Big Rig Basics: Steering Right

It's a good idea to check your power-steering fluid level during your pre- and post-trip inspections, and replace as needed.It's a good idea to check your power-steering fluid level during your pre- and post-trip inspections, and replace as needed.

Basic Maintenance

Bill Litosky, the service manager at Bergey’s Mack and Volvo of Franconia, Pa., provided detailed information about how to maintain and troubleshoot the power-steering system.

1. Grease all the mechanical parts of the front suspension and steering system at least every 15,000 miles to keep parts like kingpins from binding. This may require putting the front axle on secure jack stands to take the weight off the wheels — check your owner’s manual. Hard steering is commonly a result of neglect there, not trouble with the power steering.

2. In your pre- or post-trip inspection, check the fluid level. Refill with the fluid recommended on the reservoir, normally Dexron II or Dexron III transmission fluid. Wipe the dipstick cover off, pull the dipstick out and put in fluid until it reaches the upper line. On most reservoirs, there is a filler cap that is larger than the dipstick cover that you remove to pour in the fluid. On some, the filler cap and dipstick are combined.

3. Also inspect all places along the high-pressure supply hoses and low-pressure return hoses, and at their connections, for leaks or corrosion. (High-pressure hoses have SAE screw-on type connectors or quick connectors, while low-pressure hoses have hose clamps.) Make sure the hoses are not rubbing anywhere and that protective coverings are intact. Most Class 8 trucks now have steering pumps driven by the geartrain on the engine. But some medium-duty trucks still use belt-driven pumps. If necessary, check the belt to make sure it is tensioned properly and is not frayed or glazed smooth by slippage. Have hoses, corroded connections, or belts replaced as necessary.

5. Change the filter about once a year, or as recommended.

6. On some reservoirs, you may need to remove the top by rotating it counter-clockwise with a wrench, and then pulling it off. Use a syringe to remove a few ounces of fluid and pour it into a clean glass jar. Inspect if for significant amounts of bright metal or obvious moisture content. If it is contaminated, have the system flushed and the fluid replaced. Replace the filter with a new one. Refasten the filter by tightening the wingnut, or reinstalling the reservoir top with a wrench, using new gaskets.

7. You may be able to replace the pump yourself if you’re experienced with a wrench, but some pumps are hard to get to. For example, the pump on a late model Volvo with a D13 engine is driven by the engine’s rear geartrain and accessible from underneath. The small blue hose with a screw connector is the high-pressure one, while the large hose with the clamp is the low-pressure return line. Use new gaskets and bleed the system thoroughly before driving.

If a hose needs replacement, the standard SAE screw-on fittings will be much easier than the newer quick disconnects. Screw fittings are tapered, and if you just turn them tight, they won’t leak. Quick disconnect designs require a special tool to disconnect, and at $50-$75 a pop, it may be cheaper to just have the hose replaced.

Once the hose is replaced, refill the reservoir and start the engine, rotating the steering wheel back and forth and keeping the reservoir full to prime the system. Make sure the system is full and the steering response steady before operating on the road.

Litosky says hard steering in both directions suggests a worn pump, while hard steering in only one direction suggests a bad steering box. But hard steering not attributable to the mechanical parts of the system must be troubleshot by a technician using an expensive set of gauges. Get a pro to troubleshoot the system to be sure.

If the problem turns out to be a steering box, it will have to be replaced with an exchange remanufactured one. Litosky says this is a difficult job that takes two technicians, and is especially difficult when the box is mounted on the inside of the frame, as is often the case. This is a job best done by the pros. But taking care of the fluid and filter and greasing the steering to minimize the stress on the power-steering system will delay all major repairs.

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