Truck engines are hellish environments, so overlooking belts and hoses is an invitation to disaster. Since good maintenance is no guarantee against premature failure, knowledgeable technicians know to change out belts or hoses if even a hint of trouble is spotted. Away from the shop, your best preventive maintenance is to target belts and hoses during pre-trip inspections to spot potential problems.
Compared to the chemistry set required to test a truck’s coolant mix, checking the hoses and fittings in the cooling system is a relative snap. The primary diagnostic tools are with a driver all the time: his hands.
“Coolant hoses degrade from the inside out,” says Frank Burrow, manager of warranty and customer support at Red Dot, a supplier of A/C systems and components for heavy-duty vehicles and off-highway equipment. “At a glance, there’s rarely an obvious sign of wear and tear. Palpating a coolant hose is one of the simplest ways to gauge its condition.”
Hose deterioration is caused by an electrochemical reaction between the coolant and metals in the system, such as steel clamps, a copper heater core or a cast-iron head. Tiny cracks develop in the tubing, typically near the hose ends, allowing coolant to reach and cause wear to the reinforcement yam.
As the hose degrades, it sheds debris into the coolant. “You have foreign material circulating through the heater core,” Burrow says. Any places the hoses or fittings are fastened, clamped, connected, bent or otherwise secured are potential wear points. The same goes for places where hoses are not clamped or supported but should be.
Follow these tips to get long life from coolant hoses:
INSTALL HOSES PROPERLY. Consider the hose’s natural curl as it’s unspooled from the reel. Coolant hose should be installed so the bend is in the most relaxed position, not pulling away from the fitting. “That load, however slight, is an opportunity for pressure to build and a weak spot to form,” Burrow says.
USE CLAMPS THAT PROVIDE UNIFORM PRESSURE. There can be as many as 50 hose-clamp applications on a heavy-duty vehicle, as well as a variety of different clamping systems. For the cooling system hoses, consider the hose type, size and material in choosing clamps that provide uniform tension and sealing, especially in low temperatures.
CONSIDER USING TORQUE-SPECIFIC CLAMPS. Some clamping systems have specific torque ratings and require special tools for installation and removal. While screw-type clamps are simple and easy to find, more complex torque-specific clamps aren’t as susceptible to overtightening and do a better job at providing constant equal pressure on the hose.
DO A HANDS-ON INSPECTION. Turn the system off and squeeze the hose near the ends. If it feels spongy, it should be replaced. Manually examining the hose also can pick up scruffs, gouges, bulges and abrasions that are hard to see. Feel for moisture, seepage or excess dirt and grime around fittings, clamps and connections.
“Obviously, touch and feel aren’t going to replace the service equipment of a qualified technician,” Burrow says. “But if you’re an owner-operator or a mechanic doing a routine PM, they’re a good first step in the troubleshooting process.”
Serpentine belts have replaced multiple belts on most of today’s engine systems, so many trucks have only one or two belts. As with hoses, a driver’s hands are the simplest tools for making sure that engine belts are in good working condition.
Follow these tips to get long life from belts:
LOOK FOR SIGNS OF FRAYING. Because of the high speeds of moving engine belts, the outer edges are sensitive to small misalignments. Any lateral play introduced to a rotating belt quickly can wear its main body. When there is fraying, not only should the belt be replaced, but this type of wear also indicates an alignment problem that needs to be addressed.
LOOK FOR BRITTLENESS. Belts should be supple and flex easily. Older belts usually show their age with cracks in the top, sides and bottom. Any belt that cracks and resists flexing should be replaced immediately.
CHECK BELT TENSION. On modern engines, spring-loaded tensioners automatically keep belts at the proper tension. They also help eliminate overtightened belts that can strain bearings, leading to eventual misalignment or failure. Check tension by pressing down on the belt to gauge its “give.” While slight play is normal, movement of about ¼-inch up or down is usually a sign that the tensioner needs to be replaced.