Fan clutch: remove with a skinny 32 mm or 1-1/4" open end wrench per Photo-1 & Photo-2. Wack the end of the wrench with a large mallet -- note that it is a left-hand thread. The nut will now unscrew. If the pulley slips, tighten the alternator belt & push the belt down to take up slack & smack it again. If it still slips, you can sacrifice the belt & clamp a pair of vise-grips on it just ahead of the pulley & replace the belt with a new one. There is also a BMW tool to hold the pulley to keep it from rotating. Store the fan clutch vertically if reusing. I used a cheapie wrench from a discount tool supply & cut it down to 1/4" thick with a flycutter on a mill. One could use a grinder but that takes a while. You might be able to get a skinny wrench at a bicycle shop. Alternatively, you can remove two of the adjacent 6 mm hex screws on the fan pulley to make room for a large crescent wrench.
Thermostat: Drain the radiator, plug is on lower left corner of the radiator on the engine compartment side. Remove the 4 screws shown in Photo-3. Install the new thermostat with the pointed end facing forward as shown. There is a small arrow stamped into the brim of the thermostat, install it oriented upward. Put a little vaseline on the o-ring to hold it in place & to seal it well & re-install the housing. Install the radiator drain plug & add coolant to the overflow tank. Squeeze the front hoses to "burp" the air out of them & unscrew the vent screw (8 mm head) in the top of the thermostat housing until a good stream of coolant comes out, & tighten. I do this with the engine cool & off. You might want to repeat this after driving a few miles after it has cooled down again. If it has trouble bleeding, check for blockage in the small return line from the top of the radiator to the coolant tank (thanks to Thomas Meacham for this one). With the system cool, Remove the Radiator Cap. Start the engine and look straight down into the Coolant Tank opening. If you see a stream of coolant about 1/8" ( 3 mm ) diameter returning to the Coolant Tank then everything is OK. If not, then you will experience trouble bleeding the system next time. New thermostats are available from J.A.C., Zygmunt's, etc., approx. $13.75 + s/h.
Additional note: The thermostat housing on the M50 requires not only the o-ring on the new thermostat, but a second small gasket as well. The black plastic thermostat housing contains another coolant passage, so check with the dealer or parts supplier to make sure you have all the required parts for the job. Also, BMP supplies a metal thermostat housing which is a highly recommended replacement for the plastic one when changing thermostats. Thanks to Spots Williams of the e34 board for bringing the missing gasket info to light.
Alternate tip, also thanks to Thomas Meacham: you might be able to do the job without draining the radiator if you keep the overflow coolant cap on. Coolant loss should be minimun & merely top off what leaks out & bleed per above.
gale, 92 735i
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