Why Change your Engine Coolant?
Antifreeze does more than extend the freezing and boiling point of the engine coolant, it lubricates the water pump and provides corrosion protection for the aluminum radiator and engine components. The cooling system should be drained and replenished with new coolant every two years. If a regular schedule is kept, the additional trouble of a system flush is not necessary as minimal deposits will accumulate.
How To Do The Job
Allow two hours for this moderately-difficult job. On the M60 engine it is essential to use the three drain plugs provided to effectively remove the existing coolant. You will need to raise the front of the car at least eight inches such that you can safely work underneath. Do not rely on jackstands, ramps are much safer (or in a pinch, a street curb.) The radiator has a drain plug on the left tank and the engine block has a plug on each side. All are 13mm hex head screws. The engine needs to be cool or cold during this exercise to minimize risk of injury. First, raise the car and remove the coolant reservoir cap.
Remove both splash guards under the engine. The front has four 10mm plastic nuts, the rear has five 10mm steel hex head screws.
Remove the two heat shields attached to the main suspension cross-member. There is one on each side of the sump. Both are attached with four 10mm screws, with one screw each being accessed through a hole in the cross-member. You may have to remove plastic caps to access these. The right-side shield requires deft maneuvering to get it out. Once you figure it out the only thing I can guarantee is that it's twice as hard to get it back in.
A caution at this point: There is a live electrical terminal nearby on the starter which is almost impossible not to touch with the right steel shield while removing or replacing it. Either disconnect the battery or tape over the terminal with three layers of duct tape. This terminal is not fused and can be extremely dangerous if shorted! Do not take a chance.
The drain plugs on the block may have colored paint on them. One can be loosened with a 13mm socket on about a 12-inch extension, the other will need a 13mm crow's foot, or in a pinch a box wrench will do. The first will yield about 2 gallons of coolant, the second just about half a gallon. I used a section of hard vacuum cleaner pipe to aim the coolant into a bucket and minimize spillage.
Remove the plastic drain plug at the left end of the radiator and be prepared to collect about half a gallon of coolant. You may want to switch on the ignition and max the heater controls during this step to improve the chance of draining the heater cores. Take care not to splash coolant in your eyes, and wash them immediately if you do.
Stick the garden hose in the filler opening and squirt a few gallons through to flush out the system.
Clean and replace the block drain screws - apply a non-hardening sealant on the upper half of the threads first, such as Permatex High Tack Adhesive Sealant. Note there are aluminum gasket washers present which I didn't bother to replace. Tighten firmly, a suitable torque value is 20 ft-lbs.
Replace the radiator drain plug and tighten slightly (it doesn't need to be tight to not leak.)
Replace the heat shields and splash guards, and optionally lower the car to the ground.
BMW cars require antifreeze free of phosphates to prevent damage to the aluminum radiator. I would suggest using the factory stuff exclusively, especially if your car is still under the full warranty. The stuff I bought from BMW seems to made in the US anyway, probably "exclusively" to improve their profit margin.
See Prestone's Site See Article from Motor Magazine
Water is mixed 50/50 with antifreeze to make engine coolant (in very cold climates, a higher ratio of antifreeze, say 60/40, may be used.) It's not recommended to use distilled water (per Click and Clack,) but filtered water can't hurt. Add 6.25 liters (6 quarts) of antifreeze to the reservoir first, then fill with water until the system is completely full. There is no bleed screw on this system, and none is required.
The "cold" level is
marked on the tank.