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.