-4, was ready to control heavier soot loadings because of exhaust gas recirculation (EGR).

The next significant advancement was the use of diesel particulate filters (DPF) to control particulate matter in the exhaust, which is primarily of soot and metallic ash.

Shortly after introduction, CI-4 was found to be close to what was needed, but not quite there. A modified set of requirements was introduced, called CI-4 Plus.

To minimize ash formation and to suspend increasingly finer soot particles, CJ-4 oil was introduced in 2006, just in time to reduce DPF filter plugging. When 2010 engine regulations further reduced NOx, no new technologies were needed inside the engine.

New oil formulations weren’t needed for either of the engine technologies – selective catalytic reduction or advanced exhaust gas recirculation – used to meet the 2010 emission standard.

For 2010 engines, recommended oil drain intervals are unchanged from 2007 practices. It’s not just the advances in oils that make today’s longer drain intervals possible. New computer controls are a major factor.

Moore’s Law, named for Gordon Moore who founded Intel, states that the computing power of a micro chip doubles every 18 to 24 months. Using the conservative number, computer capability increased 16 times between the 2002 start of the current series of emissions controls until the launch of 2010 engines.

The faster, more capable computers allow precision timing of multiple fuel injection pulses. The result is not only improved mpg, but more complete combustion with less soot being created. Based on computer power, the EPA 2007s had about eight times more control over the combustion process.

You may remember the rash of breakdowns that occurred in 2003 and 2004, due mainly to excessive under-hood heat. Had EPA not altered the launch date for the 2004 emissions regulations, there would have been time to discover and correct these problems.

The motive was noble, to make up for alleged cheating on NOx output of EPA 1995 and 1998 engines. The 15-month advance brought the “law of unintended consequences” to life. It took time and several product modifications to control the excess heat from EGR.

Recirculating exhaust back into the air intake system dilutes the air to lower the rate at which fuel burns. That lowers NOx. It also introduces a great deal of heat under the hood. That added heat caused the problems and led to modifications to the preventive maintenance routine for post-10/02 engines.

EGR coolers and valves were among the first components to show heat-related problems. Soot, carbon deposits and combustion byproducts can build up inside the cooler. This affects the EGR valve as well as temperature, pressure and flow sensors.

EGR coolers don’t plug unless there are other, more serious problems. The procedures for addressing EGR cooler diagnosis and maintenance are spelled out in TMC Recommended Practice RP361.

Charge air coolers are essential for maintaining the density of intake air. Leaks often occur where hoses connect them and the intake system. Cracks can develop at fittings. A good ear and a stethoscope will help detect leaks. If none are heard, clean the charge air coolers and, for that matter, all heat exchangers with low pressure water as shown in TMC RP358.

Used oil analysis is useful in diagnosing liquid cooled charge air cooler problems. Aluminum, potassium and sodium are in brazing flux used in the manufacture of coolers. If aluminum measures less than 30 parts per million (ppm) with potassium and sodium both above 70 ppm, check for coolant leaks.

Most heat-related problems arise with the drive belt system and belt-driven accessories, Lubricants are permanently sealed, but excessive under-hood heat can destroy their effectiveness. Heat affects bushings and solid polymer bearings resulting in drag on rotating parts. In post-10/02 engines, check idlers, pulleys and alternators for free rotation. If you feel drag, get the component repaired or replaced.

Check drive belt condition at every preventive maintenance. There are two types, each with slightly different inspection procedures. V-belts rely on manual adjustment with a slotted mounting bracket. Glazing on the sides of the V is a sign of slippage because of tension loss. It could be because of normal wear or loosening of the mounting bolt. Frayed edges are a sign of misaligned pulleys.

Multi-ribbed V-belts can develop additional symptoms. Ribs can crack, leading to chunking, the loss of multiple sections of ribs across the belt face. When cracking or chunking are found, the belt has little life remaining and should be replaced.

Wear debris can also accumulate in the pulley grooves or in the ribs of the belt. This is defined as “pilling” by TMC. The accumulation is not normally a concern as driving usually cleans the belt. Excess accumulation, however, can lead to belt noise, vibration, and slippage and, in extreme conditions, belt “walk-off” when the belt actually leaves the pulley. In that case, clean the pulley grooves thoroughly and replace the belt.

Gravel penetration refers to any granular debris accumulating on the belt face. It is often self-correcting but if pinholes or bumps are seen on the back (smooth) side of the belt, replace it immediately.

Heat affects fan clutches. Check them for proper operations. If they are functioning, but operate at the wrong temperatures, check sensors. (See Maintenance Q&A)

Preventive maintenance has not fundamentally changed for years, but high underhood temperatures from EGR have made periodic checks more important. Be thorough and you’ll prevent problems on the road. LL

Aug/Sept Digital Edition