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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:

$200

Talent:

***

Tools:

Set of sockets, wrenches, screwdrivers

Applicable Models:

BMW X5 (2000-06)

Parts Required:

Expansion tank, radiator hoses, engine coolant

Hot Tip:

Work with a cool engine

Performance Gain:

Car will cool down again, coolant leak repaired

Complementary Modification:

Change radiator hoses and flush cooling system

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. In this tech article I will show you to replace the expansion tank and test and replace the coolant level sensor.

Remove the engine splash shield. See our tech article on splash shield removing. Also refer to our article on safely jacking up your car and installing jack stands. Wear those safety glasses whenever you're working under your car.

Drain the cooling system. See our tech article on cooling system draining and filling. You do not have to drain the cooling system completely, just enough to lower the level to drain the expansion tank. You can also clamp off the coolant hoses to prevent leaking coolant when removing the expansion tank.

Remember that coolant is very toxic, especially to pets. If you spill any coolant, rinse it off thoroughly with water. Don't expose pets to any coolant whatsoever.

The coolant expansion tank is located on the left side of the engine compartment (green arrow).
Figure 1

The coolant expansion tank is located on the left side of the engine compartment (green arrow).

Working at the side of the coolant expansion tank, locate the two lower coolant hoses (green arrows).
Figure 2

Working at the side of the coolant expansion tank, locate the two lower coolant hoses (green arrows). Using hose clamping pliers (yellow arrow), clamp off both coolant hoses.

Working at the top of the coolant expansion tank, using a flathead screwdriver, release the upper hose retaining clip by prying up.
Figure 3

Working at the top of the coolant expansion tank, using a flathead screwdriver, release the upper hose retaining clip by prying up. Lever the clip up until it reaches the stop (green arrow).

Next, remove the upper hose from its mounting points on the tank (green arrows).
Figure 4

Next, remove the upper hose from its mounting points on the tank (green arrows). Then remove the upper hose from the coolant expansion tank by pulling it straight off. You may have to wiggle the hose a bit to get it to move free. Be careful not to damage the hose or the tank. Both are made of plastic.

Working at the side of the coolant expansion tank, using a flathead screwdriver, release the hose retaining clips (green arrow) by prying up.
Figure 5

Working at the side of the coolant expansion tank, using a flathead screwdriver, release the hose retaining clips (green arrow) by prying up. Then pull the coolant hose off the coolant expansion tank. You may have to wiggle the hose a bit to get it to move free. Be careful not to damage the hose or tank. To reiterate, both are made of plastic.

Then remove the two 10mm mounting fasteners (green arrows).
Figure 6

Then remove the two 10mm mounting fasteners (green arrows).

Lift the expansion tank up to detach it from the rubber mounting grommet (yellow arrow).
Figure 7

Lift the expansion tank up to detach it from the rubber mounting grommet (yellow arrow). Working at the bottom of the coolant expansion tank, disconnect the electrical connector by pressing the release tab and pulling it off (green arrows).

If your new expansion tank does not come with a level sensor (green arrow) you will have to transfer it over.
Figure 8

If your new expansion tank does not come with a level sensor (green arrow) you will have to transfer it over. Rotate the sensor 45 degrees counterclockwise then pull it straight out of the tank. When installing the new expansion tank, connect the coolant level sensor electrical connector. 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. Then install the fasteners and reroute the hoses as they were before. Fill and bleed the cooling system. Once complete, double check all hose connections and check the engine for coolant leaks.

If you have a check coolant level message and your coolant level is OK, you may have a faulty level sensor or wiring.
Figure 9

If you have a check coolant level message and your coolant level is OK, you may have a faulty level sensor or wiring. Press the right side stalk (green arrow) to toggle through messages (yellow arrow) as needed.

To check the circuit, start by disconnecting the electrical connector (green arrow).
Figure 10

To check the circuit, start by disconnecting the electrical connector (green arrow). Then jump the two terminals together (inset). When jumped, the coolant message should go out. This would indicate a faulty sensor. If the message does not go out, see the following step. Be sure the expansion tank level float is not stuck. If it is, it may not activate the sensor when the coolant level is full.

If you jumped the connector and the check coolant level message does not go away, check the wiring from the sensor to the lighting control module.
Figure 11

If you jumped the connector and the check coolant level message does not go away, check the wiring from the sensor to the lighting control module. You will want to grab a repair manual with the wiring for your specific model. The brown wire should be close to zero volts (0.1 volts). This wire is the ground. The brown wire with the colored tracer (may vary) should be about 3.5 volts. If the ground is not present, try adding a ground to see if that remedies the issue. If the signal reference voltage is not present, you will have to run a new wire to the module or check for voltage out of the module.

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Comments and Suggestions:
Greg Comments: Does this tank have the floating pop up dipstick?
November 30, 2016
Rdg Comments: Hey, I just spent a full day replacing coolant hoses, as I was filling up the coolant and putting the cap on , the float switch disintegrated, can it be replaced for alone or do I need a new expansion tank ? 2003 BMW X 5 4.4
Thanks, Rick
September 23, 2016
  Followup from the Pelican Staff: The float is part of the tank. The sensor can be replaced separately. - Nick at Pelican Parts  
bill Comments: what about the thermostat dose it come out easily and will the car run cool without it
June 24, 2016
  Followup from the Pelican Staff: What vehicle are you working on, what are you trying to fix? - Nick at Pelican Parts  

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Page last updated: Fri 12/9/2016 02:24:03 AM