The power steering pump supplies all the power assist used in power steering systems of all designs. There are various designs of pumps used by the truck and van manufacturers but all pumps supply power to operate the steering systems with the least effort. All power steering pumps have a reservoir tank built onto the oil pump. These pumps are driven by belt turned by pulleys on the engine, normally on the front of the crankshaft.
During operation of the engine at idle speed, there is provision for the power steering pump to supply more fluid pressure. During driving speeds or when the van is moving straight ahead, less pressure is needed and the excess is relieved through a pressure relief and flow control valve. The pressure relief part of the valve is inside the flow control and is basically the same for all pumps. The flow control valve regulates, or controls, the constant flow of fluid from the pump as it varies with the demands of the steering gear. The pressure relief valve limits the hydraulic pressure built up when the steering gear is turned against its stops.
During pump disassembly, make sure all work is done on a clean surface. Clean the outside of the pump thoroughly and do not allow dirt of any kind to get inside. Do not immerse the shaft oil seal in solvent.
If replacing the rotor shaft seal, be extremely careful not to scratch the sealing surfaces with tools.
REMOVAL & INSTALLATION
- Disconnect the hoses at the pump. When the hoses are disconnected, secure the ends in a raised position to prevent leakage. Cap the ends of the hoses to prevent the entrance of dirt.
- Cap the pump fittings.
- Loosen the bracket-to-pump mounting nuts.
- Remove the pump drive belt.
- Remove the bracket-to-pump bolts and remove the pump from the van.
- Installation is the reverse of removal. Fill the reservoir and bleed the pump by turning the pulley counterclockwise (as viewed from the front) until bubbles stop forming. Bleed the system as outlined in the following procedure.
- Fill the reservoir to the proper level and let the fluid remain undisturbed for at least 2 minutes.
- Start the engine and run it for only about 2 seconds.
- Add fluid as necessary.
- Repeat Steps 1-3 until the level remains constant.
- Raise the front of the vehicle so that the front wheels are off the ground. Set the parking brake and block both rear wheels front and rear. Manual transmissions should be in Neutral; automatic transmissions should be in Park.
- Start the engine and run it at approximately 1500 rpm.
- Turn the wheels (off the ground) to the right and left, lightly contacting the stops.
- Add fluid as necessary.
- Lower the vehicle and turn the wheels right and left on the ground.
- Check the level and refill as necessary.
- If the fluid is extremely foamy, let the van stand for a few minutes with the engine off and repeat the procedure. Check the belt tension and check for a bent or loose pulley. The pulley should not wobble with the engine running.
- Check that no hoses are contacting any parts of the van, particularly sheet metal.
- Check the oil level and refill as necessary. This step and the next are very important. When willing, follow Steps 1-10 above
- Check for air in the fluid. Aerated fluid appears milky. If air is present, repeat the above operation. If it is obvious that the pump will not respond to bleeding after several attempts, a pressure test may be required.
The procedures for maintaining, adjusting, and repairing the power steering systems and components discussed in this section are to be done only after determining that the steering linkages and front suspension systems are correctly aligned and in good condition. All worn or damaged parts should be replaced before attempting to service the power steering system. After correcting any condition that could affect the power steering, do the preliminary tests of the steering system components.
The vane type power steering pump is used in Saginaw steering systems. Centrifugal force moves a number of vanes outward against the pump ring, causing a pumping action of the fluid to the control valve.Disassembly
- Clean the outside of the pump in a non-toxic solvent before disassembling.
- Mount the pump in a vise, being careful not to squeeze the front hub too tight.
- Remove the union and seal.
- Remove the reservoir retaining studs and separate the reservoir from the housing.
- Remove the mounting bolt and union O-rings.
- Remove the filter and filter cage; discard the element.
- Remove the end plate retaining ring by compressing the retaining ring and then prying it out with a removal tool. The retaining ring may be compressed by inserting a small punch in the 1 / 8 in.(3mm) diameter hole in the housing and pushing in until the ring clears the groove.
- Remove the end plate. The end plate is spring loaded and should rise above the housing level. If it is stuck inside the housing, a slight rocking or gentle tapping should free the plate.
- Remove the shaft woodruff key and tap the end of the shaft gently to free the pressure plate, pump ring, rotor assembly, and thrust plate. Remove these parts as one unit.
- Remove the end plate O-ring. Separate the pressure plate, pump ring, rotor assembly, and thrust plate.
Clean all metal parts in a non-toxic solvent and inspect them as given below:
- Check the flow control valve for free movement in the housing bore. If the valve is sticking, see if there is dirt or a rough spot in the bore.
- Check the cap screw in the end of the flow control valve for looseness. Tighten if necessary being careful not to damage the machined surfaces.
- Inspect the pressure plate and the pump plate surfaces for flatness and check that there are no cracks or scores in the parts. Do not mistake the normal wear marks for scoring.
- Check the vanes in the rotor assembly for free movement and that they were installed with the radius edge toward the pump ring.
- If the flow control valve plunger is defective, install a new part. The valve is factory calibrated and supplied as a unit.
- Check the driveshaft for worn splines, breaks, bushing material pick-up, etc.
- Replace all rubber seals and O-rings removed from the pump.
- Check the reservoir, studs, casting, etc. for burrs and other defects that would impair operation.
- Install a new shaft seal in the housing and insert the shaft at the hub end of housing, splined end entering mounting face side.
- Install the thrust plate on the dowel pins with the ported side facing the rear of the pump housing.
- Install the rotor on the pump shaft over the splined end. Be sure the rotor moves freely on the splines. Countersunk side must be toward the shaft.
- Install the shaft retaining ring. Install the pump ring on the dowel pins with the rotation arrow toward the rear of the pump housing. Rotation is clockwise as seen from the pulley.
- Install the vanes in the rotor slots with the radius edge towards the outside.
- Lubricate the outside diameter and chamfer of the pressure plate with petroleum jelly so as not to damage the O-ring and install the plate on the dowel pins with the ported face toward the pump ring. Seat the pressure plate by placing a large socket on top of the plate and pushing down with the hand.
- Install the pressure plate spring in the center groove of the plate.
- Install the end plate O-ring. Lubricate the outside diameter and chamfer of the end plate with petroleum jelly so as not to damage the O-ring and install the end plate in the housing, using an arbor press. Install the end plate retaining ring while pump is in the arbor press. Be sure the ring is in the groove and the ring gap is positioned properly.
- Install the flow control spring and plunger, hex head screw end in bore first. Install the filter cage, new filter stud seals and union seal.
- Place the reservoir in the normal position and press down until the reservoir seats on the housing. Check the position of the stud seals and the union seal.
- Install the studs, union, and driveshaft woodruff key. Support the shaft on the opposite side of the key when tapping the key into place.