Overview
Every hole drilled through the vehicle floor for exhaust, intake or wiring is a potential exhaust leak and water entry point. This guide explains how to seal penetrations correctly.
Hole Sizes
Exhaust pipe: 35 to 40 mm hole. Combustion air intake: 35 mm. Wiring: 20 to 25 mm. Use a hole saw with a pilot bit. Deburr the edge.
Grommets
Use rubber grommets sized to the hole. The grommet protects the exhaust pipe from chafing on sharp metal. For hot exhaust, use a high-temperature silicone grommet, not ordinary rubber.
Sealant
After routing pipes, seal around the grommet with heat-resistant silicone. This prevents exhaust fumes from entering the cabin. Test with a smoke pencil after installation.
Water Entry
Seal the top and bottom of the penetration. On the underside, use a marine-grade sealant. On the inside, use foam or trim ring.
Wiring Holes
Use a rubber wiring gland. Leave a drip loop so water runs away from the cabin. Seal around the cable.
References
[1] European Union Regulation (EU) 2015/1188 on monitoring and reporting of CO2 emissions.
[2] European Union Regulation (EU) 2015/1186 on type-approval requirements for motor vehicles and engines regarding emissions.
[3] SAE International J1455: Recommended Environmental Practices for Electronic Equipment Design in Heavy-Duty Vehicle Applications.
[4] FCC Part 15 Subpart C: Intentional Radiators.
[5] ISO 6722: Road vehicles – 60 V and 600 V single-core cables.
[6] U.S. EPA Idling Reduction Fact Sheet for Heavy-Duty Diesel Vehicles.
[7] ISO 8820-2: Road vehicles – Time-lapse current-limiting fuses.
