Image
Terex Roadbuilding was the first transit-mix truck manufacturer to incorporate the new 2007 EPA emission engine technology into its full line of mixers. Many are now operating in the field. The first Terex Tier III mixer has more than 15,000 miles on it, with zero engine downtime logged.
Failing seals

In this hot engine operating environment, some have noticed serious problems with the alternator, serpentine belt tensioner, air conditioner clutch, and power steering pump bearings. Whether seals are failing and allowing grease to seep out, or the greases themselves are not standing up to the heat, has not yet been determined.

Charge air coolers (CAC) seem to be leaking excessively. Engine makers test CACs by pressurizing them to 30 psi and measuring time to leak down 5 psi. Some fleets report not being able to pressurize CACs beyond 7 psi. One fleet manager said he would not pressurize a defective part to two atmospheres of pressure, fearing a catastrophic failure that could injure a technician. He said it may be an OSHA violation.

“We wouldn't tolerate a radiator leaking 5 psi every few minutes. Why should we accept it with charge air coolers?” the manager asked. OEMs do so because turbochargers put out enough air to compensate.

Heat from under the hood and from under-cab DPFs have increased cab floor temperatures. A few managers claim you can cook food on some. But vertical DPFs on a ready-mix truck may radiate enough heat during regeneration to affect the mix in the barrel.

Many trucks have three-position DPF regeneration switches for automatic, manual-on, and prevent-regeneration modes. If a driver turns off regeneration to prevent operating in dangerous areas and forgets to switch back to automatic operation, DPF back-pressure can cause the engine controller to derate the engine. The driver will complain of low power, but it isn't the engine. Training corrects this.

Fleet managers also reported a growing number of truck fires. We think of diesel as a safer fuel because it has a much higher flash point than gasoline. But the high under-hood heat can raise the return line fuel temperature significantly. As a result, the diesel fuel in the tank is heated closer to its flash point. Ruptured lines and broken tanks are now more likely to result in fires than before.

Engine engineers are working on fixes. New designs using new materials will correct these problems, most likely before truck operators start pre-buying before the introduction of 2010 models, when engines will have to meet even more stringent regulations.

Until then, caveat emptor, or let the buyer beware.

— Paul Abelson if a former director of the Technology and Maintenance Council of the American Trucking Association. E-mailtruckwriter@anet.com.


Economists See Slow Truck Recovery

Commercial truck sales will experience a slow recovery after the first quarter of 2008, while heavy-duty sales are likely to grow faster in 2008 than medium-duty trucks, says Stephen Latin-Kasper, National Truck Equipment Association (NTEA) market data and research director.

Latin-Kasper was one of five economists who spoke at the 2008 Business and Market Planning Summit in October in Rosemont, Ill. Latin-Kasper also forecasts moderate interest rates and inflation, low unemployment, increased trade, and increased state and local revenues.

The economists also stated that:

  • Oil prices are near all-time highs, but when adjusted for inflation, they are below early 1980s prices.
  • The U.S. economy's industrial sector is regaining momentum after a slow start for the year; a two-tier recovery is on track.
  • Demand for ethanol will be a key factor in the increased demand for farm equipment.

The NTEA hosted the event with the National Trailer Dealers Association (NTDA). For a recap, visit www.ntea.com, or www.ntda.org.

Related Article