The valve covers on the Mitsubishi Montero are made of pressed steel or aluminum, depending on the year and engine size. Both types of valve covers use rubber gaskets. If the gaskets become dry-rotted or otherwise cracked, oil leaks out onto the sides of the engine. The valve cover gasket for this vehicle comes with spark plug tube seals, if the engine is of the type with the spark plugs through the center of the valve cover.
Disconnect the breather hoses that run to the valve cover at the cover. Label the spark plug wires, using the tape and marker, then pull the wires off the plugs. Depending on the engine, the valve cover might overlap the timing cover or the timing cover might overlap the valve cover. If the timing cover overlaps the valve cover, remove the upper timing cover, using the appropriate socket. Remove the valve cover using the appropriate socket.
Lift the valve cover off the head. If it is stuck, tap it gently with the rubber mallet. Remove the half-circle seal at the end of the valve cover -- if it's not on the valve cover, it is stuck on the head.
Clean the gasket-mating surfaces on the valve cover and the head, using a brush or rags, and if needed, carburetor cleaner. Coat the gasket-mounting surfaces on the valve cover with a 1 mm bead of RTV silicone. Install the half-circle plug and the valve cover gasket on the valve cover, ensuring that both stick to the RTV silicone. Place a 10 mm dot of RTV silicone on the each side of the seal on the head surface. Allow the RTV to skin over. When you touch it, it should not stick to your fingers -- this takes from two to ten minutes.
Install the valve cover. Install the bushings through the valve cover. Tighten the retaining bolts evenly to 38 inch-pounds of torque by setting the torque wrench to 38 inch-pounds, then tightening each bolt two turns at a time until the proper torque is reached.
Reinstall the timing cover, plug wires and the breather hoses. Allow the vehicle to sit for 90 minutes before starting it, to give the sealant time to cure.
