What kind of urethane caulk do I use?

Does your Highlander have a sun roof? If so there's more issues than a luggage rack leaking. You likely have plugged up drain tubes in the roof, along with a faulty gasket on the sun roof. The fix is quite labor intensive, and the Highlander isn't the only Toyota with this issue, and it goes back for over a decade. You can search YouTube for videos about the issue, and the repair. This is if you have a sun roof.

I’ve used construction grade Geocel on gutters on the house… it’s the best sealant/caulk I’ve used for that application.

I looked and they make one for autos…. Maybe try to find this



ETA: just visited highpockets’ link… also geocel Looks like a good one too

Thanks!