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Fuel Expansion Tank Replacing
 
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Pelican Technical Article:

Fuel Expansion Tank Replacing

Nick Czerula

Time:

3 hours3 hrs

Tab:

$200

Talent:

***

Tools:

10mm sockets, cutting pliers, hose clamp pliers, floor jack, jack stands, wheel chocks, safety glasses, torque wrench

Applicable Models:

BMW X5 Sport Utility (2000-06)

Parts Required:

Fuel expansion tank, hose clamps

Hot Tip:

Be careful when working with evaporator system, do not damage any hoses or connections

Performance Gain:

Repair evaporator system faults

Complementary Modification:

Replace evaporator hoses

The fuel supply system in a BMW E53 consists of:

  • Fuel tank
  • Fuel filler with associated breathing and venting pipes
  • High pressure fuel pump assembly with fuel filter and fuel level senders

The fuel tank is two-lobed. There are two fuel level senders, one in each lobe on the left and right sides underneath the rear seat cushion. The left fuel tank lobe holds the fuel level sender, and the right tank lobe holds the fuel pump.

The fuel expansion tank (liquid / vapor separator) is mounted on the right side up in the wheel.

The expansion tank prevents liquid gasoline from entering the vent line to the charcoal canister. A float assembly inside the separator rises to seal the lines in the event of excess liquid fuel in the tank.

If the expansion tank becomes blocked or plugged, the fuel tank will not be able to breathe properly. Vacuum in the fuel tank is an indication of this. There will be a suction sound when removing the fuel filler cap. You may also not be able to fill your vehicle, as the handle will pop off before the tank is full. This can be due to a plugged vent line, plugged expansion tank or a stuck expansion tank float.

The tank can leak as well, like most evaporator components. Usually you will have a large leak code (P0455) from either a broken hose or broken fitting.

Remember that your car may have been serviced before and had parts 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. Never work on your vehicle if you feel the task is beyond your ability.

Our vehicle may vary slightly from yours as models do change and evolve, as they grow older. 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.

Jack your vehicle and support it using jack stands. See our tech article on jacking up your vehicle. Always wear your safety glasses whenever you're working under your car.

The fuel expansion tank (liquid / vapor separator) is mounted on the right side up in the wheel (red arrow).
Figure 1

The fuel expansion tank (liquid / vapor separator) is mounted on the right side up in the wheel (red arrow).

The tank can leak as well, like most evaporator components.
Figure 2

The tank can leak as well, like most evaporator components. Usually you will get a large leak code (P0455) from either a broken hose or broken fitting. Inspect the hoses and T connectors (yellow arrows). Check that all of the plastic welded nipples are secure and not cracked. I find most of the leaks at the small blue fittings (green arrows). Also, leaks can come from a damaged larger fitting (red arrow). Don't forget to check the fittings on the top of the expansion tank as well.

First remove the right rear wheel well liner.
Figure 3

First remove the right rear wheel well liner. See our tech article on wheel well liners removing. Then cut the three hose clamps off the hoses (red arrows). Once cut, gently open the clamps and remove them from the hoses.

Remove the large hose that the clamps were cut from.
Figure 4

Remove the large hose that the clamps were cut from. Slide the hose straight off. Be careful not to place too much force on the nipple. They will break. If stuck, I use a small pick to pry the hose away from the nipple and spray silicone lubricant between the hose and nipple (red arrow).

Remove the two small hoses (red arrows) that the clamps were cut from.
Figure 5

Remove the two small hoses (red arrows) that the clamps were cut from. Slide the hoses straight off. Be careful not to place too much force on the nipples. They will break. If stuck, I use a small pick to pry the hose away from the nipple and spray silicone lubricant between the hose and nipple.

Next, remove the two 10mm fasteners (red arrows).
Figure 6

Next, remove the two 10mm fasteners (red arrows).

Lower the tank just enough to access the hoses at the top (red arrow).
Figure 7

Lower the tank just enough to access the hoses at the top (red arrow).

Next up, cut the two remaining hose clamps (red arrows), and remove the two remaining hoses.
Figure 8

Next up, cut the two remaining hose clamps (red arrows), and remove the two remaining hoses.

Reverse these steps to install the expansion tank.
Figure 9

Reverse these steps to install the expansion tank. Use new hose clamps. Crimp them using a hose clamp crimping tool (red arrow). Be sure all hoses are installed and orientated correctly. If twisted, the stress can crack a hose or fitting. The hose clamp sizes are 14.5mm for the small hoses and 25.6 mm for the large hoses.

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Comments and Suggestions:
Dan Comments: Could you indicate which hose on the expansion tank goes to where and its function? For example, the large hose attached to the white nipple in Fig. 2 returns liquid fuel back to the fuel tank. I am trying to diagnose a hard to refuel problem. Thanks!
July 28, 2016
  Followup from the Pelican Staff: For trouble filling the tank. Check that the vent line at the canister is not plugged. The larger hoses on the expansion tank have to be clear as well. - Nick at Pelican Parts  

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Page last updated: Mon 12/5/2016 02:51:46 AM