Thread: LR072856 High Mounted 3rd Brake Light - what sealant/silicone adhesive to use?

Originally Posted by twr7cx

What sealant or silicone adhesive is used when replacing the LR072856 High Mounted 3rd Brake Light? I assume something like Sikaflex 227 would be detrimental to the next time the light housing needs to be replaced.

Sikaflex was a complete failure when I saw my new HM Light spiralling through the air in my rearview mirror and it was professionally fitted. The windscreen shop covered the cost of a new replacement but refused to fit it. I did it myself using clear gutter silicone after a test on the broken one and it has held firm for two years so far. Nick

I used sikaflex and copious amounts of it, plus prepared the surfaces really well including alcohol wipe down etc. mine has never leaked or come off. I think in the above case it wasn’t the adhesive’s fault but the person who applied it ineffectively. If you follow the instructions and look how much the factory uses, it’s a lot.

Originally Posted by DiscoJeffster

I used sikaflex and copious amounts of it, plus prepared the surfaces really well including alcohol wipe down etc. mine has never leaked or come off. I think in the above case it wasn’t the adhesive’s fault but the person who applied it ineffectively. If you follow the instructions and look how much the factory uses, it’s a lot.

The person that applied it did use an activator before fitting with Sikaflex but the bond was very week. If you are fitting one yourself it's wise to do a test on the old one first just to be sure.

Forget 227. Sikaflex 296 is the professional marine glass bond. If that doesn't stick, there's something wrong with your process. It's rated as suitable by the international maritime organisation... That's an approval for where people might die if it fails... (I build wooden boats as my other passion). 3M also do some outstanding adhesives with a bit of flex/temp 'give' in them, but not sure which one would be right for glass/acrylic. The one that is used on wood is affectionately known as 'the devil's toothpaste' - once it's cured, most boatbuilders accept that the bond is unbreakable if you want the substrate to survive...literally - you cut it out and start again.

I'm interested to know how you go/went getting the old one out? Heat it up first or just smash and scrape away?

Originally Posted by Stuart02

I'm interested to know how you go/went getting the old one out? Heat it up first or just smash and scrape away?

Complete demolition and then knife out the old adhesive with a scalpel

Yeah that’s how I did it

I'm not sure I'm brave enough!