Affiliate link disclosure – The BMW Repair Guide uses affiliate links in their site. For more information on affiliate links, please click here.
Repair Summary
This article covers replacing the coolant expansion tank (coolant reservoir) in a BMW E60/E61 5 series and E63/E64 6 series vehicle. Even though we used a 2005 645ci to perform this repair, this article can be applied to any 2004-2010 5 or 6 series vehicle with minor modifications.
See all vehicles this article applies to
E60 5 Series M5
E60 5 Series 523Li
E60 5 Series 550i
E60 5 Series 545i
E60 5 Series 540i
E60 5 Series 535d
E60 5 Series 530xi
E60 5 Series 530xd
E60 5 Series 530Li
E60 5 Series 530i
E60 5 Series 530d
E60 5 Series 525i
E60 5 Series 525xi
E60 5 Series 525Li
E60 5 Series 525d
E60 5 Series 523i
E60 5 Series 520i
E60 5 Series 520d
E60N 5 Series 550i
E60N 5 Series 525xi
E60N 5 Series 540i
E60N 5 Series 535xi
E60N 5 Series 535i
E60N 5 Series 535d
E60N 5 Series 530xi
E60N 5 Series 530xd
E60N 5 Series 530Li
E60N 5 Series 530i
E60N 5 Series 528xi
E60N 5 Series 530d
E60N 5 Series 528i
E60N 5 Series 525Li
E60N 5 Series 525xd
E60N 5 Series 525i
E60N 5 Series 525d
E60N 5 Series 523Li
E60N 5 Series 523i
E60N 5 Series 520Li
E60N 5 Series 520d
E60N 5 Series 520i
E61 5 Series 550i
E61 5 Series 530d
E61 5 Series 545i
E61 5 Series 535d
E61 5 Series 530xi
E61 5 Series 530xd
E61 5 Series 525i
E61 5 Series 530i
E61 5 Series 525xi
E61 5 Series 525d
E61 5 Series 523i
E61 5 Series 520d
E63 6 Series M6
E63 6 Series 630i
E63 6 Series 645Ci
E63 6 Series 650i
E64 6 Series M6
E64 6 Series 645Ci
E64 6 Series 650i
E64 6 Series 630i
A BMW coolant expansion tank replacement in your 2004-2010 5 and 6 series car is an easy repair that can keep you from being stranded on the side of the highway or dealing with a blown cylinder head gasket.
If there is an "Achilles Heel" on older (10 years plus) BMWs, it's failure of the coolant system...most notably the coolant expansion tank. The coolant expansion tank (also known as the BMW coolant reservoir) is a molded plastic part that is under constant heat and pressure. After years of this abuse, the plastic expansion tank can become brittle and fail. When a BMW coolant reservoir fails you will know it; it is usually a loud bang followed by steam and fluid being ejected from the hood of the car. Not a pretty sight.
If you are on the road and this happens, pull over immediately and shut the vehicle down. Even driving for a short time with a failed coolant tank will result in a blown cylinder head gasket, and the demise of your vehicle (unless you need a parts car parked in your backyard).
The BMW E60/E61 5 series and E63/E64 6 series both use the same coolant expansion tank. The only difference is the 8 cylinder N62 models have an extra coolant hose attached to the coolant reservoir. We show you both tank configurations in the repair steps below.
Many owners do not wait for failure to perform a BMW coolant expansion tank replacement. In fact, the BMW Repair Guide recommends a BMW coolant expansion tank should be replaced every ten years/100,000 miles for regularly driven vehicles.
View the detailed parts diagram for this repair.
Includes detailed part diagrams, part numbers and links to purchase all of the required components needed to complete this repair.
Before starting this repair, you must have the following required parts.
All BMW E60/E61 and E63/E64
The coolant expansion tank in your vehicle gives additional fluid a place to go after expansion and contraction from temperature change. Because it is subjected to such drastic changes on a regular basis, it can often crack or break. You want to keep all the coolant in your vehicle in the cooling system. If your tank has experienced damage such as cracking, nipples breaking off, or mounting point damage, you will need to replace it.
All BMW E60/E61 and E63/E64
The coolant expansion tank cap keeps necessary pressure on your coolant to increase efficiency. If you have an overheating issue in your vehicle, a simple, quick, and inexpensive part to replace is this cap. Often times, the coolant is not kept under enough pressure to keep it from boiling or expanding too much. This cap keeps all the heat and liquid inside the coolant system for maximum efficiency. Should be replaced each time major coolant system service is performed.
Fits all BMW vehicles
This is the same Genuine BMW coolant you would buy from the dealership.
Section 1 - BMW Coolant Expansion Tank Replacement
Replacement of the coolant reservoir is exactly the same procedure on both the 5 and 6 series vehicle. The only difference is six cylinder 5 series vehicles have one less coolant hose that needs to be disconnected (see step 5 below).- Make sure engine has completely cooled before starting this repair.
- Identify the location of the BMW coolant expansion tank in your vehicle.
- Position a 5 gallon drain pan under coolant expansion tank to catch any spilled coolant.
- Remove the vent hose by using a metal pick to release the metal clip and pulling free from the expansion tank. If hose will not pull off, use a flat blade screwdriver and the palm of your hand and gently push off.
- If working on an 8 cylinder (N62) model, remove the overflow hose using the same technique as in step 4. Six cylinder models do not have an overflow hose.
- Use a T20 torx bit to remove the two BMW coolant expansion tank mounting screws.
- Pull the coolant expansion tank out of engine compartment until you can access the bottom reservoir hose.
- Remove the reservoir hose using the same technique as in steps 4 and 5 above.
- Remove the fluid level sensor electrical connection on bottom of expansion tank.
- Remove the BMW coolant expansion tank from the vehicle.
- Install new coolant expansion tank using the reverse steps above.
- Fill reservoir with fresh coolant, replace cap, and start engine. Allow coolant to circulate through engine for a couple of minutes. Turn off engine, remove cap, and top off coolant if necessary. Only use Genuine BMW coolant/antifreeze mixed 50/50 with distilled water.
BMW Coolant Expansion Tank Replacement Finished
