BMW E61 Tailgate Hydraulic Lift Cylinder Replacement - 5 Series Touring

About 2 years ago, I refilled my tailgate lift pump hydraulic reservoir, it had gotten low, and the tailgate no longer opened fully. I wrote a post at the time about replacing the ball joints and refilling the hydraulic pump. This re-occurred recently, except this time the fluid was escaping from the hydraulic cylinder, and not the pump. The seals on the lift cylinder are not replaceable, the cylinder is not rebuildable. The end caps are crimped to the cylinder. 

BMW E61 Tailgate Lift Cylinder - Note the weeping seal, and the crimps in the cylinder wall.

So - what to do? I managed to find a decent looking cylinder complete with hydraulic lines and pump on eBay, from a European vehicle. Canadian winters and cold weather are hard on components like these, hopefully the part I purchased has had an easier life and will serve me for the rest of the life of the car...

Note the oil crud buildup in the well under the cylinder - the cylinder was losing lots of fluid.

So - with the replacement part in hand, it was time to get at the repair. First step is to get access to all the hydraulic lines. You'll need to do the following preparation:

• Remove the left rear D pillar trim which encloses the cargo cover mechanism
• Lower the headliner 
• Remove the left side cargo trim - both the access door and the wheelwell cover

Starting with the D pillar trim, it is fairly straightforward. Start by removing the tailgate weatherstrip. With that removed, there are two screws which hold the cargo cover mechanism to the inside of the D pillar trim - at top and bottom. At the bottom, the screw is exposed and easy to find. At the top, there is a rubber bumper which limits the top of travel for the cargo cover, under this bumper is the second screw. 

Removing the D Pillar trim, note the body clips (top and bottom) and cargo cover mechanism

Top screw retaining the cargo cover mechanism (inside of D pillar trim)

Note the rubber bumper - remove this to access the top screw

Bottom fastener exposed next to cargo cover mechanism

With the D pillar removed, you can now drop the headliner. To do this, you'll need to remove the two rear roof speakers, and also remove the clip for the cargo screen / roof attachment. You shouldn't have to remove the C pillar trim, nor the D pillar on the other side. 

There is a screw inside the cover which allows you to remove this clip

Removing the left side cargo wheel well cover is a bit tricky - you need to remove the left side passenger seat bolster, lower the seat, and then remove the plastic cover underneath the quarter window, just behind the C pillar. There doesn't seem to be an elegant way to do this - I just ended up forcing it with a trim tool and it eventually popped out with one of the plastic tabs broken. With this part removed, you have access to all the fasteners along the top of the wheel well cover. Everything else is fairly straightforward. 

Removing trim cover behind C pillar

With the side panel removed, you'll need to access the hydraulic pump and it's connections. You may need to remove a radio module to gain access - be very gentle with the purple fibre optic connections - if you break one of these, you may be looking at a trip to the dealer and a lot more hassle. 

Remove the hydraulic lines to the pump. Just remove the two wire clips, and the hydraulic lines will pull straight up. Take care when removing and inserting these connections, to my knowledge, the seals inside the connectors are not replaceable. 

Connections to the hydraulic pump are foolproof - Red to Red, Blue to Blue. 

This is a good opportunity to inspect the pump and see if it is leaking fluid from the accumulator. You may notice a puddle of fluid underneath the pump, if it's bad, it will run down underneath the cargo floor towards the spare tire well. This is a good time to remove the pump and replace the accumulator piston seal - check out my post on resealing your hydraulic pump here. 

With the hydraulic lines disconnected from the pump, you'll need to disconnect the limit switch electrical connector which is directly above the left rear speaker. This will avoid damage to the harness when you're removing the cylinder and lines. 

Lift cylinder limit switch electricla connector above left rear speaker

The hydraulic lines curve around 180 degrees clipped to the roof, just left of the left rear corner of the sunroof. With the headliner dropped, you'll need to access the clips and detach the hydraulic lines. Take a few photos and note the routing of the hydraulic lines with respect to the electrical harnesses and sunroof drain.

Disconnect hydraulic lines from two clamps holding lines to steel roof

This is an excellent time to verify your sunroof drains are not blocked, just pull the drain off the sunroof frame, and blow through some air to ensure it's clear. 

Sunroof drain hose, and connection at back of sunroof frame

With the two hydraulic lines disconnected, the electrical limit switch connector disconnected, and the clips removed holding the hydraulic lines to the roof, you can now pull everything through and remove from the car, from the exterior. 

Removing the cylinder and hydraulic lines. 

Installation of the replacement cylinder and hydraulic lines is essentially the same process in reverse. 

To assist with pulling the hydraulic lines through the roof to the opening left of the sunroof, I used a piece of stiff cable as a pull cable (old piece of TV coax cable). And - to assist with pulling through the electrical cable to the left rear speaker opening, I used a piece of twine. 

Prep for reinstallation - cable for pulling hydraulic lines, twine to pull electrical cable

Hydraulic lines pulled into the car, just need to pull through the electrical cable

To finalize the installation:

• Reroute the hydraulic lines, and clip them to the roof. 
• Do not forget to reconnect the sunroof drain
• Reconnect the limit switch connector under the left rear speaker
• Reinstall the cylinder to the ball joints - ensure they are properly lubricated for long life.
• If you've removed your pump and replaced the seals - reinstall the pump. 
• Reconnect the hydraulic lines to the pump - red to red, blue to blue.

There will be a lot of air in the hydraulic lines now - the best thing to do is to bleed the system following the procedures mentioned in my post on rebuilding the hydraulic pump here. 

If you haven't already done so, you may wish to replace the right side pressurized gas strut, this will help with lifting the tailgate and reduce the work done by the hydraulic system. 

Prior to reinstalling all the trim, this would be a good time to test and sure everything is functioning normally. 

Then replace the trim and the headliner.

Let me know if you have any questions or comments below.