E39 Water Pump Removal reccomendations
Go buy or build a tool to hold the pump pulley wheel AND get a 32mm wrench (thin). Both are available on Ebay for about $45 including shipping. I built the pulley holding tool many years ago for my 1970 BMW2002 and have been using it ever since. My tool just broke on my 540i so I had to rebuild it by drilling two 7/16" holes 38mm apart and a C-shaped cutout between the two bolt holes whose circular diameter is 38mm as well. I bought a piece of iron bar about 2' long and 3/16" thick with a width of about 1". Alternatively, you can take out 1 bolt on the pulley and bolt on a tool with a 6mm (1/4") hole at one end of the same bar dimensions given. Do not expect to be able to undo the 32mm bolt with your normal human stregth alone; you need to use an impact technique to loosen the bolt. This is done using a hammer on the wrench to loosen the bolt while holding the homemade tool (or purchased one). REMEMBER THAT THE BOLT LOOSENS IN THE CLOCKWISE DIRECTION ON THE WATER PUMP PULLEY! Sometimes the bolt has been on way too tight and it took a lot of hammering to get it off. My 540i bolt was way overtightened.
Next. on the California and I assume other US cars, there is an exaust air pipe that goes around the entire front of the engine. A bolt on each side of this air pipe lets it be taken off prior to removing the water pump. The bolts are just an inch or two behind the front plane of the engine on either side of the engine. There are two small o-ring type gaskets on this pipe that must be present upon re-installation.
Before pulling off the water pump, make sure the two metal pipes exiting the rear of the water pump stay in their positions and are not pulled free from their rear connections. I used a channel lock wrench to attempt to hold the smaller pipe in but was unsuccessful. The larger pipe stayed in. I would recommend using two hose clamps mounted on the pipes to provide a place for a screwdriver to be able to keep them back while the water pump is extracted from it's position.
Now, I am waiting for parts...