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      01-10-2013, 03:13 PM   #1
Alonne Captain
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Drives: '17 M240i
Join Date: Jan 2013
Location: Central, New Jersey

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Diy Replace Third Brake Light

Hey guys,

I've noticed that no one has actually replaced the 3rd brake light themselves. Well went ahead and did it. This is my 1st brake light that i am replacing since owning the vehicle. I just bought an 2008 135i and noticed it was cracked about 2 days later (probably cracked when i biggie). I've been searching for a while on here to find out a how to but could not find one. All of my images will be in thumbnails which hopefully all can view. If not please pm me and let me know that there are issues with the images. Okay so without further adieu here it is:

The first thing i did was i shopped around to find a good price. The dealership near me (Flemington, NJ) has the third brake light priced at 75.00. I found an OEM one on ecstuning and paid 65.00 to have it shipped. is the 10.00 difference worth it? We'll see in a couple months. The box that the brake light came in is straight from the factory.

So to start officially, there are several plastic rivets holding the liner in place on the trunk lid. Remove them very carefully so they do not break. I recommend using something plastic as a screw driver might break them. I unfortunately had to use a screw driver (flat tip) but did it very easily so they didn't break, all mine are still intact. Once they are all down, you'll notice that the trunk eject pulley will be holding the liner up causing a lot of tension on the line, to alleviate this i used painters tape and taped it to the edge (i did not take a picture of this sorry). There are 4 nuts holding the light in place that are also attached with springs. The nut is 8mm and i recommend having a deep socket 8mm as the screws are very long and a regular size one just won't fit it. (BE SURE NOT TO LOSE ANYTHING!!! I almost lost one of the nuts but saved it.) Using both hands i pressed up on the two screws on the light in the middle. It took a little bit of time to get this out but it does come out. Once out disconnect the cable that attaches to the light. When i pulled my light out a lot of the gasket was stuck to the trunk, i used acetone to clean it off and my finger nail to scrape the remainder. This works well but time consuming. With that done, i moved on to install the new one. Right in the middle of the opening of the 3rd brake light there is a small lip. Upon further examination, the factory light that was installed had been cut there to allow it to fit, mine however was not. FML. I used a dremel and carefully cut out the edges that were on the new one and matched it step by step with the factory one. (there is an image of the two side by side to see the cut).

Installing the new one was definitely way harder. This is when i almost lost my nut. Connect the wire and then line up the holes. It will take a little bit of pushing but once its in you'll be able to tell. I read on other forums that the spring might be causing the issue with why it cracks. I added an extra washer to help in my installation and to see if the extra washer makes a difference. Using the deep 8mm socket place the nut inside of it while holding the spring in place on the screw area. (I didnt have a deep socket so i was pretty screwed when it came to this part. GET THE DEEP 8MM SOCKET IT IS WORTH IT.) I worked from outside to inside when putting the nuts on. I started with the side that had the trunk release because it was a harder spot to get into because you do not want to put to much extra tension on the cable. Then i put on the other outside corner, followed by the two in the middle and voila. You're all set. No brake light out signs in my dash either.

Hope this helps anyone looking to replace it themselves.
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