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I just want to give some incite regarding how to replace the power steering pump in the '05 STS, which may be the same going into 2007 up to perhaps 2009. Many have complained that it's difficult to impossible to remove the high pressure side connection, so they end up looking for advice or bringing their STS to a garage. I just replaced my pump today. Here are the steps: 1. After removing the engine left and middle plastic covers, remove the air filter cover, air filter, and inlet duct leading to the throttle body. (Note: make sure to remove the MAP sensor harness first) Notice that once the above is removed you will be able to clearly see the high side connection; 2. Drain the power steering fluid reservoir. Be aware that there will still be residual fluid. After draining, if the cap is placed back on the reservoir it will hinder fluid draining. 3. Remove the serpentine belt from the pump. Use a breaker bar and insert the socket end into the square hole on the tensioner pulley and pull or push towards the driver's side fender thereby releasing tension on the belt. 3. Disconnect the fluid reservoir from the engine by removing the two 10mm nuts that secure it (Note: Unless you have an air tool, you will have to remove the reservoir, so you can at least get it out of the way); 4. Believe it or not, the pump pulley does not necessarily have to be removed before removing the pump; however, if you plan on removing the high pressure side without an air tool, then I suggest removing the pulley first. To remove the pulley, you will have to rent or purchase the right tools, such as Wilmar W87022 GM Power Steering Pump Pulley, which is low end, but will do the job. If you don't know how to use the pulley tools, I suggest you watch a couple of Youtube videos. 5. Once the pulley is removed it's time to remove the high pressure side connection. You will have to rent or buy an 18mm crowfoot wrench. Do not use this! Instead, buy one like this! Notice the second one has 4 sides and the top is partially closed. This is the type that will provide the necessary leverage needed to remove the nut. The first one will likely slip under high torque and could possibly round off the nut. Then I suggest that you buy a 3/8 socket wrench extension set, such as an inexpensive Stanley or this Bostich locking extension set, which is what I purchased at Walmart and must say I like it. Also, keep handy a couple other 3/8 extension bars that you may already have. I was able to remove the high pressure nut by using a 1/2 breaker bar with a 3/8 adapter, along with enough extension bars to raise the breaker bar above the engine while the crow foot wrench is securely on the nut. The reason I said to remove the power steering fluid reservoir is because it will be in the way of having a straight line up from the nut. Once the pulley and reservoir is out of the way, you will have a comfortable straight line down to the nut and accordingly can place the crowfoot on the nut and apply the necessary torque using a breaker bar. Once the crowfoot is securely on the nut you need to apply slow even and increasing torque on the nut until it breaks loose. If you have the crowfoot on correctly and have a comfortable straight line leading up to the breaker bar, you should be able to apply the necessary torque to break the nut loose--even if you have to use some of your body weight in a controlled manner until the nut breaks loose. 6. Once the high pressure side nut is removed, you should then remove the pump. (Note: There will be a small bracket with a 10mm nut that secures the high pressure line to the pump. Don't worry about it until you remove the two (2) 16mm bolts that secure the pump). One is easily removed from the front, but the other is on the left (driver's side) of the pump, which is bolted to the engine. Use a flashlight if need to see it. It's a little awkward to get at but you will be able to get a socket on it with a short extension. You may also be able to unscrew it by hand as well. 7. Once the pump is removed use a 10mm combination wrench to remove the nut that secures the high side line to the pump or a small 1/4-inch socket wrench. Gently pull the pump forward a little to get easy access to the nut. If you buy a inexpensive 1/4 socket set with a small socket wrench (the El cheapo $5 set you can buy at Home Depot, you can use it here because it's small and convenient). 8. Once the pump is removed, notice the bracket needed to secure the left side bolt may not come with your new pump. It's secured with 3 bolts to the back of the pump. You may need to transfer it to the new pump. 9. When it's time to install the new pump there are some things to be aware of: i) thread the high pressure line into the new pump first because you will be able to maneuver the pump whichever way necessary to cleanly thread the nut; ii) absolutely make sure you know which side of the pulley is the front (facing you), which is the side that has the fitting/lip necessary to pull the pulley off. I suggest you mark the front of the pulley with a strip of black electrical tape or something, so you don't make the mistake of getting tired and installing the pulley backwards--like I did. I installed the pulley 2/3 of the way backwards and finally figured out what I did after it wouldn't go on any further. I was tired and my brain locked up which left me open to making this silly mistake. I ended up having to use my breaker bar by putting the bar behind the pulley on the left side and pulling it forward--applying high pressure and rotating the pulley many times and repeating this process until it came off. After bending the pulley in numerous places, I then bought a used pump with a pulley. I pulled the used pulley and gave it another successful try after learning a lesson; iii) when installing the pulley, you have to make sure the top of the pulley hole is flush with the top of the pump shaft. To understand what I mean, take a look at the pulley and pump shaft and note how far the pulley is on the shaft--you will see it's flush; and iv) the tool needed to put the pulley on may be awkward to work with because the bolt that is threaded into the pump shaft may loosen. You do not want that bolt to loosen to the point that it eventually is barley hanging on, which means it may pull out of the pump shaft which will strip the outer threads. So be aware of this and make sure the bolt is not unscrewing as you are pressing the pulley on the pump. The shaft threads are 3/8 in. x 16 NC. 10. Once the pump is on, it's time to secure the reservoir and hoses put everything back together. I would take note of the high pressure side rubber hose to determine if it should be replaced. It's inexpensive, so this would be a good time to install a new one. Also, note whether the new pump is blasts holes into the power steering lines. If the lines are deteriorated the new pump may supply more pressure than the worn out lines are capable of handling. 11. Bleed the system by removing the low pressure side line and fill the reservoir to the FULL COLD level. Raise both wheels of the front end and put on jack stands or use two heavy duty jacks. With the reservior filled with fluid to proper level, turn the steering wheel fully back and forth 12 times, making sure fluid remains filled to proper level. Afterwards, reconnect the low side line. Start the engine and note whether there is any indication of air such as noise or whining. If so, repeat the bleeding procedure. This is the process which the GM's 2006 STS factory Service Manual provides (See Volume 1, page 2-10).