Whats this?

[ModelMakerMan]

This plastic bung in the side of the engine is leaking oil, I tried to remove it to see what it did but I couldnt get it out and didnt want to risk breaking it. Any ideas what its for and why it might be leaking? Ive spadged a load of RTV sealant round it for now so hopefully it will stop leaking. There is a bolt holding it in too.

 

[Roger Fairclough]

Hi Dave.

It's probably for a sensor of some description for another model.

From memory, it's made of plastic and behind the cam lobe outer part is a cylindrical section with a groove for an "O" ring.

When mine started to leak, I made a new plug from a piece of aluminium rod. I machined the rod to make it a push fit into the block. Then cut the rod into two pieces approx. 10mm long. Drill and tap one and drill the other to allow for the bolt that screws into the tapped section. Chamfer the edges where the two meet. Put a suitable "O" ring between the two, push assembly into the hole and tighten the bolt. As the two parts are pulled together, the "O" ring is squeezed out, sealing the hole. You can use a stud and nut if you so wish. Use RTV on the bolt thread or locktite on the stud.

Roger