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. 

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BMW E61 Hydraulic Liftgate Pump Rebuild

The liftgate hydraulic pump in my 2010 BMW 535xi Touring lost hydraulic fluid level about 2 years following a quick fluid level top off. This time, there were two issues: i) bad seals on the liftgate cylinder; and ii) failure of the seal in the hydraulic pump accumulator piston, leading to leakage below the pump. 

I'll do a writeup on replacement of the lift cylinder separately. This post describes the replacement of seals and o-rings in the pump assembly.

BMW Hydraulic Liftgate Accumulator bore, piston and spring following dissasembly

When your liftgate starts struggling to reach the full open position, troubleshooting is fairly straightforward. The pump is located in the rear compartment, directly below the liftgate cylinder on the left hand side of the car, attached the left rear fender. To access, remove the left hand rear storage compartment door, then remove any audio components hindering access. Be very careful disconnecting the fibre optic connections on the audio components.

BMW Hydraulic Pump - low fluid level, fluid weeping from the accumulator (left side of pump)

Once you can see the pump, you'll note the "+" sign on the side of the plastic fluid reservoir. The oil level should be in the center of the "+" sign. In my case, the fluid reservoir was nearly empty, with traces of hydraulic fluid dripping from the accumulator housing (to the left of the fluid reservoir). 

Unfix the pump, lift to show bottom of accumulator and fluid weeping from vent hole

There are some gymnastics required to unfix the pump. Some can remove the pump without removing the left rear cargo area trim panel. If you're removing the pump for a rebuild, it may be easier to take the time to remove the trim panel. 

Once you have the pump removed from the car, and the hydraulic lines to the cylinder disconnected, you're ready to work on the replacement of seals. In the photo below, working clockwise from 12 o-clock, you have the motor top right. You have the mechanical pump mid right - between the motor and reservoir. The reservoir is bottom right. To the left of the reservoir is a hydraulic accumulator (a piston and spring designed to maintain hydraulic pressure, which holds the liftgate in the open position without the motor / pump running.) Just above the accumulator is a valve body, where the hydraulic lines connect and where the pressure sensor (top left) connects. 

Right side: Motor, pump and reservoir. Left side: Accumulator, valve body, and pressure sensor.

Removing the pressure sensor is straightforward. Remove the two hex head cap screws, and pull the pressure sensor straight up. The pressure sensor is sealed with a single o-ring - 9mm x 2mm. (All o-rings mentioned in this post are described by inside diameter (ID) then thickness. For outside diameter (OD) - double thickness and add to the ID.)

Pressure sensor with cap screws, and o-ring seal at base

I removed the motor, it is sealed to the pump with a single o-ring (41.6 x 2.4mm). I made no attempts to remove any pump components, I removed the pump, tried not to change the indexing of the drive spring, replaced the o-ring and replaced the motor. 

Motor removed. The o-ring stayed in the pump recess, it removed with a pick. 

In order to remove the accumulator piston, you need to split the two halves of the pump assembly. There are two long hex head countersunk screws which hold the two halves together. When you split the two halves, you'll note 5 oil passages which are sealed with small o-rings (4 x 1.5mm). Replacing these o-rings is very simple, just pop out of their recesses and clean any debris with a clean, lint free rag. 

Left and right halves separated - note 5 sealing o-rings.

Once you have the two halves separated, you can disassemble the accumulator. There are four hex head countersunk screws which hold the bottom plate to the accumulator body. Remove them slowly, and remove them equally (a few turns on each screw in rotation) because the bottom plate of the accumulator is under spring pressure. By separating the two halves of the pump, you ensure that the piston is at the top of the bore by removing any hydrostatic pressure remaining under spring tension. 

Accumulator piston removed from bore, note bits of piston seal disintegrating, dirty fluid

The piston will only come out of the bore with the two halves separated. Try to remove the piston square to the bore - to avoid the metal edges of the piston from scoring the aluminum bore. Same when replacing the piston, avoid rocking the piston in the bore, and insert squarely. The piston is a urethane U-cup seal, 35mm ID, 45mm OD, 7mm tall. 

Accumulator disassembled - piston, seal, spring, base and screws

Old accumulator piston seal on the left, new urethane U-cup seal on the right

New seal on the piston, old seal on the right

The final seals which are replaceable are the reservoir to pump seal which is a 39.4 x 3.1mm o-ring, and the reservoir drain/fill port, which is a 6.1 x 1.6mm o-ring. Reassemble in the reverse order of disassembly. Ensure that the accumulator is reassembled before assembling the two pump halves. 

After having rebuilt the pump, and disconnected / reconnected the cylinder hoses, you will need to bleed air out of the system. Reinstall the pump in it's normal location behind the left rear wheel well, but keep the reservoir off the pump. I used some 1/4" vinyl tubing to draw oil from my replacement oil can, and to reject oil and froth from the return line to an empty aluminum can. 

Bleeding the pump using vinyl hose. Note froth returning to the aluminum can. 

I used AeroShell 41 Hydraulic Fluid for this repair

Once the froth turns to a consistent air free oil flow, you can stop bleeding, remove the vinyl hoses, and partially replace the reservoir cup. I then refilled the reservoir using a syringe and vinyl hose to get the fluid level back to the "+" sign on the side of the reservoir. I used a regular stainless steel band clamp to hold the reservoir on the pump. 

Refilling the reservoir with the pump mounted in the car

Reservoir replaced, topped up to the correct level. 

I purchased extra seals when I completed this project, I'll put some seal kits up for sale on eBay for anyone interested in doing this repair.

I've made some repair kits available at this link. 

I've made some hydraulic fluid and refill kits available at this link.

Let me know if you have any questions in the comment section below. 

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BMW 535xi Touring E61 Tailgate Hydraulic Strut Popping off the Ball Joint - Set Screw Repair

My BMW 535xiT is my daily driver - use it for going back and forth to work every day and running all the errands to keep the household running. So - the tailgate and back window get lots of use. The car was manufactured in September, 2009 and now has 175,000 km on the odometer, and since BMW hasn't inported the 5 series touring to North America since 2010 - it looks like I'll be hanging onto this car for a while longer. The 3 series touring is too small, I'm not an SUV kind of guy, and I'm not ready to go to a Mercedes E series wagon just yet...

The completed set screw repair - neat and flush. 

So - about 6 months ago the hydraulic strut in the tailgate stopped lifting all the way to the top of travel - it started sagging and making ominous noises. So - I took the time to dig out the hydraulic pump and reservoir, replace the fluid with the BMW service kit, change the 10mm strut ball and get the tailgate functioning well again. I wrote about all that here.

Well - it took about 3 weeks until the hydraulic strut started popping off the ball - you can see the state of the bottom socket on the hydraulic cylinder here, there was finally enough wear that it wasn't going to stay in place.

This is not good....

This isn't good either....

So - just to keep the socket engaged, I cut a piece of styrofoam to jam in behind the strut to try to keep it in place - that worked fairly well for about a month, then the strut would pop off about every time I opened the tailgate, and it was time to make a more permanent repair.

There was a good discussion on the 5series.net forums, the idea that I decided to try out was a set screw. I did a bit of research and found some really nice ball tipped set screws and decided to try them out. 

5mm ball tipped set screws

So - I ordered a lot of these set screws and set out to do the repair.

To drill and tap a 5mm hole - you need a 5mm tap, and a 4.2mm tap drill bit

First step is to dismount the strut from the tailgate - you need to remove the plastic trim on the left side of the window. There's a small clip you need to get out of the way to get the trim off. 

Lift the trim underneath the window to get this clip out of the side trim.

Removing the lower half of the left hand tailgate trim - once this is removed, you can remove the hydraulic strut. 

With the hydraulic strut removed, it was time to set the hole placement for the set screws, and drill two holes - one on each site. I put a small sheet of plywood on top of the security screen - was very useful to support the strut during the machining.

With the strut removed, it's easy to rotate to drill and tap the set screw holes. The plywood makes a good work surface.

I aimed the drilling to intersect close to the steel circlip. Very important to use a pilot drill to locate the holes properly - a pilot hole of 2.5mm would be perfect before drilling out to 4.2mm which is the tap drill size for a 5mm tap. 

Drilling each side of the strut base. 

The first hole on the top side - this hole walked a bit because I didn't use a pilot drill hole - don't make the same mistake I did...

Aim for the steel ring clip...

With the first hole tapped to 5mm - testing out the set screw. 

With the holes drilled out to 4.2mm tap drill size, it was very easy to tap the holes - this is a fairly soft steel part and it cuts well. 

Strut replaced, and the set screw does a great job holding the strut in place. The bottom set screw is easily accessible.

To access the set screw on the top side - its easiest to access with the window open and the left side trim off.

A dab of blue Loctite will hold the set screw in place, keep it from backing out. 

In case anyone is interested, I've created an eBay listing to sell the surplus set screws from the lot that I had to purchase - you can purchase the set screws here at eBay listing 183298383219.

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BMW E61 5 Series Wagon Hydraulic Tailgate Lift Repair

Today I spent about 5 hours repairing my hydraulic tailgate actuator. There lots of discussion about this issue on the forums, I thought I would add some photos from my experience to help those considering or performing this repair.

Correct oil level should lie within the "X"
You can see the oil level is quite low - about 25mm below 

What was wrong? The hydraulic system sounded like it was straining to lift the tailgate. Did not sound normal. The tailgate wasn't lifting up all the way - was settling back down about 10cm lower than normal. And - the hydraulic actuator on the right side of the tailgate started popping off the ball joint - when that happenned, the lift would not operate normally and had to be reset by hand.

So - did some research, and then ordered the following parts:

1. Pressurized gas cylinder for the right hand side of the tailgate.
2. A pair of new 10mm ball joints
3. The hydraulic repair kit from BMW - which includes some hydraulic fluid and a bunch of small parts.

Then - I got started.

If you are going to top up the hydraulic fluid - start by opening the tailgate, closing the tailgate, then opening the tailgate again. This bleeds the system.

Start by supporting the tailgate with something solid - like a painting pole

I started by switching out the right side gas pressurized strut. I removed the old one - it just pops off the ball joints with a bit of gentle force.

E61 Gas Pressurized Struts - New on the Right, Old on the Left

I then took a bathroom scale and measured the force of each strut compressed about half way. The old strut had a force of 96 pounds half compressed. The new strut has a force of 138 pounds half compressed - a little over 40 pounds different. This may explain part of the reason why the hydraulic system sounded like it was straining. Replacement struts are not that expensive, even from the dealer. The new OEM strut even comes with a dab of grease inside the ball joint so that it is ready to install. Check yours - make sure it is greased to protect the ball joint from wear during opening and closing.

Old vs. new ball joint for right hand side gas pressurized strut.
Not bad condition overall. 10mm diameter ball.

With the gas strut changed - I then turned my attention to the left hand hydraulic side. I began by popping off the hydraulic actuator and trying to replace the ball joint.

Left hand ball joint - rusted and frozen in place

It was jammed, and I stripped the hexagon faces trying to remove it dry. So then I soaked it with penetrating fluid, and got onto it with a pair of vice grips.

Penetrating fluid helped a lot. Vice grips tore up the ball joint, but it ended up finally coming out. 

So - I decided to top up the hydraulic fluid while allowing the ball joint to soak in penetrating fluid. Every 10 minutes or so over 3 hours I added another squirt of penetrating fluid. On to the hydraulic system.

Hydraulic pump is just underneath the left rear access panel. The radio module is Sirius satellite Radio. 

Start by removing the left rear access cover - it just unclips and comes off. Next, remove the radio module if you have one - 4 screws hold the radio module to the bracket, then 4 screws hold the bracket to the car. I didn't bother removing the radio wiring harness, I just let it hand from the back of the car during the repair.

Hydraulic pump exposed - correct oil level runs through the X - you can see the level is quite low.

There are 2 nuts holding the bottom of the hydraulic pump bracket, this comes out with a 10mm socket. The upper part of the bracket is held by an 8mm hex head screw - comes out well with a 1/4" drive socket and short extension. 

Upper bolt removes with 8mm socket, short extension. 

By the way - make sure you have a nice 1/4" drive socket with a fairly light mechanism - you'll thank youself. The folding handle is really convenient in these tight spots.

Once the bracket is undone - you go underneath the bracket and remove 3 nuts holding the pump to the bracket - 6mm. 

Once the pump is freed from the bracket - reach up to the top and free the hydraulic lines from a small clip, and free the electrical harness from a zip tie clipped to the bracket. Once these are free - the pump is free to descend. You'll also need to remove the electrical connections - one plastic connector, and two individual wires that connect to the motor underneath a black plastic circular cover over the motor. 

Motor power connections under the black plastic cover. 

Then you can continue following the BMW instructions. I drained all the oil from the reservoir into a small pan.

Draining the oil from the reservoir. 

The drain plug is a small metal plug in the very bottom of the plastic reservoir. You don't need to (or should not) remove any of the hydraulic plugs from the pump. Then you can refill the reservoir. If you purchased the BMW kit - you'll have a new drain plug complete with O-Ring to reseal the reservoir.

Installation is the reverse of removal. Redoing the electrical connections is a bit tricky. Once the electrical connections are replaced - test the tailgate before bolting everything in. It might saving you having to remove the pump a second time to check the motor connections (from my experience...).  

BMW repair kit contents. The bottle of oil has a nipple the same size as the drain fitting on the reservoir - very nice. 

Then I went back to removing the left side ball joint. Three hours of penetrating fluid loosened it up - it was still very difficult to remove.

Chewed up the old ball joint removing it with vice grips. New 10mm ball joint on the right. 

Use lots of anti-seize on the new ball joint - might save the next owner of the car a lot of trouble. 

Socket at the end of the hydraulic actuator needs cleanup. 

So - I cleaned up the socket end of the actuator - toothbrush and penetrating fluid to get all the rust and crud out of the socket. Then I blew it dry with a bit of canned air, and filled it with waterproof grease. I popped the socket back on the new ball and it held.

Cleaning out the socket. 

Completed repair. I put a small section of stiff rubber fuel line next to the actuator, just to give it a bit of support to help it keep from popping off again. I'll update the post if this works. 

So - about 5 hours to do this repair from start to finish. The topped up hydraulic system works nice and smooth - like new - no sound of straining. The tailgate now closes and locks with a firm click. All good. 

The culprit - worn ball joint - chewed up by removal with vice grips. 

Update - 2 Years Following the Fluid Top Up

I use the car daily, use the glass window typically daily, and the liftgate hydraulics multiple times a week, several times an outing. So - the liftgate sees regular service. After about two years - my hydraulic strut developed a leak at the rod seal, and eventually the oil loss was enough to prevent the liftgate from going to full extension. I just recently replaced the hydraulic strut, and rebuilt the pump. I've completed a new post on the pump rebuild at this link. I'll do a new post on the cylinder replacement as soon as possible.

Sources and Links

The replacement 10mm ball and fluid kit was sourced from my local BMW dealer - Park Avenue BMW in Brossard. Total cost was in the order of $200.

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