Replacing the waterpump on VN onwards Commodores is a fairly straight forward job that can be done in an hour or so and without any special tools. One thing to keep in mind though is that being a Buick engine the bolts that secure the waterpump to the block are imperial so a 3/8 and 1/2 inch socket will be needed.

Most times a waterpump leak will be easy to spot on these engines, with the engine running coolant will be seen dripping around the area of the harmonic balancer however if you are not 100% sure the waterpump is at fault I suggest having a pressure test of the cooling system carried out first. NOTE – Do not do this job with a hot engine! Wait until it has completely cooled down.

The first step of removing the cooling fan is not absolutely necessary, however for the small amount of time it takes it does make the job soooo much easier. The cooling fan is secured to the radiator by four 10mm bolts and has one electrical connection to undo (blue arrow). The bottom bolt on the drivers side is a little tricky as it is under the charcoal cannister but is easily removed with a 10mm socket, 3 inch extension and ratchet.(Notice the crack in the radiator tank on the r/h picture – not good!)

Once you have the four bolts removed and the electrical connection undone it will take a little bit of maneuvering and the fan and shroud will be out of the way. Our next step is to loosen the four 10mm bolts that hold the waterpump pulley on. The bolts are very close to the hub of the waterpump and a thin-walled socket is best for removing these. If you have to use a open ended spanner for these be careful not to round the heads off.

Once you have these bolts loosened it is time to remove the drivebelt. An 18mm spanner is needed here, however if you only have a 19mm you can CAREFULLY use the open end to release the belt tension.

Removing the belt from the waterpump pulley first is the easiest way to remove it. If you are not confident of the layout of the belt I suggest drawing yourself a diagram before removing the belt. Next we can remove the four loosened pulley bolts and remove the pulley. Now we can see the 3/8 and 1/2 inch bolts that need to be removed. A word of caution with the smaller 3/8 bolts, the threads often have a lot of corrosion around then and can be very tight. Take your time and work the bolts backwards and forwards to avoid snapping them off.

There are two dowel pins that locate the pump and a light tap with a hammer should loosen it enough to be removed.

Now comes the fun part of removing the old gasket. Be sure to remove all of the old gasket – there is nothing worse than having to do a job twice! I find that a single-sided razor blade is best for doing this. I also suggest cleaning the bolts up with a wire wheel if you have one or a wire brush. Failing these, a piece of sandpaper can come in handy to clean the bolts.

Time to check the new waterpump with the old one just to be sure the guy down at the auto parts shop has done his job correctly. Take the gasket out and apply some ‘gasket goo’ to both sides. You can now sit the gasket in place on the two locating dowels and then with waterpump in one hand and the bolts in the other you can sit the pump in place and start winding in the bolts.

Tighten the bolts, being careful not to overtighten the smaller 3/8 bolts. All the bolts only need to be nipped up with a bit more tension on the larger 1/2 bolts.

The reassembly steps are as follows -
Fit the waterpump pulley and hand tighten the four bolts. Refit the drivebelt by fitting it to all the pulleys except the waterpump one, push the tensioner down and slide the belt on to the waterpump pulley.

DON’T FORGET to now tighten the four 10mm bolts securing the waterpump pulley.

Refit the cooling fan ensuring that the electrical connection gets plugged in. Refill the cooling system, turn the heater dial to hot and let the engine reach operating temperature, check for any leaks and ensure that the cooling fan comes on and shuts off. Allow the engine to cool and check the coolant level in the reservoir. All done!