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Replacing the Power Steering Pump:

I just replaced my pump this past weekend. It's definitely doable, but not exactly what I would call easy :)

I used this tool to remove and reinstall the pulley:

This is the correct pump

Napa also has the serpentine belt for our trucks and can look it up in their computer. About $60 for the good one belt, $40 for the cheap one.

You will need a 13/16" wrench to turn the pulley puller. It's an odd size, but that's what it takes. Get the LONGEST one you can. You're going to need the leverage. The end of the puller also needs to be held in place, but I honestly forget the wrench size. It was something I had in my normal wrench set. Bottom line, make sure you check what wrenches you need to operate the puller before you get started.

The correct puller shaft is the one that has the skinny rod stuck in the end of it. You'll recognize it when you see it. The puller collar has two curves available. make sure you use the tighter curve on the pulley. The wider curve is not small enough and won't do the job.

You don't need to leave the belt on in order to pull the pulley off since you'll be turning the puller against itself and holding both components of it with your wrenches. So pull the serpentine belt off. Inspect and be prepared to replace it if necassary. If you haven't pulled the belt off before, it's a piece of cake. You need a 1/2" drive ratchet wrench. On the passenger side of the engine at the top is the belt tensioner. It has a square hole that your 1/2" drive ratchet wrench will fit into. You'll also notice some hashmarks on the tensioner. The little arrow should be between the hash marks. If it's not, or if the belt is cracked/worn, time to replace it. Just put your ratchet wrench in the hole, crank down on it and the belt will come off nice and easy. Reverse to reinstall.

I don't know how your pulley will be, but mine was TIGHT. It was very hard to get it off. Make sure you have gloves and/or a long wrench to save your hands. It fought me until the last milimeter. Don't give up. It's hard, but doable. Well, mine was, yours might come off like greased llightning.

After the pulley is off, get under the truck and remove all the hoses. There are two low pressure lines held on with hose clamps. The hose clamp screws have hex heads. I found it easier to use a screwdriver with a hex bit than it was to use a flat head. Once you get the hose clamp backed off, grip the hose in your fist and work it off the barb. If you decide to use a flat head to pry the end of the hose to get it started, keep in mind that the end of the hose butts up against a lip on the metal input tube. So you'll need to work the screwdriver between the lip and the hose. If your pump/hoses are gunked up, it won't be obvious when you look at it.

The high pressure line should come off pretty readily with a 1" (I think) open end wrench right on the flat back of the pump. Even though I have the original pump and it was pretty gunky, mine came off with no problem at all.

You should be able to remove all of these lines from under the truck. As you remove each one, fluid will leak out. Just set a bucket under it and give it a few minutes. After all of the hoses are disconnected, remove the power steering reservoir cap to let air in so the rest of the fluid can drain out.

After you have all the hoses disconnected and pushed out of the way, take off the two nuts on the back of the pump (from underneath of the truck). These hold the pump to the bracket. Then remove the nut on the bracket where it's held to the engine block. That should release the hose clamp that's holding your block heater cord in place. Next, you need to remove the stud that actually holds the power steering pump bracket in place.

Once the rear bracket is off, remove the lowest bolt on the front of the power steering pump from underneath of the truck.

Next, get up on top again and remove the top two bolts that go through the front bracket and hold the pump in place. At this point, the pump should be free to pull out the top of the truck.

Once you get the pump out and finish juggling it around in your power steering fluid covered hands to drain the last of the fluid out...there are three things to unbolt before it will come out of the reservoir.

The two studs sticking out of the back of the pump are double sided studs like the one that was in the engine block holding the rear bracket in place. Just unscrew them. Next, you need to pull out the high pressure fitting that is on the back of the pump. Mine wasn't on there too tight. Don't mind the spring and valve that fall out when you remove the fitting. You won't need those since the new pump comes with them.

With those three things removed, the pump should be relatively easy to push out of the front of the reservoir. Clean up the reservoir real good. Marvel at the metal shavings stuck to the magnet on the old pump.

On the new pump, unscrew the high pressure fitting on the back, but be mindful of the spring and valve, you need them! Leave the plastic plug in the fitting, you'll take that out later. Make sure you keep everything clean! Place the included magnet in a similar location as on the old pump. Make sure the o-rings are in place. I recommend moistening them with some power steering fluid.

Press the new pump in the old (clean) reservoir, reinstall the studs and high pressure fitting (don't forget to put the spring and valve back in place). Clean up the truck as best you can (hoses, ground underneath, etc) so you can more easily spot leaks once you're done installing the pump.

This is a good time to play with your pulley tool and make sure you know how to reinstall the pulley when it's on the truck. In the kit that I referenced above, you'll use the installer nut, and the skinny bolt that is loose in the kit (not the one with the threadless nub at the end of it). You'll need to run the wide/flat bolt up to the top of the skinny bolt, then run the skinny bolt through the pulley and into the center of the power steering pump shaft. Screw it into the shaft as far as it will go, then back it off a few turns. Now you're ready to crank the flat nut down and press the pulley onto the pump. Don't over do it while you're playing, though. No sense in having to remove the pulley twice :)

Mounting the pump is the reverse of pulling it out. Start with the twp front bolts from above. Just get them started, don't tighten them down so you can shift the pump a little. Get underneath and install the rear bracket, but leave it loose as well. Install the bottom bolt on the front of the pump from underneath. That should be all the nuts and bolts in place holding the pump in place. Now tighten down the front bolts (from above and underneath), then do the rear nuts and stud. Don't forget to reinstall the hose clamp that holds the block heater cord to the stud in the block.

Now reinstall your hoses. I started with the high pressure line, but do whatever works for you. Make sure the high pressure line is tight, but don't over crank it.

After all the hoses are connected, time to install the pulley. As I described above, start the pulled on the power steering pump shaft. You do NOT need to hold the end of the center bolt, just turn the flat nut. But you'll notice that the shaft starts to turn. No problem, you have enough mechanical advantage to hold the pulley with one hand as you turn the wrench with the other. But only for a little bit. Just get it started so the pulley is snug. Remove the tool.

Install the serpentine belt. Now reinstall the tool on the pulley and shaft. The belt will hold the pulley in place as you push the pulley onto the shaft. It should be a lot easier to do than the install. I highly recommend using a gear wrench for this part of the job. It takes a 9/16" gear wrench. I used one with no offset and it worked great. Save a lot of time. You'll know when the pulley is completely installed because the end of the shaft will be flush with the pulley and you will not be able to turn the flat nut any further.

If you left the center bolt backed out a few turns, you should be able to very easily remove the pulley installer tool with your fingers. If it got tight, the 9/16" wrench fits the end of the center bolt as well.

Now all you have to do is fill the reservoir and purge the system of air. The "right" way to do it is to fill the reservoir to the "cold" fill line. Jack both wheels off of the ground and turn the steering wheel to full lock left-right 40 times. Check the fluid, refill as necassary, repeat.

What I did was fill the reservoir to the cold fill line, start the truck for a few seconds, turn it off, check the fluid. Fill as necassary, repeat. Then, with the truck running, turn the wheels to full lock left-right 5 times, turn it off, check the fluid, repeat. When no more foaming or no more fluid is needed, turn it at least ten times lock to lock and recheck.

As it turns out, I didn't have to add any more fluid at all after I initially filled up the reservoir.

Make sure you check for leaks every time you check the reservoir.

Sorry if this is too detailed or long. But I wish someone had provided these directions for me before I started this weekend. It's definitely doable by a shade tree mechanic. The hardest part about it is removing the pulley. The rest is pretty straight forward.

Oh, and the reason that I changed my pump is because whenever I turned the wheel or used the brakes, I got a bad pulsing in the brakes or steering wheel. Verified there was no air in the system. I believe it was the pressure release valve in the pump. Regardless of what the problem was, the problem was within the pump and everything is 100% with the new pump.

Good luck!


My truck is a 98. It does not have a remote reservoir.

With respect to how long it took me to type it versus doing have no idea how hard it was to get that pulley off, lol. I think I put a total of 6 hours into the R&R of that pump. I probably could have shaved two hours off total if I tried.

Regarding upgraded reason why I bought my Hummer instead of modding some other vehicle is because I've raced enough to see how expensive mods are. Not the initial mod, but the costs incurred by the damage done to parts that weren't designed for the "enhanced" part. I've done a lot of off-roading, most people who've been around the Hummer community have seen me on the trails, maybe even been on some trails that I've led. So I'm not talking completely out of my rear, maybe only part way ;)

If a power steering pump puts out more power, I'd be concerned about the impact on the steering gear and power brake booster. I'd also be concerned about how it affects a mile marker that was designed for less pressure. However, it could be that the mile marker was designed for more pressure, I don't know. I do know that the rest of that hydraulic system was designed for the pump that's in there. I don't doubt that there will be some immediate advantages to the increased power output of the upgraded pump. I would just be concerned about reliability in the long term. I've done a lot of crazy things with my truck and I've never felt like I needed more hydraulic pressure to do them.

To each their own. You also have to remember that I just spent 6 hours replacing my pump with a stock pump. It's not as if I would be excited about doing it over so I can put in an upgraded pump :)


I have changed about 6 to 10 pumps in my 10 year Hummer career. It is a job that I do not look forward to. :-(

Hazards include: (1)You can break the stud off of the exhaust manifold (pretreat with penetrating oil). (2) You can beak the aluminum bracket if it does not seat evenly onto the engine front as you wrench it. So tighten the lower bolts a little, go up top and tighten the upper bolts a little ... walk it in.

I remove the pump from the truck first and then take the pulley off at the bench. I use a similar pulley remover. I also use a HUGE ratchet to help me. The pulleys are really pressed on.

Getting the pump body out of the case can be a challenge. I have learned to loosen the two case bolts on the back up about 1/2 inch, remove the large nut which retains the spring and piston, then use a soft mallet to pound the body out (hitting the case bolts) while supporting the case on its 1/4 inch lip using several 2 x 4's.

Removing air from the system is critical. This has been covered in the HML over the years. To reiterate. Lift the front of the truck off the ground. Fill the PS reservoir, with the engine off, turn the steering wheel lock to lock (fully clockwise and fully counterclockwise) at least 20 times. Then, replace the lost fluid in the reservoir, start the engine for under 30 seconds. Again, fill the reservoir. Start the truck while still lifted, turn the steering wheel lock to lock about 20 times. Finally, lower the truck to the ground, check the fluid, start it and turn the steering wheel lock to lock about 20 times.

Two people make this job relatively easy, one person .... PITA! Doing it in the field .... MISERY!


I have the puller but the fan is right in the way to get it to work. I pulled the fan bolts off to make room but the fan won't come out due to the shroud. I dont have to pull the shroud do I?

You remove the pump from the truck and change pulleys at the bench.


While this would be ideal, some setups do not allow the pump to come off with the pulley in place. You might have to remove all of the belt-driven accessories on that side of the truck, plus some, just to get the bracket loose.

If you have the fan off, you can tie it up or lay it down inside the shroud to get enough clearance.

Dave B.

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