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Coolant Expansion Tank Replacement
 
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Pelican Technical Article:

Coolant Expansion Tank Replacement

Nick Czerula

Time:

2 hours2 hrs

Tab:

$100

Talent:

***

Tools:

Set of sockets, wrenches, screwdrivers

Applicable Models:

BMW Z4 Convertible (2003-06)
BMW Z4 Coupe (2006)

Parts Required:

Expansion tank, engine coolant

Hot Tip:

Work with a cool engine

Performance Gain:

Car will cool down again, coolant leak repaired

Complementary Modification:

Change radiator hoses, Expansion tank mounting bracket, flush cooling system

BMW Z4 cooling system components include:

  • Radiator and coolant overflow tank
  • Belt driven coolant pump bolted to the front of the engine block
  • Electric cooling fan, DME controlled
  • 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
  • Coolant hoses and lines

When a coolant expansion tank ages it becomes brittle and develops hairline cracks. Inspect your expansion tank every time you change your oil. Look for cracks or any signs of leaks. Ignoring a small crack is a bad idea, as they can grow rapidly and create a major coolant leak before you know it. The coolant level sensor is located in the bottom of the tank. If you have a low coolant level message, but your coolant level is OK, you may have a faulty sensor. When a coolant expansion tank begins to fail a leak may develop at a plastic seam or connection point.

In this tech article I will show you how to replace the expansion tank and replace the coolant level sensor. Be careful when working with ethylene glycol coolant. It is poisonous and especially dangerous for pets. Clean all spills immediately and rinse the area with water.

Do not remove the expansion tank cap 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.

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.

The coolant expansion tank (red arrow) is located at the left front strut near the brake master cylinder.
Figure 1

The coolant expansion tank (red arrow) is located at the left front strut near the brake master cylinder. When replacing, you only have to partially drain the cooling system to remove the coolant from the reservoir and the associated hoses. Drain the cooling system. See our tech article on cooling system draining and filling. Working at the expansion tank, remove the cap. Remove the intake air housing. See our tech article on intake air housing replacing.

Working at the side of the expansion tank, use a small flathead screwdriver and lever the hose retaining clip (red arrow) up until it reaches the top (green arrow).
Figure 2

Working at the side of the expansion tank, use a small flathead screwdriver and lever the hose retaining clip (red arrow) up until it reaches the top (green arrow).

Unclip the hose from the front of the tank and set it aside.
Figure 3

Unclip the hose from the front of the tank and set it aside. Then remove the two 10mm tank fasteners (red arrows). Once released, remove the hose from the tank by pulling it straight off (green arrow).

Loosen the firewall strut brace 16mm fastener (green arrow).
Figure 4

Loosen the firewall strut brace 16mm fastener (green arrow). Remove the strut tower strut brace fastener (red arrow). Lift and lay the strut brace aside (inset).

Working at the bottom of the expansion tank, use a small flathead screwdriver and lever the hose retaining clip (red arrow) up until it reaches the top.
Figure 5

Working at the bottom of the expansion tank, use a small flathead screwdriver and lever the hose retaining clip (red arrow) up until it reaches the top. Once released, remove the hose from the tank by pulling it straight off.

Remove the two 10mm fasteners (red arrows).
Figure 6

Remove the two 10mm fasteners (red arrows). Lift the coolant expansion tank (reservoir) up enough to access the electrical connector (green arrow). Disconnect the coolant level sensor electrical connector at the bottom of the expansion tank. Then remove the expansion tank from the vehicle.

Be sure that the lower mounting grommet (red arrow) was not misplaced or came loose during the removal process.
Figure 7

Be sure that the lower mounting grommet (red arrow) was not misplaced or came loose during the removal process.

To remove the coolant level sensor, rotate the sensor 90° counterclockwise and pull it straight out (red arrow).
Figure 8

To remove the coolant level sensor, rotate the sensor 90 degrees counterclockwise and pull it straight out (red arrow). When installing the expansion tank, connect the coolant level sensor electrical connector. Then install it and tighten the fasteners. Next connect the lower hose to the expansion tank. The retaining clip is properly seated when an audible click is heard. Connect the upper hose and engage the retaining clips until an audible click is heard. Fill and bleed the cooling system. Once complete, double check all of the hose connections and check the engine for coolant leaks.




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Comments and Suggestions:
tom Comments: my vehicle doesn't appear to have a sensor hook up. i don't know if that is normal or not
August 12, 2016
  Followup from the Pelican Staff: it could be. - Nick at Pelican Parts  

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Page last updated: Fri 12/9/2016 02:55:04 AM