Butyl rubber, a bit of old inner tube, silicon RTV. Noel.

As Noel says silicone rtv just spread a film in the lid, leave to cure and use the plus is its difficult to lose!

If you use silicone rubber; as long as the cover cannot touch the live terminals, there is no need to let the bead cure.

Tightening against a cured bead will eventually lead to torque relaxation, loss of clamp load, and the risk of coolant finding its way into the terminal box. Which is exactly what we want to prevent!

Just run a small CONTINUOUS bead about 1.5 -2 mm dia, around the edge of the box, or lid, and tighten the screws.

Excess sealant will squeeze out and inwards, sealing any gaps in an otherwise metal to metal joint, without any fear of torque relaxation.

Howard

Cork based materials were commonly used on motor terminal boxes but oil resistant synthetic rubbers are often used now.

Mike