How do you replace the water pump on a 1997 Seville SLS with the Northstar engine?

First off, locate a GM water pump socket just for this type of pump. Auto Zone will loan you one of these sockets for about $40 and refund the full price when you return the socket after using it to remove and replace the water pump.

Before removing the water pump be sure to clean and flush your system. Be sure to turn the heater on full heat setting to allow the coolant to run through the heater hoses too. Get a quart of the flush clean out the coolant system. This is very important on aluminum engines. It will run cooler and also your new pump will last longer and the warranty won't be void from leaving dirty coolant in the system.

I got a flush connector to hook up the garden hose and give it a thorough flush after running the cleaner through for 20-3- minutes. It may take a while to get all of the cleaner out of your system so take the time and watch for bubbles in a 5 gallon pail. Once the bubbles stop forming after 4-5 full buckets filled using the radiator tube extension you can be certain that the cleaner is out and just fresh water is left.

Once you are through cleaning and flushing the system Ssart by removing the black plastic flap panel that covers the headlights. Remove the fuse panel cover on the fender. Unplug the connector to the air box.remove the air cleaner all the way down to the bottom case that holds the air cleaner. It sits on 2 plastic pegs and lifts right off. Once you have the air cleaner and intake tube removed take off the motor mount strut bar and both brackets. If this piece is worn out you will need to replace it as well. Make a list as you take things apart so you can get new parts to replace the worn ones. The bolt with the hose connected to it if removed will have to have sealant applied to it during reassembly.

Remove the top radiator hose and tuck into the grill opening.

You will see the pump on the drivers side of the engine toward the front right behind the driver's side fan. If you need more room you can remove this fan by taking out the two top bolts and removing the top transmission line to the radiator and pushing it aside. As you pull up the fan remove the electrical connector. The fan is now out of the way. Remove the bottom radiator hose then loosen the 3/4" hose connections.

You can remove more parts to gain better access but this is not really necessary. You can remove the motor hanging bracket and the EGR tube if you feel it's necessary.

Locate the four small bolts on the water pump plate and remove them with a combination of 10mm sockets, ratchets and extensions. The lower bolt will be easier to loosen than it will be to remove without dropping it. Be very careful to only unscrew until it's loose then use a magnet to pull it out of the cover. Another trick is to use a short piece of hose to push over the bolt and then use it to unscrew the bolt and remove it without dropping it. If you do drop it and can't find it just get a new one at the hardware store. You can get the clear plastic hose there as well. heat the hose with a hair dryer to make it pliable if necessary to fit over the head end of the bolt. I found this short hose technique to be the easiest to reinstall these bolts when the time is right.

Moving on, now that you have the water pump cover plate removed you can use the special GM socket to remove the water pump. Make sure the socket is located over the vanes of the pump and seated between the tabs of the old pump. Insert a 1/2" ratchet or a breaker bar and use a length of pipe to turn the pump clockwise. This is the righty-tighty direction which will loosen the pump from the housing. This is opposite of the lefty-loosey direction since the pump rotates in the reverse direction so as to not accidentally loosen the pump if the bearing seizes prematurely.

The socket will turn the pump about 30 degrees and then you should be able to just pull the pump out of the housing. Notice the smaller tab with the notch at the top. You will have to line the new pump up the same way it came out so that the drain hole is located properly when reinstalling the new pump. Be sure to remove the O-ring from the groove and clean up any residue from the groove. Make sure to remove the groove ring and clean out the groove completely with a small knife and a wire brush.

I like to run a tap through all of the bolt holes to clean out the corrosion before installing the new gaskets and sealer. Be sure to blow out the freshly tapped holes once cleaned out.

If you don't have a tap that is this size get a longer bolt at the hardware store that is the same thread size and grind or file several notches into the end of the bolt. This will be sufficient to remove any buildup and clean out the existing threads for reassembly. It's a poor man's tap but it works and is cheap and easy to come by.

Use a wire brush, maybe even several styles of wire brushes to clean up all of the parts including inside the hose ends. Inspect carefully and replace any hoses that are cracked, frayed or worn out.

This is a good time to pour 2 gallons of distilled water into the upper radiator hose to flush out the mineral water left in it. Also pour another gallon of distilled water into the radiator fill tank to purge the mineral water from that part of the system as well.

Put sealer on the round O-ring and insert it into the circular groove in the water pump housing before installing the new water pump. Be sure to place the small tab with the notch 30 degrees to the right of top center. This will ensure that the tab is at the top once you seat the new pump with the special GM socket.

You will probably need a long breaker bar or a pipe on the end of the 1/2" ratchet in order to seat the pump properly. Make sure that the fingers on the special socket are engaged properly before exerting pressure on the pipe to the ratchet. If you have applied sealant properly this will help you to turn the pump counter-clockwise into the seated position. Check carefully that the bent tabs on each tab are located against the housing properly and you are finished with this stage of installation. With a steady, even pressure the new water pump should seat firmly when it locks in.

I found that installing the new thermostat into the cover before installing the cover to the water pump housing makes it easier to make sure that the thermostat is centered properly. Tighten according to specs for this size bolt. Do not strip the aluminum by over tightening.

Now put some sealer into the funny shaped groove and seat the new funny shaped O-ring. At first the O-ring will seem too large but keep working it into the groove with your thumbs and you will soon make it seat in the groove properly. Now push the 3/4" fitting into the hose and align the water pump plate with the holes on the water pump housing. The 3 easy bolts should be started first but not tightened until the 4th bolt is started as well. Use the clear plastic flexible tubing/hose to hold the head of the bolt to start the bolt into the hard to reach hole. You will have to move the wire assemblies around to get at this. These wire assemblies will be very stiff because of their size and age but they do move out of the way. Move the lower radiator hose one way or the other to allow access to start and tighten these bolts.

Tighten the bolts gradually a few turns at a time to seat the O-ring properly. Once snug, torque to specs for this size bolt, Do not over tighten or strip these bolts or you will have leaks.

Once you have the pump in place you can install the radiator hoses and make sure the clamps on all of the hoses are tight.

Replace the air tube and air cleaner. Be sure to reconnect the electrical connector to the air box. Replace the motor mount strut and brackets then lastly the headlight flap panel.

The heater should be set on high heat so that coolant flows through the heater hoses and doesn't trap air in the system.

Start the engine and then add GM Dex-Cool coolant. This is the only kind to use or you will void all warranties! Add slowly so that you allow room for the air to leave the system. You may have to shut off the engine and restart several times before the coolant is free of air. Add 2 full gallons of new coolant if you have extremely cold winters. Then top off the system with distilled water as needed. Recheck daily until you are certain that the system is full and free of air and has the correct cooling and low freeze temp.

Check for leaks. There shouldn't be any. To be sure, park in a dry area and let the engine idle for 5 or 10 minutes. Move the car and if it's dry you have done a good job in replacing your own water pump on a 1997 Cadillac NorthStar Engine.