Alpina D3 E90 boot struts

The component has a cylindrical housing. A piston with a rod is mounted inside. It divides the housing into two chambers. The part is filled with nitrogen. When the boot lid or the rear door are closed, the gas under the piston is compressed. When opening the boot, the gas starts pushing the rod out of the cylinder.

In pneumohydraulic springs, the oil contained in the bottom part of the cylinder is responsible for stopping the piston. The speed of its movement is reduced rapidly, as damping is performed only at the end of the piston travel. Usually, such components are installed with the rod downwards.

Gas springs have special grooves in the walls of their cylinders: the gas passes through them into the second chamber to create backpressure which gradually increases. This makes the lid open smoother. This kind of parts can be mounted both rod up and rod down.

The product is nonrepairable, it can only be replaced as an assembly. Note that it’s dangerous to disassemble it, as it is filled with highly compressed gas. Failure of these components is often indicated by:

• oil stains on the housing;
• corrosion marks;
• performance loss.

These parts should be replaced in pairs, as they have the same working lifespan. It is advisable to inspect them and lubricate their fasteners regularly: by doing so you can extend their lifespan.

Depending on your car model and make, the steps may vary. Usually, they are as follows:

1. Using supports, secure the boot lid open.
2. If necessary, remove the boot trim to access the fasteners. Depending on their type, you may need a ring spanner of an appropriate size or a flat screwdriver to undo them.
3. Remove the strut.
4. A new part should be primed in the following manner: press its rod inside the cylinder until it stops, wait for a few seconds and release it to let it return to its initial position. Repeat it about 10 times.
5. Install the new part.
6. Check its functionality.