M3 Loose Trunk Spoiler Reattachment Advice

[jnjaaberg]

I can use some advice on keeping my spoiler attached to the trunk lid of my M3. One side has come loose (the other is still attached). It has come loose because one of the inset nuts has come out and it, along with the second inset nut, have stripped threads. Other than this, the spoiler is in excellent condition.

I rethreded the inset nut that came out and then used epoxy to set it back in into the trunk lid. I also drilled two more holes and added two screws and epoxied the holes they were in. This held for a few weeks until opening the trunk today. The nut came back out of its hole and the added screws came loose. The composite material that the spoiler is made out of isn't strong enough to handle the threads of the screws without breaking loose. Here is a photo of the bottom of the spoiler where it attaches to the trunk lid:

IMG_1108A.jpg

To fix the problem I'm:

1. Considering putting down some adhesive or double stick tape on the base of the trunk lid where it attaches to the trunk, but I'm not sure that it will hold if the spoiler isn't mechancially fastened somehow or

2) I've thought about trying to tap the two holes I drilled in the spoiler that I previously put the screws in and then insert helicoils along with some epoxy and then use screws from there, but I'm not sure that will hold much better than the screws themselves that I tried earlier.

I'm open to any and all advice.

Jeff

[M3AN]

Do 1+2.

#1 will prevent the mechanical fasteners working loose and #2 will prevent the adhesive from stretching off.

That's how it comes from the factory, doing one without the other will almost certainly fail.

[jnjaaberg]

Right now that's where I think I'll wind up--using both the mechanical attachment and the adhesive, hoping the combo will keep the spoiler attached.

I've been debating adhesives and am deciding between 3M trim adhesive and 3M super weatherstrip adhesive. If I go with tape, I'm looking at 3M super strength molding tape. I need to do a little more research to find out which would provide the best bond. If anyone has done something like this with one of these adhesives, I'd love to hear about your experience.

[shogun]

Moved to E36 M3 forum from E36 forum

[jnjaaberg]

I went with the mechanical attachment along with the 3M trim adhesive tape for the fix. To mechanically fasten it, I drilled and tapped holes in the spoiler. The first section of spoiler that you drill through is a rubber piece that is designed to sit as a cushion beween the spoiler and the trunk; its about a 1/4 deep. Then there is the plastic material of the spoiler. After that there is a section of metal frame that I assume the plastic material is formed around. Be careful when drilling as you will eventually get through the metal and into a hollow section which ultimaetly will lead to the top portion of the spoiler. Be sure to take care to pull back the drill in time to avoid going through the top of the spoiler! Tapping this metal gave good bite and the tape is quite strong. I also added some locktite to the screw threads for added security. For good measure I added some of the 3m tape on the side that hadn't yet pulled loose to keep that side in place. After doing some pull testing on the spoiler, I'm certain there won't any further issues with it coming loose.

[M3AN]

Nice result.

[bmwstephen]

what sort of epoxy did you use for it to come loose again?

Did you try to re-install a slightly oversized insert?

[jnjaaberg]

For the epoxy that failed, I used some JB Weld ClearWeld epoxy. I think because it gets hard and doesn't flex may be what caused it to fail.

I tried using a helicoil insert where the original nuts were, but despite numerous attempts at inserting the threaded insterts, they wouldn't go in. I'd tap and retap, but i couldn't get them to seat far enough in withou the tab on the insert breaking off. When I did the tapping and using bolts directly into the tapped locations I didn't have any issues.