Troubleshooting Power Steering Problems

[Home] Click to Return to Benz Spring Home Page
Although this document was written with Truck (class 7 and class 8 semi's) in mind, the lessons and application of the tests listed here can and will reduce the amount of time it takes to evaluate Power Steering Problems.

Because the Steering Gear is a very complex and and equally misunderstood component of the steering system, it commonly gets blamed for problems in drive ability when the fault may be elsewhere. To assist you in correct diagnosis of your steering system, here are some good steps to follow.

  1. Drive the Vehicle

    If possible, drive the vehicle and verify the type and extent of the steering problem. If you are unable to duplicate the steering complaint, ride with the driver and observe the nature of the problem. Notice the point at which the problem occurs and itís nature. Provide preventive maintenance services on the steering components, grease and re-torque and drive it again.

  2. Listen to the Driver

    In every case, the driver will be able to tell you more about the steering difficulty than you can know. Is the system warm or cold? Is the vehicle always empty or loaded when the problem occurs? Does it only occur with one driver? Does the problem disappear only at low RPM conditions? Does the problem only appear after slowing down from highway speeds and then go away? Does the problem only appear turning in one direction? Does the problem only appear in one spot in the turn of the steering wheel?

  3. Give the Vehicle a Visual Inspection

    Look for signs of vehicle abuse. Inspect the tires for previous impacts and side scuffs. It is easy to see an operator that takes pride in a piece of equipment and keeps it in good condition as well as equally easy to see a poorly maintained and abused piece of equipment.

  4. Check the fluid first

    Many factors contribute to looseness in the steering system. This looseness may be caused by something as simple as the fluid levels not being maintained at the recommended levels. Air entrapment may cause delayed action and/or over-reaction in the steering system. Oil foaming, fluid color and a burnt smell are all signs of problems related to the pump. As a pump degrades, chrome plating will flow through the system; this will usually be observed as a shine quality or reflective quality in the oil. Although water may be hard to spot, usually by draining a quart or better, water can be seen if present. Water, when heated, will react like air entrapment and degrade the overall system performance. Many vehicles can be found with old engine oil in their power steering systems. The suspended fuels, acids, carbon and sludge found in used engine oil quickly cause power steering hoses to break down.

  5. Look at the Tires

    Under-inflation of a vehicleís tires can cause high steering effort, road wander and poor recovery. Improperly mounted or unbalanced tires can cause shimmy and excessive fluid heat. The presence of tire cupping and abnormal wear are all signs of alignment problems and troubleshooting should begin after the front end alignment has been checked.

  6. Examine the Front End Components

    Excess wear can cause road wander, high steering effort as well as shimmy and over-steering. Tie rod ends, drag links, idler arms, pitman arms, king pins, ball joints, steering arms, ubolts, and steering columns, each with a little wear, all add up to a lot of potential wear and road wander. Correct preventative maintenance with inspection and lubrication will extend the life of steering components.

  7. Watch the front end Articulate

    Sometimes the best way to look for looseness in a steering system is to securely block the rear end from moving and to start the engine and cycle the steering from right to left. Have the driver provide feedback as he turns and look for over motion, looseness and binding. Try this first loaded, then unloaded, as well as with the front end completely off the ground. The same smooth movement should be present under all loads. Watch the steering column, looking for smoothness and a lack of jerky movements. Remember, the vehicle linkage and engine can pose a great amount of danger to life and limb, so exercise care.

  8. Truck? Inspect the Frame and Cab
    Car? Inspect the Steering gear to frame connection

    As the front end linkage turns, forces are applied to the frame laterally. The frame relies on the cross members to stabilize it through the turning movements with little to no frame flex allowed. A little known fact is that many Class 7 and 8 vehicle manufacturers rely on the front bumper as the vehicle's front cross member. After market bumpers as well as broken, removed and loose bumpers can contribute to road wander as well as shimmy. As the steering gear turns under load, see that the steering box is tightly bolted to the frame and no movements between the two are seen. Since, on many steering gear models, the gear requires a slip joint on the steering column for the valve to shift, loss of motion in the steering column can force the valve to react erratically. In more severe circumstances, cab mounts can crack and break, allowing the cab to sit down on the steering gear. This by itself can cause any number of steering difficulties.

  9. Inspect the Hydraulic System

    Look at the steering gear, hoses, valves, cylinders and the pump. The hoses should be reasonably flexible, the painted components will discolor and hoses become stiff, due to heat. Under operation, the pump, when power steering is applied, will draw down the engine RPM if properly operating. Control valves on linkage systems need to be free to operate smoothly without sudden motion as well as be reasonably clean. Dirt acts like an abrasive when allowed to enter a steering system and degrades smooth movement. For steering systems to operate correctly, they need proper pressure, measured in pounds per inch, and proper delivery, measured in gallons per hour. A pump may be able to pump to twelve hundred pounds pressure, but not be able deliver the flow to operate a steering gear. Conversely, a pump may be able to pump eight gallons per hour, but not exceed one hundred pounds. Steering pressure and flow requirements are determined by the size of the vehicle and intended weight capacity. Consult the vehicle manufacturer or steering gear manufacturer for minimum acceptable standards.

  10. Back to the Front End Components

    Perform ALL wear tests as recommended by the vehicle manufacturer. This should include the King Pins, Tie Rod Ends, Axle Spindles as well as all other front end components. Articulate the front end by hand with the pitman arm removed from the steering gear. The front end should articulate freely without binds and noticeable noises. Set the front wheel bearings with a torque wrench as recommended by the vehicle manufacturer. Check for excessive movement in the springs, hangers and other attaching parts.

  11. Inspect the Rear of the Vehicle

    A poorly attached body will allow the frame to flex and wear frame cross members. A loose rear suspension will cause the front end to appear loose (rear steer).

  12. Steering Gear

    The steering gear should now be considered as a potential problem. Lash adjustments can be checked against factory standards and if the gears exceeds those standards, repair or replacement is necessary. In order to insure a safe steering system, follow these guidelines.

Testing the Steering System

  1. Heat

    Perhaps the easiest test and possibly the most important is to test the temperature of the steering gear. Warning: High Temperatures may exist in the steering system so do not expose unprotected skin to the steering components or hydraulic oil.

    The typical Steering gear is rated to run at 100 degrees above the outside air temperature. This means that the outside case temperature may be allowed as high as 200 degrees on a hot day. Some steering systems rely on the steering gear housing to dissipate the residual heat in the system. Interruptions of air flow may compromise steering gear longevity. As the steering gear is exposed to excess heat, the seals in the gearbox begin to harden and over time, leakage or bypass flow may become a problem.

  2. Noise

    Although steering systems naturally emit noise, by carefully listening to the steering system and making comparisons to other vehicles, problems can be diagnosed here. A growling or gravelly noise are signs of air entrapment or pump failure. Popping noises in the steering gear are far from natural and require proper attention. Sharp noises or clunking sounds need immediate care.
  3. Oil

    Oil is the lifeblood of the steering system and requires careful consideration. The oil when originally installed was usually a caramel or reddish color. Any change from those colors may indicate steering system problems. As long as the system has received new oil throughout itís life, the oil should hold itís color with little change.

  4. Oil Supply

    The oil supply is perhaps the most overlooked and most important component of the steering system. It is the single item from which all parts rely, and without proper attention, it can easily be your biggest source of problems. The oil supply component of the steering system includes the reservoir, return line, oil cooler (if installed) and filter. Careful periodic maintenance of the steering system should include oil changing along manufacturers guidelines, filter replacement (usually installed in the base of the reservoir), suction side fittings and reservoir to pump connection consideration. All suction side fittings can contribute to air entrapment and oil foaming.

  5. Gear Articulation

    Warning: The Steering System Generates great amounts of power and may and can break limbs or crush your body. Never stand in a position where the steering linkage, tires, wheels or engine components may grab or trap your body.

  6. Engine Off Inspection

    As a co-worker slowly turns the steering wheel in a continuous stop to stop motion, observe the steering column for steady and non-jerky turning. The steering column should move freely and without noise with slip joints if installed exhibiting smooth movement.

    Note on end play: Some steering gears such as the Ross HF54ís, HF64ís, HPS70ís, HS70ís are built with as much as 1/2Ē of input shaft movement in and out of the steering box. On these models with the engine off, shaft movement in and out of the steering box is completely normal and does not warrant repair. This movement corresponds to internal valve action and is completely normal. However, under engine on conditions, this movement, although present, will be greatly reduced but system valve action can only be tested with a suitable pressure and flow gauge.

    End Play on other systems: Ross manual, HFB52, HFB64, HFB70, Shepard 292, 392, M90, M100, Saginaw and Bendix are built to have NO end play of the input shaft and should be repaired if movement here is observed.

    As the Steering Box is being rotated, notice the movement of the tires and wheels. Are the spindles turning evenly, smoothly and without jerks? Does the the linkage appear to move freely or does it appear to move in a jerky fashion? As the steering box reaches itsí stops, notice the change of motion as the steering box is turned in the opposite direction. Do the shaft connections appear tight? Any movement between the column and the input shaft as well as movement between the pitman arm and the output shaft will create road wander.

    Have your same co-worker steer the system in short and rapid movements, right to left. Any looseness between the steering column and the input shaft as well as the output shaft to pitman arm will become apparent in this maneuver.

    Any movement of the steering input shaft laterally should not be permitted.

    As the steering box begins to build up pressure, observe for the horizontal movement of the shafts in their bearings. Although the steering box may be designed with a tolerance in the shaft to bearing fit, excessive wear can allow seals to leak and gear teeth to bind inside the steering box. If both shaft connections appear tight and functional, during the rapid left to right turning motion, notice any lash or looseness in the mesh of the two gears inside of the steering box. The sum of all of the looseness in a steering system can add up to a substantial amount of free play.

  7. Frame

    For proper performance, the steering box relies on the vehicle frame to maintain its' location for both uniform range of motion as well as balanced steering feel. A well maintained steering system must exhibit no movement between the steering box, its' sub-frame mountings, and the vehicle frame. The frame by nature was designed for optimum performance in distributing the weight of the vehicle to the suspension elements. Its' tall cross section allows superior abilities to manage the vertical loads that exist in a vehicle. The steering system loads the frame horizontally though, with the upper and lower frame flange in addition to the cross members designed to counteract these forces. As the steering system articulates, observe any frame flex as well as cross member to frame movement.

  8. Engine on Testing

    For correct testing of engine on steering system performance, the only effective tool is a pressure/flow metering test set. This fixture, available form Benz Spring Co. of Washington, will more than pay for itself in the avoidance of unwarranted parts purchases and wasted mechanics hours. This test set includes two hoses, a pressure gauge, a metering valve, a flow gauge and is irreplaceable in correct steering diagnosis. The test set is plumbed into the steering system between the pump and the steering box and performs the following evaluations.

  9. The Pump

    Although the steering box appears to be the unit which is doing the job of Power Steering, an understanding of the pump is necessary for proper diagnosis. The pump is the item which develops the power that the steering box turns into rotational energy, that in turn, turns the vehicle. Without proper Pressure and Flow, the steering system will fail to perform properly. The steering box is at the mercy of the pump to provide constant pressure and flow for the steering box to maintain top performance, with many a complaint about road wander has been cured by a pump replacement. Each pump manufacturer designs each pump for a specified flow at a given pressure. For proper steering diagnosis, these specifications need to be taken into consideration.

  10. Testing the pump

    Prior to testing the pump, an evaluation of the hoses is necessary. The tests listed here can and will subject the existing hoses to pressures higher than normal and can result in catastrophic leaks or complete failure. Any marginal hose must be replaced prior to any pressure testing.

    The first step in testing the pump is to plumb the power steering test set in the high pressure hydraulic line, between the pump and the gear.

    Warning: Power steering fluid is flammable. Any leak which may allow oil to drip or spray on a hot engine component can and will catch fire.

    The First Test is to verify that the pump is providing flow to the steering box. With the test set valve open, observe the flow meter to see the low pressure gallons per minute reading. This comparison of this flow reading to the free flow specifications of the pump will give you an initial indication of the abilities of the pump. Failure here warrants pump replacement.

    The Second Test involves the static pressure reading on the pressure gauge. With steering system at rest, any pressure measured here will correspond to restriction in the steering hydraulic system. Although some pressure here is normal, comparison to factory standards will establish what your static flow should be and how the system you are testing is performing. Failure here warrants evaluation of hose performance, steering box restriction due to contaminants as well as reservoir problems.

    The Third Test involves momentarily shutting down the metering valve to measure the relief valve setting. Comparison of this reading to factory specs will allow you to judge the performance of your pressure delivery system.

    Warning: This test generates high heat and high pressures in the pump. This valve should be closed momentarily in order to not damage the pump due to heat, or not damage a hose which may cause a fire hazard or allow a leaking stream of hydraulic fluid to cut flesh.

  11. The Gearbox

    Upon inspection of the gearbox, any leaks need to be addressed prior to troubleshooting the system. Any leak in a hose at or between the fittings that cannot be halted by tightening a hose fitting requires hose replacement. It is never acceptable to allow a steering system to continue leaking. Power steering leaks reduce the fatigue life of leaf springs, compromise brake performance, cause the buildup of dirt and contaminants on the chassis and create ecological hazards that will not be tolerated.

    Steering gear leaks are signs of failed seals, worn shafts and parts damage. Any visible leaks warrant complete steering gear rebuilding. Seal replacement without consideration of shaft and component wear will prove dangerous.

    Test Four. Have your same co-worker begin turning the steering wheel left to right, one turn of the steering wheel from center in each direction.

    Warning: The Steering System Generates great amounts of power and may and can break limbs or crush your body. Never stand in a position where the steering linkage, tires, wheels or engine components may grab or trap your body.

    Observe the pressure and flow readings as the front end articulates. The pressure and flow requirements should be fairly uniform in either direction. The system when operating correctly should have a balanced feel in either direction with a balanced set of readings.

    1. Any condition where pressure is developed in one direction only points to potential valve problems within the steering gear.
    2. Any condition where pressure and flow drops below minimum manufacturer's specifications point to potential pump or fluid delivery problems.
    3. Any condition where pressure and flow readings change in an erratic manner indicate a myriad of potential problems. Problems here can result from:
      • Front end bind conditions (king pins, steering linkage, etc.).
      • Steering gear valve problems.
      • Air entrapment.
      • Oil Contamination
    The correct interpretation of these readings are necessary for proper diagnosis. Careful analysis of the comparison of these readings to factory specs will lead to a good diagnosis of the power steering components.

    Test Five: Before we can continue testing, we need to get a feeling for what type of pop-off valve or relief valve we have internally in the steering box. If small screw adjustments appear on each housing end, then it appears that a manually adjustable pop-off valve is present. The pop-off valves are designed to relieve gearbox hydraulic pressure before the steering gear allows the spindles to turn into the axle stops. These adjustments are critical to proper steering performance and their setting differs with different vehicle, axle and steering box manufacturers so correct adjustment can only be attained after study of the manufacturer's service publications. We can, though, test whether they are or are not functioning. By bringing the gearbox and hence the spindles to their stops, a pressure drop can be observed as the valves pop-off (hence their name). If the spindles fail to hit their stops before the gear bottoms out, then the axle stops are not adjusted incorrectly. The steering box cannot be used as the axle steering stops, this will cause non-repairable gearbox damage and potential catastrophic failure under operation. Steering boxes without pop-off valves may either have internal non- adjustable pop-offs or pressure relief valves. Those with internal pop-off valves may operate correctly during the axle stop pop-off test. However, those gears equipped with pressure relief valves will give erroneous readings. Test Five is useless with those gears.

    Test Six: Steering Gear Bypass Flow. In conditions where pump pressure and volume (flow) are sufficient, AND all components test within manufacturer's specifications AND all other tests indicate a completely normal steering system, AND high steering effort persists, then and only then should Test Six be attempted. Test six involves bringing the steering gear up to operating pressure by adding a block between the axle stops and the spindles. This test should only be attempted by experienced professionals and can be dangerous. By blocking the axle stops, the steering system can be brought to maximum pressure and at that time, the flow gauge will be read. This flow reading corresponds to the internal leakage within the steering box and should be done only momentarily. This test is also ineffective on gearboxes with internal pressure relief valves.

    The pressures and forces generated here are substantial and should only be considered after taking appropriate safety precautions. Stay away from the steering linkage, axle and wheels if you attempt this test.

    A Word On Adjustments

    Due to the critical nature of steering gear systems, no adjustments should be attempted without first consultation of the correct service manual for that steering system or service manual for the vehicle or chassis involved. If the correct manual is not available, do not proceed without assistance or without the proper settings for adjustment or repair.

In Conclusion
Many factors influence steering gear troubleshooting. Here is a list of common complaints and their usual cause.

The Final Word
The following represents some common sense guidelines for the maintenance of steering systems. Although most are well known, each deserves a repeat.

  1. Do not remove a steering gear cover and replace it with the gear installed in the vehicle. Dirt introduced into a steering system can cause serious problems.
  2. Never adjust a steering gear while either shaft is connected to the linkage. The readings you get will not be true.
  3. Always re-seal a steering gear in a clean environment.
  4. Always have a trained rebuilder perform internal adjustments.
  5. Always flow test a steering gear prior to installation verifying the operation of pressure relief, pop off valves, and steering control valve.
  6. Never rebuild a steering gear involved in a collision where the front axle was affected. Most shafts, unless completely broken, will not exhibit any outward signs of problems, even when present.
  7. Never install or remove a pitman arm with a hammer!
  8. Always use the fluid recommended by the manufacturer, or if unknown, consult a rebuilder for information.
  9. Always perform preventative maintenance functions on the steering system. Change fluids and filters within the manufacturer's guidelines. Systems without filters should have them, systems without coolers should consider them.
If you have any questions regarding this troubleshooting guide, or have unresolved steering systems questions, please call

If you have any comments, please address or click here to:
Benz Spring Co of Washington
700 S. Forest St.
Seattle WA 98134-2196
206-624-7733 206-623-4356 Fax
[Home] Click to Return to Benz Spring Home Page
Benz Spring Co maintains facilities for the remanufacture of nearly all steering systems from cars to class 8 trucks. Brands rebuilt include:

Power Steering Boxes
Power Steering Pumps

[Home] Click to Return to Benz Spring Home Page
This information is presented by Benz Spring Co for the sole use of our customers to assist in the diagnosis of power steering problems. This document is not intended to replace a good mechanic and represents a compilation of real life experiences in the troubleshooting of steering systems. However, the individual designs may validate or invalidate this information so consult an experienced mechanic for any additional difficulties. This page is copyrighted by Benz Spring Co 1995.