How To: Disassemble, Inspect, and Rebuild a Saginaw Power Steering Pump

SAATR

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[TUTORIAL]

Tools:


3/8" drive ratchet
3/8" drive SAE socket set (must include 3/8" to 5/8" minimum, up to 1" with 1/2" drive to 1 1/8" is ideal)
3/8" torque wrench, 10lbft-80lbft
10" or 12" adjustable wrench
A selection of flat blade screwdrivers
A seal pick (small flat blade screwdriver works too)
An 1/8" pin punch
A 1/4" pin punch
External snap ring pliers with around 1" of jaw opening (if you have EVO)
Hammers, specifically a ball pein and small dead blow
A large plastic bowl, for cleaning internal parts
A larger container (cutoff 5 gallon bucket, turkey roasting pan) for cleaning dirty, external parts
Wire brush (brass)
Arbor press (optional) - for compressing the rear cover of the pump. A large, 12" C-clamp or a buddy leaning on a hammer handle works too.
A (reasonably clean) workspace, preferably a table.
A 4" PVC sewer pipe coupler to hold the pump while you assemble it.

A smartphone or digital camera - Take pictures of everything! This is good practice and can be the difference between a job well done and a job done twice!

Supplies:

1 Gallon Odorless Mineral Spirits
2 quarts power steering fluid
1 Scotchbrite pad (red or brown)
4 cans brake parts cleaner
1 roll lint free shop towels (cut up old t-shirts work well, too)
1 0.5mL tube of Loctite 545

Parts:

Power Steering Pump Rebuild Kit (Gates 350390 used here)
Dorman 926-049 Steering Bypass Tube (replaces EVO valve and fitting)

Procedure:

**Obligatory Safety Disclaimer**


Safety glasses and nitrile gloves should be considered bare minimum safety gear for this operation. Mineral spirits and brake clean will chew up your hands and skin, and can cause all manner of skin diseases and cancers from repeated contact. Power steering fluid is no different. You'll see my gloved hands at various points in this procedure for that very reason. These chemicals also don't help your vision should they find their way into your eyes. That goes double for flying bits of debris, clips, and springs. Wear your safety glasses!

**End Obligatory Safety Disclaimer**


This should go without saying, but you must begin by removing the pump from the vehicle. That process is not detailed herein, and is left to the mechanic to do the necessary. Once the pump is separated, you should have this:

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A greasy, well worn piece of automotive history that has been seeping fluid since the (second) Bush administration. Take the larger of your two containers and pour about a quart of mineral spirits into it. Remove the bracket from the front of the pump, and the bracket held on by nuts at the rear of the pump, and place them in the mineral spirits to soak. On the back side of the pump, if you have EVO, there is a solenoid retained by two separate snap rings. Remove the snap rings, and the solenoid should slide off the valve like so:

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**The snap ring requiring pliers is not pictured, as it split in two and flew off to parts unknown.. safety glasses, folks!**

Now remove the valve from the pump using the adjustable wrench, a properly fitting socket (1 1/8" deep socket, if you have it), or if all else fails, a hammer and chisel. If you DO NOT have EVO there will be a standard screw-in power steering fitting in its place, which is easily unscrewed. Take care here, as the pressure control valve is behind this fitting and under spring pressure. Once the rear fitting is removed, you'll have this:

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If you are using the Dorman bypass kit or similar, the valve and adapter can be discarded. While sitting on your work surface, tilt the pump on its back. The pressure control valve and spring should fall out of the pump. Put a couple of inches of mineral spirits in your smaller bowl and put the valve and spring in the bowl to soak. Continue by removing the two studs from the rear of the pump, as shown:

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Take note of the location of each stud. Remove them and place them in the larger container. Now pick the pump up by the shaft and, holding it over the work table, tap the sheet metal reservoir with the soft-faced hammer. It should fall off with relative ease. Once apart, put the reservoir in the larger container. You should be left with this:

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The fuzzy looking disc that you see at the 1:30ish position of the pump is a magnet. A very, very dirty magnet. You should only find fine, powdered metal bits on this magnet if all is well. If you find chunks, you're probably not going to be salvaging this pump. Remove the magnet and wrap it in a t-shirt or paper towel, and set it aside. Use the seal pick to remove the three off white colored o-rings seen in the picture and discard.
 
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SAATR

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Note the black sludge that has been wiped off the magnet. Find any chunks larger than this, and you will likely have an issue in the pump or steering gear.

Examine the back side of the pump. The large ring retains the back plate of the pump. To remove it, use a large flat blade screwdriver to push the ring around until one of the ends is close to the hole pictured below.

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Once the ring is properly aligned, tap the 1/8" punch into the hole until it pushes under the ring, like so:

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Starting at the punch, use the large flat blade screwdriver to pry the ring out of groove. Keep the ring covered with one hand at all times, as they can decide to pop all the way out at any time. Once removed, the back cover will pop up slightly due to spring pressure. The back cover can be difficult to work out of the pump due to the tight fit of the o-ring seal. Pushing the cover in with a hammer handle and letting it pop back up under spring pressure can help remove it. Once removed, you will be able to see the spring sitting in the rear pump plate:

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Place the cover, retainer, and spring in the small container. Using the seal pick, remove the rear cover o-ring from the pump housing. Place the pump on its back on the workbench, and inspect the nose of the shaft. Remove any dirt, grease, oil, or rust from the shaft using the wire brush and brake parts cleaner. Polish any heavy rust until smooth. Once the shaft is smooth and clean, use your soft faced hammer to gently but firmly drive the shaft out of the pump. Once the shaft begins to move, the rear pump plate will be free or very close to it. Remove the plate, dowels, vanes, and rotor housing and set them aside. Continue to drive the shaft out of the pump until it is flush with the shaft seal. Switch to the 1/4" pin punch and ball pein hammer. Place the punch at the bottom of the hole in the shaft and drive it out.

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You should have:

1 rear pump plate
1 pump shaft, front pump plate, and rotor assembly
10 vanes
2 dowels
1 pump rotor housing

Place all of these in the small container.
 
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SAATR

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At this point your small container should look something like this:

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All of these parts should be thoroughly washed with mineral spirits, rinsed with brake cleaner, and dried with whatever lint free cloth/towel you have. Lay them out on another clean cloth, and cover them while you're inspecting each. The shaft can be separated from the front pump plate and rotor by removing the c-ring that is around the shaft (2 in the picture)

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Once separated, the front side of the rotor and the front pump plate can be inspected for wear and damage. I had taken several pictures of the front plate, rear plate, and the rotor to show normal wear and some minor damage that I found, but those pictures were lost. Instead I'll use this picture and an *********** of another picture of the rear plate.

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**Note that for a proper inspection, the parts should be clean and totally dry. This plate is neither, but will serve our purposes.**

The first things to look at are the thrust surfaces of the rotor and front and rear plates. The dull grey finish on the machined surfaces is perfectly normal and not a sign of damage or abuse. The polishing in area (1) of both plates AND the rotor is the thrust surface for the rotor and is normal. The lighter, shinier circular area called out by (2) is the swept area of the vanes and is also normal. Note the light grooving in (3) and (4). Given the relative darkness of the metal in the grooves called out by (3), these are most likely machining marks made visible by the polishing of the surfaces. Area (4), however, is actual damage caused by debris passing through the pump. Note the bright color of the metal in the groove. None of the grooving can be felt by the dragging a fingernail lightly across the surface. This generally means that the grooving is less than .001" deep, and for our purposes, inconsequential. The slightly textured finish of the rotor is normal. The edges of the vane slots on the circumference of the rotor and the flat faces should be sharp and free of nicks, dings, or rounding. Cracks in any of these parts mean they are junk.

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This is the rotor housing. The lines going from front to rear one the inner surface are most likely caused by pump chatter. Chatter in a vane pump is usually caused by air pockets in the liquid being pumped. Because air is compressible and power steering fluid is not, pockets of both passing through the pump cause the rotor to accelerate and decelerate rapidly, and these changes in speed and pressure allow the vanes to bounce along the surface of the rotor housing. If this continues, a wavy wear pattern emerges, as seen here. Without any clear guidance from Saginaw on reusability, I will say that given the previous performance of the pump and my past experience with (relatively) low pressure vane pumps, this is not a problem. If this were being used on a unit with Hydroboost, I would be more skeptical due to the higher pressures involved. The circumferential grooves are foreign object damage from debris passing through the pump. Most of these grooves passed the fingernail test, though a few were obviously deeper. In a professional capacity, I would have failed this pump and replaced it, or at least taken that decision to the customer. For my own, known equipment, I chose to run it again.

Finally, we come to the pump shaft.

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The splines that drive the rotor show practically no wear. The two rings visible toward the nose of the shaft were, front to rear, the back edge of the pump pulley and the shaft lip seal. A quick polish with Scotchbrite removed both, and no other imperfections were found.
 
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SAATR

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Shaft after polishing:

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The last internal component to inspect are the vanes. There will be some polished spots on the flats of the vanes, but no gouging or uneven wear. You'll find light polishing on the front and rear edges that face the thrust plates, but no nicks, dings, or gouges. Essentially, if you find no damage to the thrust plate surfaces, there isn't likely to be any damage to the vane surfaces that mate to them. The last thing to check is the edge that contacts the rotor housing. This should be highly polished, as shown on the left. The right side is, of course, the edge that points inward toward the shaft.

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Once you are satisfied that everything is reusable, it's time to prep the pump housing. First, remove the pump shaft lip seal. Insert a large flat blade screwdriver between the housing and the metal portion of the seal as indicated by the arrow. Twist the screwdriver to push the seal up. If your screwdriver spins, get one with a wider blade. Once the seal has been pushed up all the way around, pry up on it to remove it.

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Wash the housing and all external items thoroughly with mineral spirits and the wire brush.

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Rinse the parts with brake cleaner, and blow out all ports and orifices with compressed air, if available. Wipe the inside of the housing out with a cloth, and make sure the shaft bushing is clean and free of grime. Inspect the bushing for damage. The bore should be smooth to the touch, with a spiral groove for lubrication. Look for straight lines that run from one end of the bore to the other, sure signs of damage during shaft removal. Your kit should include a new bushing if the old one is damaged. If it passes the visual inspection, lubricate the bushing bore and shaft with clean power steering fluid and install the shaft in housing. Move the shaft side to side to check for play. If none is found, remove the shaft and set aside. Open your installation kit and remove the new shaft seal. Position the shaft seal in the bore, taking care to make sure the seal is sitting even to the housing bore all the way around. Use a piece of flat steel or wood as a driving tool, and drive the seal into the bore until the tool contacts the pump housing.

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SAATR

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The fully seated seal should look like this:

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Take the pump housing and place it, shaft side down, in your PVC coupler. Reassemble the shaft/plate/rotor/clip assembly that you took apart during inspection. Lubricate the shaft bushing, shaft, thrust plate and rotor with clean power steering fluid and install the shaft in the housing. This is not as straightforward as it may seem, as the shaft can bind during installation and require judicious... wiggling to free up. Gentle taps with the soft faced hammer can help when it's stubborn. Once the shaft is fully seated in the housing, align the dowel holes in the front pump plate with the dowel holes in the housing as shown.

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Install the dowels in the housing. Next, lubricate and install the rotor housing. The dowels go in the SMALLER of the two sets of holes. Be sure to install the housing in the same orientation that it was originally installed. My rotor had the three diamond marks facing the rear of the pump, like so:

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Next, lubricate and install the pump vanes with the POLISHED edge to the OUTSIDE. Then, lubricate and install the rear pump plate o-ring in position (1) shown here:

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Followed by the rear pump plate:

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Place one face of your soft faced hammer on the rear pump plate, and push down on the hammer head with your body weight until the plate seats on the rotor housing.
 
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SAATR

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Next, install the rear pump plate spring

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Followed by the pump body cover o-ring in position (2) from earlier. Then, place the pump body cover in position, as shown:

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**The magnet should be installed in the position shown in the picture. Do not forget it!**

This is where an arbor press is an extremely handy thing to have. The cover has to be pressed in place, overcoming the compression of both the sealing o-ring and the spring. It then has to be held there while the retaining ring is worked into place, like this:

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I'm using the screwdriver to make sure the ring is fully seated in its groove. Once that is accomplished, the pump will look something like this:

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Gather the remaining o-rings from your kit. The assortment should look like this:

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O-rings (1) and (2) are for the 3/8" threaded holes at the rear of the pump. (3) seals the pump to the reservoir at the discharge port. (4) seals the front of the pump to the reservoir, and is not pictured. (5) goes on the adapter that threads into the discharge port. (6) (7) (8) aren't used in this application, as they don't fit the lines or any other connection to the pump, including the EVO valve.
 
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This shows the installed positions of o-rings (1) through (4). Using a seal pick or small screwdriver as shown, slide the tool between the seal and the pump body for one or two revolutions to remove any twist the o-ring may have gotten during installation. Lubricate all o-rings with power steering fluid.

If you haven't already, thoroughly clean the fluid reservoir at this time. If you HAVE already cleaned it, do it again. Rinse thoroughly with brake parts cleaner, and wipe the internal surfaces until the rag comes back clean. Get a good work light or flashlight and inspect every crevice for dirt, dust, or lint. The #1 killer of all hydraulic systems is contamination, followed closely by lack of maintenance. There are no filters on this system, so it will only ever be as clean as it is when newly assembled.

Once you are absolutely certain the reservoir is clean, with the pump shaft down in the PVC pipe, lubricate the o-ring sealing surfaces of the reservoir with clean fluid and position the reservoir on the pump body. The three holes in rear of the reservoir should align with the 3 o-ringed holes in the pump. Once the ports are as closely aligned as possible, install the two (clean) studs in their respective threaded holes, as shown:

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The studs will act as both guides and installation tools. Push down on the reservoir with one hand, and evenly tighten the studs with the other. Once the studs are as tight as you can get them by hand, push down on the reservoir with both hands to fully seat it. Remove the studs and inspect the seals below them. Sometimes the o-rings around the holes can be twisted or pinched, as shown:

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You have two options here: 1) Use a small flat blade screwdriver or other tool and gently push the o-ring back into position. If everything was well lubricated, it should move back fairly easily. If it won't move, or you aren't comfortable doing it, then 2) you can remove the reservoir and install it again, paying special attention to the alignment of the ports. Once the reservoir is properly installed, the studs torque to a range of 25lbft to 40lbft. I split the difference (roughly) and torqued mine to 32lbft.

Now we come to the pressure regulating valve. The valve installs in the pump discharge port (as marked a couple of photos back) and, as the name implies, regulates output pressure of the pump. It will come out as a single spool valve, but you will notice a threaded plug on one end. When (carefully) removed, you will find all of this hidden inside:

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Removing the plug is no mean feat. I had to clamp the spool body in a vice between two blocks of wood to get enough grip to turn the plug. Upon further inspection, I found locking compound on the plug's threads. All of this was washed, rinsed, dried, and reassembled. No burrs or scratching were found on the ball or seat, though some wear was evident on the spool body itself, which is expected. I used a generic equivalent to Loctite 545 on the plug threads, and reinstalled to a torque of "snug+", lacking an official spec.

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SAATR

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This is the fully assembled pressure regulating valve. It, along with the large spring, go in the pressure regulating valve port called out in a previous post. The spring is installed first, then the valve with the flat end out. To be absolutely clear, the valve is installed plug end first, with the flat side facing out. Once that's done, all that remains to be installed is the EVO valve or the line adapter, whichever you have. I opted to delete the EVO system and picked up this kit from Dorman:

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It includes everything shown here. All you need to do is lubricate the threads and o-ring with clean power steering fluid and install it in the discharge port. Torque is, again, 25lbft to 40lbft. Screw the 180 degree tube into the adapter, install the bracketry that was removed during disassembly, and install the pump.

If you choose to retain the EVO valve, you'll need to source new o-rings to seal the valve to the 180 degree adapter that came on the truck. As far as I know, these are unobtainable outside of a GM dealer, and I didn't like EVO enough to go through the hassle and delay.

[/TUTORIAL]
 
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