Withdrawal
Disconnect the ground wire from the battery.
Drain the coolant from the engine.
Remove fan.
Loosen the belt pulley bolts. While doing this, hold and press the V-belt so that the pulley does not turn.
Remove V-belt.
Unscrew the 4 bolts securing the belt pulley and remove the belt pulley from the hub.
Pull up the toothed belt guard.
Compress the tension spring of the toothed belt tensioner and wedge the tension pin with BMW tool 115010, if necessary, you can make such a clip yourself.
Loosen and push back the hose clamps. Disconnect water hoses from pump.
Loosen 3 fixing screws (on M40/M50/M51 engines - 4 bolts) and remove the water pump.
1 pump
2 Corps
3 Pump bearing
4 Retaining ring
5 flange
6 Seal
7 Slip ring seal
9 Impeller
10 Bolt
M50 engine: Screw 2 M6 threaded screws into the threaded holes -arrows-, pressing the water pump evenly away from the engine. Do not skew the pump. On the 4-cylinder M40 engine, proceed in the same way, but here the threaded holes are located vertically.
Installation
All engines except M50: Completely scrape off seal residues from surfaces with a scraper.
M50 engine: Remove forcing bolts. Replace water pump O-ring and coat with silicone grease.
Install the water pump with a new gasket and tighten the bolts evenly to 22 Nm.
Loosen the tensioning pin of the toothed belt tensioner without disturbing the free rotation of the water pump.
Install the toothed belt guard.
Connect water hoses and secure with clamps.
Screw on the belt pulley.
Install and tighten the V-belt.
Tighten the belt pulley mounting bolts to 9 Nm while holding the pulley from turning with the V-belt.
Install fan.
Pour coolant into the engine.
Connect ground wire to battery.
Warm up the engine and check the tightness of the water pump and hose connections.