The bolt, on the passenger side, holding the third brake light broke and it is no longer water proof. I saw it pooping up on the one side months ago but did not realize it would start leaking. I found out after running the car through a car wash a couple of weeks ago and seeing water drip from the top of the rear window.
I really didn’t want to work on this in this heat but I couldn’t find anyone to do it for less than $350.
I ordered the light from GM parts ($60) but the nuts didn’t come with it so I picked up some 8mm Keep nuts from the local Ace. It took half the day to make enough room in the garage to get the car in.
I had to tap out two of the bolts but it only took about an hour to complete the job.
I have to say, I think this is a really poor design. The bolts are embedded in the underside of the plastic fixture. Two had popped out before I even started this repair and one when I tried to take the nut off from inside. I didn’t have to tap this one though. A pair of vice grips, some gentle persuasion on the first few threads and I was able to spin that nut off rather quicklyremove that mount, Only one of the four mounting bolts came out as it was supposed to.
While researching the problem I read that the nuts needed to be torqued to no more than 8 N⋅m (Newton-metre). I had to buy a new torque wrench. I didn’t have one that would go that low accurately. I found this one, free delivery in 5 days:
https://www.walmart.com/ip/EPAuto-1-4-Inch-Drive-Click-Torque-Wrench-20-200-in-lb-2-26-22-6-Nm/959127170
It turns out that the light fixture I just replaced was also a replaced a few years due to a recall. Unfortunately it also turns out that when the recall was done they didn’t use a torque wrench for the repair so most of those recall repairs failed as well.
I better not have to have to do this again.