BMW X3 models utilize cooling system components which consist of:
Radiator and coolant overflow tank.
M54 and 6-cylinder engines: Belt driven coolant pump bolted to the front of the engine block.
N52 engines: Electric coolant pump bolted to the right front of the engine block.
Electric cooling fan attached to rear of radiator. The cooling fan is controlled by the engine control module (DME) via an output final stage.
Automatic transmission cooler (heat exchanger).
Heater valve and heater core (for climate control).
Coolant level sensor inside expansion tank.
Coolant temperature sensor at cylinder head.
Radiator outlet temperature sensor.
Coolant hose and lines.
When a water pump begins to fail, you'll notice that the car tends to overheat at low engine speed, such as sitting at a stoplight. When you accelerate, the engine temperature will drop. Now, this is not always indicative of a broken water pump, but it's a good starting point when diagnosing the problem. You may also want to try squeezing the top radiator hose with the engine warmed up and running. You should feel pressure build up on the back of the hose and surge once it is released. If you feel no pressure, it's a fair bet that the water pump is failing. On the belt-driven water pump, sometimes you can also see a slight drip coming from the water pump housing itself. These weep holes are cast into the pump housing and allow excess coolant to drain out if it has leaked past the various seals in the pump. The bearing can fail creating a grinding noise or creating free-play in the shaft also resulting in a coolant leak.
In this article, I'll go over the steps involved with replacing the belt-driven water pump on BMW X3 6-cylinder M54 engine models.
Be sure to work with a cool engine and confirm the cooling system lacks pressure before opening the cooling system.
Keep in mind that when your car was serviced before, parts may have been replaced with different size fasteners used in the replacement. The sizes of the nuts and bolts we give may be different from what you have, so be prepared with different size sockets and wrenches.
Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. If working with the electrical system, disconnect the battery before beginning. Always catch fluids in appropriate containers and properly dispose of any fluid waste. Recycle parts, packaging and fluids when possible. Do not work on your vehicle if you feel the task is beyond your ability.
Vehicle models change and evolve as they grow older, so the vehicle shown in our illustrations may vary slightly from yours. If something seems different, let us know and share your info to help other users. Questions or want to add to the article? Leave a comment below. When leaving a comment, please leave your vehicle information.
Drain the cooling system. See our tech article on cooling system draining and filling. Before doing any work on the cooling system, wait until the engine has cooled off.
Remove the engine cooling fan. See our tech article on radiator cooling fan replacing.
The water pump (red arrow) on M54 6-cylinder engine models is located at the front of the engine. It is a belt driven water pump, unlike the late model X3s with electric water pumps. A faulty water pump may cause noise or a leak from the weep hole (yellow arrow). Pressure test the cooling system to be sure the pump is faulty. See our tech article on cooling system leak testing.
Locate the accessory (main) drive belt tensioner, then locate the 16mm HEX boss (yellow arrow). Using a ratchet with a long handle and an 16mm socket (green arrow), rotate the drive belt tensioner clockwise to release the tension. When tension is relieved, place a 7/32 pin or drill bit in the small hole (red arrow) above HEX boss to hold tensioner in position for belt removal.
Next, remove the water pump pulley from the water pump (red arrow). While the pulley is removed, inspect it for small cracks or damage. The pulleys can fail, although not that often--usually when we least expect it.
The water pump sits deep in the timing cover and it can be tough to get the sealing O-ring to pass through. There are two threaded holes you can install M6x1 bolts in to extract the water pump (green arrows). To remove the water pump from the timing cover, thread the two M6x1 bolts into the sides of the water pump. Use a ratchet to evenly tighten a few turns per side. Then switch and tighten the opposite side. Repeat until the water pump O-ring has cleared the timing cover. Once the water pump O-ring has cleared the timing cover, you can remove it by hand. Before installing the new water pump, thoroughly clean the water pump mounting surface and check for debris inside the water pump cavity (inside timing cover). Lubricate the water pump O-ring with new coolant and install it in the engine. Hand tighten the fasteners in a crisscross pattern slowly. Tighten one a few turns, then the next and so on. The water pump will slowly draw into the engine. Be careful not to work too quickly, you could strip the stud threads. Install the water pump pulley and tighten the fasteners. Install the engine drive belt, cooling fan, and fill and bleed the cooling system. Once complete, check the cooling system for leaks and top up the cooling system.