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Water Pump Replacement
 
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Pelican Technical Article:

Water Pump Replacement

Nick Czerula

Time:

3 hours3 hrs

Tab:

$100

Talent:

****

Tools:

Set of sockets, wrenches, screwdrivers, two M6 bolts

Applicable Models:

BMW Z3 (1996-02)

Parts Required:

Water pump, hoses, engine coolant

Hot Tip:

Work with a cool engine.

Performance Gain:

Car will cool down again

Complementary Modification:

Change serpentine belt, radiator hoses.

BMW Z3 cooling system components include:

  • Radiator and coolant overflow tank.
  • Belt driven coolant pump bolted to the front of the engine block.
  • Belt driven fan attached to front of coolant pump. Viscous clutch controls fan speed based on engine temperature and rpms.
  • Electric (auxiliary) cooling fan attached to front of radiator. The cooling fan is controlled by the engine control module (ECM) via an output final stage.
  • Electrically heated thermostat.
  • Automatic transmission cooler or heat exchanger (if equipped).
  • 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 hoses 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 water pump, but a good starting point. 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. 

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 water pump on BMW Z3's 4 and 6-cylinder models. Be sure to work with a cool engine and confirm the cooling system lacks pressure before opening.

Do not remove the expansion tank cap or work on any other part of the cooling system while the engine is hot. Coolant or hot steam may escape and will scald you. To do any work on the cooling system, wait until the engine has cooled off.

To avoid marring the paint and trim, work with a plastic prying tool or wrap a screwdriver tip with masking tape before prying out body or interior items.

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 you're 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. Do you have 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.

Remove the engine cooling fan and shroud. See our tech article on radiator cooling fan replacing.

Models with 4-cylinder engine:
Before removing engine drive belt, loosen four 10mm water pump pulley fasteners, do not remove yet.
Figure 1

Models with 4-cylinder engine: Before removing engine drive belt, loosen four 10mm water pump pulley fasteners, do not remove yet. (green arrows). Remove engine drive belt. See our tech article on engine drive belt on replacing. You only have to remove the alternator belt. Just be sure to clean any coolant residue off the A/C belt with dish soap and water once the repair is completed. Remove four 10mm water pump pulley fasteners.

Next remove water pump pulley from water pump.
Figure 2

Models with 4-cylinder engine: Next remove water pump pulley from water pump. While the pulley is off, inspect it for small cracks or damage. The pulleys can fail, although not that often. Usually least when we expect it.

Remove three 10mm water pump mounting fasteners (green arrows) and one 6mm Allen fastener (yellow arrow).
Figure 3

Models with 4-cylinder engine: Remove three 10mm water pump mounting fasteners (green arrows) and one 6mm Allen fastener (yellow arrow). When removing the Allen fastener, use a fast sharp loosening action the first time you attempt to loosen it. The bolt is long and requires a good jolt to break it free. Be sure your Allen bit is fully engaged in the bolt before removing it.

The water pump sits deep in the timing cover and it can be tough to get the sealing O-ring to pass through.
Figure 4

Models with 4-cylinder engine: 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 M6 bolts into to extract water pump. To remove water pump from timing cover, thread two M6 bolts (green arrows) into the top and bottom of water pump. Use a ratchet to evenly tighten, one turn per side, then switch and tighten opposite side, repeat until water pump O-ring has cleared timing cover.

Once water pump O-ring has cleared timing cover, you can remove it by hand.
Figure 5

Models with 4-cylinder engine: Once water pump O-ring has cleared timing cover, you can remove it by hand.

Once the water pump has been removed, clean the O-ring rubber from the water pump housing.
Figure 6

Models with 4-cylinder engine: Once the water pump has been removed, clean the O-ring rubber from the water pump housing. This will ensure the O-ring will seal properly.


Before installing new water pump, thoroughly clean water pump mounting surface and check for debris inside water pump cavity, (inside timing cover).

Lubricate water pump O-ring with coolant and install in 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 threads in the engine. Install water pump pulley and tighten fasteners. Install engine drive belt, cooling fan shroud, and fill and bleed cooling system. Once complete, check cooling system for leaks and top up cooling system. 

Models with 6-cylinder engine:
Before removing engine drive belt, loosen the four 10mm water pump pulley fasteners, do not remove yet.
Figure 7

Models with 6-cylinder engine: Before removing engine drive belt, loosen the four 10mm water pump pulley fasteners, do not remove yet. Remove engine drive belt. See our tech article on engine drive belt on replacing.

Now you can remove the four 10mm water pump pulley fasteners.
Figure 8

Models with 6-cylinder engine: Now you can remove the four 10mm water pump pulley fasteners. (green arrows)

Next, remove water pump pulley from water pump.
Figure 9

Models with 6-cylinder engine: Next, remove water pump pulley from water pump. While the pulley is off, inspect it for small cracks or damage. The pulleys can fail, although not that often. Usually least when we expect it.

Remove four 10mm water pump mounting nuts.
Figure 10

Models with 6-cylinder engine: Remove four 10mm water pump mounting nuts. (green arrows)

The water pump sits deep in the timing cover and it can be tough to get the sealing O-ring to pass through.
Figure 11

Models with 6-cylinder engine: 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 M6 bolts in to extract water pump.(green arrows)

To remove water pump from timing cover, thread two M6 bolts into sides of water pump.
Figure 12

Models with 6-cylinder engine: To remove water pump from timing cover, thread two M6 bolts into sides of water pump. (green arrows)

Use a ratchet to evenly tighten, a few turns per side, then switch and tighten opposite side, repeat until water pump O-ring has cleared timing cover.
Figure 13

Models with 6-cylinder engine: Use a ratchet to evenly tighten, a few turns per side, then switch and tighten opposite side, repeat until water pump O-ring has cleared timing cover. (green arrows)

Once water pump O-ring has cleared timing cover, you can remove it by hand.
Figure 14

Models with 6-cylinder engine: Once water pump O-ring has cleared timing cover, you can remove it by hand.


Before installing new water pump, thoroughly clean water pump mounting surface and check for debris inside water pump cavity, (inside timing cover).

Lubricate water pump O-ring with coolant and install in 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 water pump pulley and tighten fasteners. Install engine drive belt, cooling fan shroud, and fill and bleed cooling system. Once complete, check cooling system for leaks and top up cooling system.

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Page last updated: Sat 12/3/2016 02:07:19 AM