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Coolant Expansion Tank Replacement
 
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Pelican Technical Article:

Coolant Expansion Tank Replacement

Nick Czerula

Time:

1 hour1 hr

Tab:

$200

Talent:

**

Tools:

7mm socket, flathead screwdriver

Applicable Models:

R56 MINI Cooper Hatchback (2007-11)
R56 MINI Cooper S Hatchback (2007-11)

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 the radiator hoses and flush the cooling system

The MINI R56 cooling system is filled through the plastic coolant expansion tank (or coolant reservoir) at right front of the engine compartment. There is no cap on the radiator. Other components of the cooling system consist of:

Belt driven coolant pump bolted to the right side of the engine block.

Turbocharged engines: Electric coolant pump bolted to the left front of the engine block.

Turbocharged engines: Engine oil cooler attached to oil filter housing.

Electric cooling fan attached to rear of radiator. The cooling fan is controlled by the engine control module (ECM) via an output final stage.

Electrically heated thermostat.

Automatic transmission cooler (heat exchanger).

Coolant temperature sensor at cylinder head.

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

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.

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.

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

The coolant expansion tank is located on the left (driver) side of the engine compartment (red arrow). The vent hose (green arrow) enters the right side of the tank.

Using a pair of hose clamp pliers, remove the vent hose clamp (green arrow).
Figure 2

Using a pair of hose clamp pliers, remove the vent hose clamp (green arrow).

Pull the vent hose straight off (red arrow).
Figure 3

Pull the vent hose straight off (red arrow).

Then remove the tank fastener (red arrow).
Figure 4

Then remove the tank fastener (red arrow). Use a 7mm socket or nutdriver.

Once the fastener is removed, unclip the tank from the radiator support by angling the back up as you unclip the front (green arrow).
Figure 5

Once the fastener is removed, unclip the tank from the radiator support by angling the back up as you unclip the front (green arrow).

Lift the tank enough to access the hose at the bottom (red arrow).
Figure 6

Lift the tank enough to access the hose at the bottom (red arrow). Using a flathead screwdriver, release the hose retaining clip (green arrow). Lever the clip up until it reaches the stop.

Then pull the coolant hose off the coolant expansion tank.
Figure 7

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. Both are made of plastic.

When installing the expansion tank, connect the bottom hose first.
Figure 8

When installing the expansion tank, connect the bottom hose first. The retaining clip is properly seated when an audible click is heard. Be sure to align the mounting pin (red arrow) with the radiator support (green arrow). The radiator support should have a rubber grommet in the bore indicated by the green arrow. I come across quite a few of these missing. If you lose yours or it is missing, you can get a new one for a few dollars. If not installed or missing, the expansion tank will rattle, possibly damaging a hose or cracking the tank. Then install the upper hose and fasteners and reroute the hoses as they were before. Fill and bleed the cooling system. Once complete, double check all the hose connections and check the engine for coolant leaks.

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