Sealing Roof Lights

I'll stand corrected - I havn't been the biggest fan of butylmastic due to the crust it forms and tends to dry out and shrink a bit. And I disagree with the comment that Sikaflex causes rust as it is not acidic. Holdens rust without help from a third party (like Bedfords)

However, majority rules and eventhough I spent a lot of years in the motor trade it wasn't fitting windscreens so I'll concede and back Rookie on his advice

And I disagree with the comment that Sikaflex causes rust as it is not acidic. Holdens rust without help from a third party (like Bedfords)

Oh, I didn't mean to infer than sikaflex causes rust, :-[just meant that if theres bare metal under the sikaflex when its applied, its not going to stop the rust from happening if moisture is present. And it will not stick to rust. Acidic silicon is a no no as has already been said. I reacon the award for worst rust around the screen would have to go to Mitsubishi.

My two cents worth and sorry if I stir the possum.
I used soft nitrol rubber sheet and cut out some new gaskets on the 190 and fitted em with no goo and its fine. Spent a fair bit of time shaping the light bases to fit the roof profile also. Threw the crappy hard plastic gaskets away they supplied with the lights.
Like wise my horn base was flat but the roof has a gentle curve in the mounting area. With a softer rubber gasket it can take up the differance and you wont get a smile in your gasket. It doesnt leak either.
If your light bases dont have the same profile as your roof you will struggle to get them to seal with goo. You will for a few months but it will detach itself somewhere and water will get in. Try shapeing the base of the lights so they fit the roof profile perfect and use a good quality rubber gasket and see how you go.
Take the lights of a new truck cab....any goo there, I doubt it. They fit properly.

Basil