Water Leaks into Tacoma Cabins Through 3rd Brake Light

Water can leak into the cabin of a 2016-2018 Tacoma because Toyota did a terrible job sealing the 3rd brake light mounted above the bed. There's a gap between the LED light and the body that collects water. Meanwhile, a cheap brittle gasket does little to stop that water from leaking into the truck.

The problem only affects double cab versions of the truck, as the access cab uses a different light assembly.

Water Leaks Always Cause a Lot of Damage ∞

Even a small amount of water can do significant damage. If an owner doesn't spot the leak right away or the water drips behind trim panels, there's concern about mildew forming or electrical wiring fizzling out.

As the leak worsens, it stains the headliner and can pool on the back seats.

An overly complicated and costly repair ∞

The "high mount stop lamp" is mounted from inside the truck which means to service or replace it, you need to remove the b-pillars and drop the headliner. That's a heck of a lot of work just to access two 10mm screws holding the darn thing in place.

Covered under the standard warranty ∞

The work to replace the light is only covered under the standard 3 year / 36,000 mile warranty. In July 2018, Toyota released service bulletin #0055-18 titled Water Leak at Rear of Cab -Center High Mount Stop Lamp that outlines the steps needed to confirm and fix the problem.

The service bulletin only applies to specific VIN ranges of the 2016-2018 Tacoma double cab.

For everyone else it's at least $500 ∞

Once you're out-of-warranty the light is deceptively expensive unless you want to replace it yourself. On average the cost of repair is around $500, mostly for labor, as the part MSRPs for around $150.

The good news is while the original OEM part (#81570-04040) seems to just be held on with double-sided tape and the faintest hint of a foam gasket, the newer version from Toyota (#81570-04051) comes with a much thicker gasket.

As shown by a post in the Tacoma World forum:

it’s a thicker foam gasket. Original looks like it was just thick double-sided tape. Barely holding on up top, leaking in two places.

Other repair options ∞

Some say if they're going to go through the trouble of dropping the headliner they'll just replace the whole assembly with a fancier 3rd party option. While others try to DIY it with a bead of clear silicone sealant around the outside of the light, hoping that'll stop the leaks.