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Thermostat Replacement
 
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Pelican Technical Article:

Thermostat Replacement

Nick Czerula

Time:

3 hours3 hrs

Tab:

$100

Talent:

****

Tools:

Set of sockets, wrenches, screwdrivers

Applicable Models:

BMW E46 M3 Coupe/Conv (2006)
BMW Z4 Coupe/Conv (2006)

Parts Required:

Thermostat, hoses, engine coolant

Hot Tip:

Work with a cool engine

Performance Gain:

Car will cool down again or restore function of heater

Complementary Modification:

Change radiator hoses

Maintaining the cooling system so that the engine does not overheat is a significant step toward getting engine longevity. There are many components in the BMW Z4 cooling system:

  • Radiator and coolant overflow tank
  • Belt driven coolant pump bolted to the front of the engine block
  • Electric cooling fan attached to front of radiator - The cooling fan is controlled by the engine control module (ECM) via an output final stage
  • 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

BMW Z4 S54 6-cylinder models utilize a mechanical thermostat. This tech article covers the S54 engine thermostat.

Other 6-cylinder models utilize an electrically-heated engine thermostat. The engine control module (ECM) controls and monitors operation of the thermostat. If a fault occurs a code is stored in the ECM, usually with the description "Map cooling circuit". A fault code can be present yet the vehicle will lack any cooling system issues, such as overheating. If you have this fault code, replace your thermostat and bleed your cooling system. Other symptoms of a faulty thermostat are engine overheating, engine slow to warm up and lack of heat.

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.

BMW Z4 S54 6-cylinder models utilize a mechanical thermostat (red arrow).
Figure 1

BMW Z4 S54 6-cylinder models utilize a mechanical thermostat (red arrow). This tech article covers the S54 engine thermostat.

Working at the throttle position sensor, press the wire release tab (red arrow) and pull the electrical connector straight off.
Figure 2

Working at the throttle position sensor, press the wire release tab (red arrow) and pull the electrical connector straight off.

To remove the upper hose: using a flathead screwdriver, loosen the upper radiator hose clamp (red arrow).
Figure 3

To remove the upper hose: using a flathead screwdriver, loosen the upper radiator hose clamp (red arrow). Once loose, slide the hose clamp away from the radiator. Then disconnect the hose by pulling it straight off the thermostat housing.

To remove the lower hose: using a flathead screwdriver, loosen the lower radiator hose clamp (red arrow).
Figure 4

To remove the lower hose: using a flathead screwdriver, loosen the lower radiator hose clamp (red arrow). Once loose, slide the hose clamp away from the radiator. Then disconnect the hose by pulling it straight off the thermostat housing.

Next, open and unclip (red arrow) the wire harness mount and remove the harness (green arrow) from the mount.
Figure 5

Next, open and unclip (red arrow) the wire harness mount and remove the harness (green arrow) from the mount.

Next, you have to remove the three 10mm thermostat fasteners (red arrows).
Figure 6

Next, you have to remove the three 10mm thermostat fasteners (red arrows).

Remove the support bracket (red arrow) from the thermostat housing.
Figure 7

Remove the support bracket (red arrow) from the thermostat housing.

Use a pry bar (red arrow) and gently lever the thermostat housing toward the radiator until the sealing O-ring for the rear pipe (green arrow) is visible.
Figure 8

Use a pry bar (red arrow) and gently lever the thermostat housing toward the radiator until the sealing O-ring for the rear pipe (green arrow) is visible.

Remove the thermostat housing from the engine by lifting it straight up.
Figure 9

Remove the thermostat housing from the engine by lifting it straight up.

Remove the thermostat (green arrow) from the engine by pulling it straight out of the housing (red arrow).
Figure 10

Remove the thermostat (green arrow) from the engine by pulling it straight out of the housing (red arrow).

Use a small pick and remove the sealing O-ring (red arrow).
Figure 11

Use a small pick and remove the sealing O-ring (red arrow). Replace it with a new one. Install the new thermostat and evenly tighten all the fasteners. Install the radiator hoses, and replace the hose clamps. Fill and bleed the cooling system. Remember to check the cooling system for leaks, and top up the coolant when complete.

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Page last updated: Wed 12/7/2016 02:59:50 AM