As usual with my blog, this is not a how-to. It's a you-can. There are plenty of forum posts and blog entries elsewhere that will tell you everything you need to know to complete this maintenance.
I started with an order of parts from ECS Tuning.
- Genuine BMW Remanufactured Water pump #11517838118
- Genuine BMW Radiator #17102228941
- Genuine BMW Thermostat #11531318274
- Water pump gasket #11517831099
- Thermostat O-ring #11531318402
- Water pump O-ring #11537830709 (qty 2)
- Coolant pipe O-rings #11537830712 (qty 2)
To start I removed the lower engine shield, fan with clutch, fan shroud, intake filter housing, hoses, belts, and finally the radiator. The lower radiator hose was impossible to get loose from the rad so I left it in place and removed both through the bottom of the car. You have to move the oil cooler out of the way but you can leave it attached. Support it with something so it's not hanging by the oil hoses.
When removing the thermostat housing there's a coolant pipe that runs between the housing and the bigger pipe that runs to the back of the engine. It's about 2 inches long and machined from aluminum. It is sealed with O-rings (#11537830709) on both ends. Mine pulled free from the engine end, not the thermostat housing end, and thus the whole housing was too big to remove from the space it occupies. I had to work for quite a few minutes to get the pipe loose from the housing side so I could remove it. Most write-ups I've seen don't tell you to remove that pipe at all, but there is an o-ring on the engine end that you should replace as well, so it's just as well that it came out that way.
Once the thermostat housing and thermostat are out of the way, you can unbolt the water pump. A firm pull disengages the pipes on the back side and it easily comes out.
At this point I assessed where I was and decided I needed a few more parts to do a more thorough job. Again from ECS, I ordered:
- Radiator Fan Clutch #11527831619
- Aux fan switch O-ring #13621433077S
- Expanding rivet (qty 4) #17111712963
- Heater hose #64216902679
- Heater hose #64216902680
- Hose #64216902678
- Air filter #13721730946
- Cooling fan blade #11521712058
Once I had the hoses replaced, everything went back together quite quickly. Access to the cooling system on the M3 is very good and doesn't require many contortions (except for those three hoses under the intake manifold). While I was in there, I also replaced the main serpentine belt tensioner spring and pulley. I had bought them a long time ago so they are not listed in the parts list above. The bolts that hold the water pump to the block should be tightened to 7 lb-ft of torque. That is NOT VERY MUCH. I don't even have a torque wrench that will read that low. I used a 1/4-inch ratchet and very gently torqued these bolts down. The bolts that hold the pulley to the water pump snout are also torqued to 7 lb-ft. Be careful!