Monty tapping at start up.

Usually it's a sticky valve adjuster (Hydraulic) in a Mitsubishi if the sound is coming from the top end of the engine. Can't see a temp sensor causing any noise.

Sometimes, you can get them to bleed out and quiet down, but often you need to replace them. Often a "discount" rebuilder will reuse them. If the noise never goes away, if you can isolate the bank of the engine with the noise, you can pull the valve cover and inspect for a worn cam lobe.

Mitchell time to remove the rocker shafts is 3.1 hours labor on the left bank, 2 hours on the right bank. Rocker arms hold the tensioners.

Mitsubishi Technical Service Bulletin # 99-11-006 shows how to clean them with diesel fuel. They need to be removed for cleaning.

TSB 91-11-009 and TSB 95-011 explain how to try to bleed them while they are still in the engine.

TSB 97-11-002 gives diagnosis info

No, the hydraulic adjusters just take up the slack in the valve train, they slip into the valve end of the rocker arms. They slip into the rocker arm hole seen in the picture.

Thanks man. Its coming along. Wire wont let me load pics unless resized.