Hibernation for unused trucks

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“We were told by management to come up with procedures for storing a very large number of our unused trucks,” a manager at one large fleet told CCJ recently. “Trouble is, we haven’t been able to find much information on the subject.”

Understandably, this fleetman isn’t eager to disclose to the world his name and company, but his plight is hardly unique. Thousands of trucking operations face the same problem, albeit on a smaller scale, as this large-fleet manager faces.

The unfortunate combination of slowing freight volumes and an unprecedented surge in the supply of late-model used trucks has left many fleet owners with a dilemma. They face cash flow pressure to rid themselves of the notes and lease payments that accompany underutilized equipment. But they also find themselves upside down in those trucks, owing thousands or even tens of thousands more than the units are worth in today’s market. Essentially, many operators can’t afford to keep their trucks – and they can’t afford to get rid of them. And simply defaulting on notes and leases is unacceptable for a fleet operator wishing to stay out of legal and credit trouble.

In this environment, many carriers have just parked their surplus trucks and hoped for the best. But fleet owners are making a big mistake if they park trucks for months on end without any preparation. If you find yourself needing to store vehicles safely for up to six months, take the necessary steps – especially in the areas of electrical systems, tires and engine fluids – to protect your investment. Rather than letting your equipment deteriorate and set you up for some unwelcome repair bills later, take some simple and often no-cost steps to put your trucks in “sleep mode.”

Electrical systems
The weakest link in the storage equation – or at least, the one that will get you into trouble the fastest – is batteries. “If you leave even a fully charged battery connected in an inactive vehicle, it’ll be dead within a month to a month and a half,” says Bruce Purkey, president of Purkey’s Electrical Consulting in Rogers, Ark., and vice chairman of the Technology & Maintenance Council’s Electrical & Instruments Study Group. “Today’s vehicles all have electronics and, although they require only a tiny amount of current to maintain their memory, it’s enough to kill a battery in a month or so.”

There are two important reasons to avoid complete battery discharge, Purkey says. First, it causes “hard sulfation” – a process whereby the battery plates crystallize and the battery will no longer take a charge. “It’s an irreversible process,” Purkey says. “Also, once it starts, the plates are very susceptible to damage from normal movement and vibration.”

The second reason to avoid complete discharges is cold temperatures. When a battery is fully charged, its electrolyte freezes at -83 degrees F, Purkey notes. “Not much to worry about there. But when it’s discharged, it’ll freeze at 32 degrees F, breaking the inter-cell connections and cracking the case.”

So what’s the best way to prevent costly battery replacement when a truck is pressed back into service? You could use a float-type charger if the vehicle is near an electric source, says Purkey. “These keep batteries at the proper state of charge, without overcharging and boiling away the electrolyte like a common trickle-charger will. And there are all types of battery-preserving and monitoring devices on the market that work well. Some products from Intra and Pulse-Tech come to mind.”

But the easiest and cheapest way is to fully charge the battery (see temperature-correction chart at right) and disconnect the ground cable. “The battery will hold its charge for about a year,” Purkey says. “Don’t even take it out of the truck. It’s fine where it is.”

Removing the positive cable will accomplish the same thing, but it’s not advisable, Purkey points out. It’s safer to disconnect the ground cable because there’s no danger of creating a high-amperage short circuit if your wrench accidentally touches a grounded surface while you’re working.

Because weather protection agents compounded into tires are more effective when tires are exercised, tires on a stored vehicle should be protected from the elements. Otherwise, weathering, or ozone cracking, can become pronounced, as in this tire sidewall.

You spend enough on tires already; for most fleets, they are the No. 1 maintenance expense item. There’s no reason to incur additional tire expenses needlessly by letting prolonged storage ruin tires.

Not everyone agrees, however, on how best to preserve tires. Consider flat-spotting – a process that occurs when a tire’s steel belts gradually conform to the surface they’re resting on. The result is often low- and/or high-speed vibration once the vehicle is returned to service. Usually, it’s temporary.

“We’ve done some research at our San Angelo, Texas proving ground,” says Al Cohn, marketing manager for Goodyear Tire & Rubber in Akron, Ohio. “After three months of sitting and supporting a vehicle, tires are fine. It’s not until after five or six months that you start to see some flat-spotting. But it’s a gradual process; it’s not like one day they’re fine, and the next day they’re not.”

For that reason, Cohn recommends that if storage of six months or longer is anticipated, fleet owners should put a vehicle “on blocks” and drop inflation pressure to 15 psi.

If a vehicle must rest on its tires, Cohn suggests increasing inflation pressure to 25 percent above normal service pressure. The surface under a vehicle should be firm, level, well drained, and free of petroleum-based contaminants, which can attack rubber, he says. Avoid blacktop or oil-stabilized surfaces.

Other manufacturers take a different view. “We don’t insist that vehicles be blocked up,” says Doug Jones, customer engineering support manager for Michelin North America in Greenville, S.C. “Depending on how many trucks we’re talking about, that would be pretty impractical. What we do recommend is a thorough, pre-storage inspection. Don’t wait until you need the truck again to check tire condition.”

Michelin also recommends inflating stored tires to their maximum rated pressure. This higher pressure puts less stress on a tire’s cables, Jones says. “Plus, any tire is going to lose about 3 psi a month, so start high and check them every three months.”

Jones also advises against parking for protracted periods on freshly turned soil or dry concrete, as these can draw beneficial oils out of a tire’s rubber. He recommends washing tires – including the spaces between duals – with a brush, soap and water before storage to remove any petroleum-product residue picked up during use.

“We see no need for blocking up a stored vehicle,” insists Greg James, engineering manager of commercial products for Bridgestone/Firestone in Nashville, Tenn. “We’ve seen no permanent damage to belts caused by flat-spotting.”

James urges a pre-storage inspection as well. “Fix any penetration by foreign objects to prevent moisture from infiltrating into the belts,” he says.

Today’s tires are built with weather protection agents compounded into them, but these agents are more effective when tires are exercised. Because you can’t count on idled tires to protect themselves from the elements, you should take steps to shield them from weathering or ozone cracking. Goodyear’s Cohn recommends that tires be protected with an opaque waterproof covering.

“Keep stored trucks away from ozone sources,” adds Michelin’s Jones. Ozone sources include direct sunlight, transformers, electric motors, in-use welding equipment, mercury vapor lights and power lines. Even if a tire isn’t rolling, it’s still aging,” Jones says.

“Park trucks next to each other, so they shade each other,” says Bridgestone/Firestone’s James, who suggests covering tires on the end trucks. James also recommends against washing tires during storage. A tire’s anti-oxidation oils naturally leach to the surface to protect tires from ultraviolet and ozone, he says. “Washing them off removes this protection and depletes the tire’s oil reserve.”

Finally, advises Goodyear’s Cohn, stored vehicles resting on their tires should not be moved during extremely cold weather. Tire components can become brittle, and may not be able to move off their flat spots without damage.

Engine fluids
Whether you’re talking about a truck engine or reefer unit, managing engine fluids on idled equipment requires some judgment. In practice, it may be enough just to stabilize fuel and keep it clean and dry, depending on length of storage. “Buy a good fuel-treatment product with a stabilizer and biocide,” advises George Kaiser, a chapter president of the American Truck Historical Society in Collingdale, Pa. This step, Kaiser says, will help prevent fuel breakdown and the growth of microbes.

Microbes can grow in fuel tanks at the interface between diesel and any water in the tank. Left unchecked, they feed on diesel fuel and eventually grow into colonies that can plug filters and fuel injectors. Keeping moisture out of fuel tanks by keeping them full of fuel is also good insurance against microbes.

Your engine manufacturer may have more cautious guidelines for storage. But how “to-the-letter” you want to follow them depends on your own sense of cost vs. benefit and, perhaps, your appetite for risk. For example, if you’re storing a vehicle for one to six months, Cummins recommends, among other things, a procedure for running an anti-rust preservative oil (spec MIL-L-644, Type P-9) through the fuel system, including injectors.

“These procedures are admittedly conservative,” notes Bill Stahl, director of OEM service for the Columbus, Ind.-based Cummins, “because they have to allow for all climates and geographic areas where the engines might be stored.”

The company also recommends draining the oil pan and filters. The pan, says Cummins, can be left empty until the vehicle is ready to use, unless the storage period is to exceed six months. In that case, the pan should be filled with a preservative oil (MIL-L-21260, Type R-10, Grade 2, SAE 30W).

On the other hand, it may be OK to leave the oil alone, provided it’s a fairly fresh fill. “Today’s premium, over-the-road engine oils have strong enough corrosion-fighting additive packages to last through at least six months of inactivity, with no known problems,” says Jim McGeehan, manager of engine oil technology for ChevronTexaco in Richmond, Calif.

And there may be other considerations. For instance, what if the storage period falls into a fringe area, like three-and-a-half weeks or six-and-a-half months? Which recommendations do you follow? Check your engine service manuals and, as noted, use your best judgment as to what seems reasonable for your application.

While almost everyone hopes and waits for a better business climate, properly storing unused equipment – rather than letting it languish – can help your investment in rolling stock maintain the best value possible.

Fully charged? It depends
The easiest way to preserve a battery during an extended period of inactivity is to keep it fully charged with the ground cable disconnected. That sounds simple, but don’t overlook the effects of climate when you are testing for a full charge.

According to Interstate Batteries, Dallas, a fully charged battery should have a specific-gravity reading of 1.265 in each cell. Remember that hydrometers are calibrated to read specific gravity at an electrolyte temperature of 80