Subaru Steering Systems Subaru Steering Systems

Two manual steering racks are used in Subaru vehicles: a constant gear ratio (CGR) rack … the appropriate model year Subaru Service Manual and follow the pro …

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Subaru Steering Systems Subaru Steering Systems Tilt Steering Column Rack And Pinion Steering Mechanism Subaru steering systems utilize a rack and pinion steering mechanism. As the pinion gear rotates, the rack moves left or right. Rack and pinion steering gives the driver precise controlover the wheels. The simple, compact design is easy to service. CGR  VGR Ratios Two manual steering racks are used in Subaru vehicles: a constant gear ratio (CGR) rack and a variable gear ratio (VGR) rack. The teeth on the CGR rack are equally spaced so theturning effort is equal throughout the turning range. The teeth on the VGR rack are spacedcloser together on the ends of the rack than in the middle. The turning effort decreases as theturning angle increases so sharp-radius turns are easier to make. Legacy and SVX Steering Racks Several different power steering racks have been installed in Subaru vehicles. The racks used in the L-series, XT, Legacy and SVX vehicles are similar. All have a one-piece gearboxand lack the external air vent distribution tube found on the rack in pre- 85 and carryovervehicles. However, the XT rack differs from the L-series rack in several ways. The XT rack ismade of aluminum and has a different control valve. Different types of hydraulic seals areused in the two racks, and each has its own unique special service tool. The power steeringrack in the pre- 85 model year vehicles and the Brat has a two-piece gearbox and an air ventdistribution tube. It also has seals, service procedures and special service tools that differfrom the other racks. Rigid Steering Column Three types of steering columns are used in Subaru vehicles: a rigid steering column, a tilt steering column and the XT and SVX tilt and telescoping steering column. The rigid steeringcolumn is found on L-series DL models, the Legacy standard model, and Justy vehicles. Therigid steering shaft does not tilt or pop-up, but is collapsible (a safety feature). The shaft isconnected to the gearbox by universal joints. Tilt Steering Column The tilt steering column is found on late-model L-series GL, Loyale, Legacy, and SVX vehicles. The tilt steering column features both tilt and pop-up operations. It is divided intotwo sections, upper and lower, connected by a universal joint. The L-series uses a frictiontype lock. By pushing down on the tilt lever, tension on a bolt is released, and the steeringcolumn may be tilted to an infinite number of positions. (Pre- 85 model year tilt steeringcolumns could be tilted to only eight positions.) When the tilt lever is returned, the bolt tightens to lock the steering column in position. The Legacy and SVX use a gear type lock.The  Lift Up lever tilts the steering column all the way up. The  Tilt Pull lever tilts thesteering column to the optimum driving position. End W rench Th e 4 Rack and Pinion SteeringMechanism CGR VGR Ratios Legacy and SVX SteeringRacks Subaru Steering Systems Subaru Steering Systems A pop-up/memory feature was added to the  85 and later model year L-series tilt steer- ing column. On  85 and  86 model year vehicles, depressing a button on the left side ofthe steering column releases the tilt shaft. The tilt shaft on  87 model year vehicles isreleased by pulling forward a knob located on the left side of the column. Spring actionlifts the column to its highest position. When the column is pulled down, a lock pin slipsinto a hole in the memory bracket, securing the column in its previous position. The Legacy and SVX memory function is controlled by disengaging a movable gear from a stationary gear. This causes the coil springs to tilt the steering column up. A mem-ory gear is engaged with the movable gear. A plate united with the memory gear is inter-posed between the movable and stationary gears. When the steering wheel is pusheddown, the movable gear is disengaged from the plate which allows the stationary gear andthe memory gear to return to the original position. XT Steering Column The XT steering column has tilt and pop-up features as well as a telescopic feature. A telescopic lever on the end of the steering column, when rotated counterclockwise, movesa lock key away from the steering shaft. This allows the control wing and the steeringwheel to be moved in or out in an axial direction. The maximum telescoping stroke is 40mm (1.57 in). The operation of the tilt feature and pop-up feature on the XT steering column is similar to that of the L-series tilt steering column. Moving the tilt lever down releases the steering column. The rubber bushing in the toe board deflects to allow the column topivot around the universal joint between the column and the gearbox. The dash also tiltsup and down with the steering column. XT Pop-up Mechanism The XT pop-up feature is operated by pulling a knob located on the instrument panel lower left side of the instrument panel. A cable connects the knob to the lockpin. Pullingthe knob retracts the lockpin from the column bracket, allowing the spring to force thecolumn upward. When the column is pulled down, it locks in its original position. Power Steering Rack System Subaru s power steering system contains a pump, hydraulic line, and a gearbox (rack). The hydraulic pump is a vane-type pump driven by the engine. It provides pressurizedfluid for the system. Oil Pump Operation The pump has two internal valves: a flow control valve and a relief valve. The flow control valve regulates the volume of power steering fluid delivered to the rack. Duringhigh engine rpm, the pressure in the pump overcomes the flow control valve spring. Thecontrol valve slides back to close off an oil passage to the rack and to open an oil returnport to the pump inlet. This reduces the power assist to the rack during high speeds,improving the steering wheel feel and response. Relief Valve Operation Pressure in the system is also controlled by the relief valve built into the flow control valve. The relief valve consists of a ball valve and a relief spring. When hydraulic pres-sure in the system reaches a specified value, the ball valve opens so that part of the working fluid flows into the return port via the fixed orifice. Power Steering Rack The gearbox consists of a control valve and a power cylinder. A power piston attached to the rack divides the cylinder into two chambers. As fluid is directed by the controlvalve to either side of the piston, the rack is pushed in the same direction in which thesteering wheel is being turned. Control Valve Operation Hydraulic fluid supplied to the rack is controlled by the rotary control valve. As part of the pinion gear shaft, the control valve directs fluid flow to one side or the other of thepower piston. When steering effort is not applied to the pinion shaft, hydraulic pressurein the valve and to both pressure chambers is held equal. Oil is directed from the centerof the valve back to the pump. As steering effort is applied, a torsion bar in the valve deflects in proportion to the resistance encountered. Fluid is allowed to pass directly from the pump discharge side to Power Steering System Oil Pump Operation Flow Control Valve Operation Relief Valve Operation Power Steering Rack 5 the pressure chamber, creating a pressure differential between the two chambers. Thishydraulic imbalance causes the piston and rack to move to one side. Piston movement causesfluid in the low pressure chamber to return to the pump through the control valve. The morethe torsion bar deflects, the greater the pressure differential becomes. The increased pressureassists in the turning effort. Steering System Troubleshooting Steering performance symptoms may be the result of a number of problems. The cause of the problem could be inside or outside of the steering system. For example, heavy or hardsteering could be a result of a malfunctioning pump, of low idle speed, of a defective controlvalve or of tires not properly inflated. When diagnosing the cause of a steering problem, care-fully follow the troubleshooting charts given in the appropriate model year service manual. Oil Leak Points Leaks in the gearbox should be confirmed before removing the gearbox from the vehicle. If leakage is suspected, clean the suspected portion, and turn the steering wheel from lock to lock approximately 30 or 40 times with the engine running slowly to verify the leakage.Refer to the service manual for the correct repair procedures. Power Steering System Pressure Testing If the troubleshooting procedures lead you to suspect a fault in the power steering system, perform a pressure test. The vehicle must be equipped with the specified tires and rims andthe tires must be properly inflated. Then, bring the engine up to operating temperature beforeperforming the test. Keep the following precautions in mind as well: Do not leave the pressure gauge valve closed for more than five seconds; doing so may damage the pump.  Do not hold the steering wheel in the full lock position for longer than five seconds; this may damage the pump.  Keep the engine speed at idle. Handle power steering fluid carefully; catch spilled fluid with shop cloths to prevent damage to the vehicle s finish. Power Steering Pressure Test Attach pressure gauge 925711000, adapter A 926210000, and adapter B 926220000 to the discharge part of the pump, then perform the three pressure tests listed below. Step 1: Regular pressure Engine idling, valve open: If No: 142 psi (10 kg/cm2) or less  Crimped Fluid line  Replace, Leaking fluid line  Tighten or replace, Clogged fluid line  Drain or replace. Step 2: Relief pressure Engine idling, valve closed: If No: L-series/Loyale SPFI: 40-55 kg/cm2 (569-782 psi)  Faulty relief valve XT/XT6: 60-75 kg/cm 2 (853-1067 psi)  Oil pump leak Legacy: 75-80 kg/cm 2 (1067-1138 psi)  Worn pump SVX: 78-85 kg/cm 2 (1109-1209 psi) In all cases replace pump. Step 3: Working Pressure Engine idling, valve open, If No: steering wheel turned stop to stop:  Faulty control valve  Replace. L-series/Loyale SPFI: 40-55 kg/cm 2 (569-782 psi) Loyale MPFI/XT/XT6: 60-75 kg/cm 2 (853-1067 psi) If Yes: Legacy: 75-80 kg/cm 2 (1067-1138 psi)  System Okay. SVX:78-85 kg/cm 2 (1109-1209 psi) Servicing The Steering System Note: Always refer to the appropriate model year Subaru Service Manual and follow the pro-cedure for removal of the SRS airbag module prior to any repair and servicing or removal ofthe steering wheel and steering column from all airbag-equipped Subaru vehicles. Th e 6 End W rench Subaru Steering Systems Control Valve Operation(No Steering Effort) Control Valve Operation(Steering Effort Applied) Steering SystemTroubleshooting Oil Leak Points Power Steering SystemCheck Column Removal Precautions  Reference service manual Section 4-3 for rigid column and tilt column servicing procedures. Always disconnect the U-bolt joint before loosening the column mounting bolts. Disconnect the wiring harness connectors before removing column. Install a 8 mm x 16 mm lock bolt to secure XT column. Remove the XT column carefully to avoid damaging meter and instrument panel. For proper steering wheel alignment, center the front wheels and scribe an alignment mark between the steering wheel hub and the shaft, prior to disassembly. When removing the steering column, always observe the precautions listed above. Gearbox Servicing Precautions Do Not: Crimp the pipes.  Scratch the rack or cylinder.  Clog the air passages. Do: Lubricate the seals/bushings. Install the seal lips toward the pressure area. Use the correct special tools. Follow the above precautions when servicing the steering gearbox. For detailed instructions on steering rack overhaul, refer to the appropriate model year service manual. Airbag Steering Column Installation Precautions:  Reference all airbag-equipped vehicles. Review the roll connector phasing procedures listed in the appropriate model year service manual, Section 4-3. 

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