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.
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.
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.
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.
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.