300tdi rubber plug in block

[bcj]

After doing some work on my defender I've noticed a small rubber plug on block ,kinda below #2 injector -on step in block to the rear of eng. #, bit bigger than 1/4" has fallen apart leaving a hole about 1 1/4"deep to catch muck in.There appears to be another plug to the rear of this as well.
What is this for & should I replace it ?
Where can I source one from?

Brett
110 300tdi c/chassis
109 h/top

[Bush65]

After doing some work on my defender I've noticed a small rubber plug on block ,kinda below #2 injector -on step in block to the rear of eng. #, bit bigger than 1/4" has fallen apart leaving a hole about 1 1/4"deep to catch muck in.There appears to be another plug to the rear of this as well.
What is this for & should I replace it ?
Where can I source one from?

Brett
110 300tdi c/chassis
109 h/top
The oilways for the the camshaft bearings are drilled from the outside, diagonally across the bores where the bearings go and continue down to the oil gallery below the camshaft. When the bearing shells are fitted, they seal off the outer section of the drilled hole (above the camshaft). The shells are drilled on one side to match the lower section of the oilway to allow oil flow from the gallery.

The rubber plugs as far as I can determine are just to plug the hole to keep water and dirt out - they don't seal oil pressure. I just use silicone sealant to do the same.

Edit: You will probably find 3 of these, below #2, #3, and #4 injectors.

[bcj]

Thanks John thought it might be something like that just wanted to make sure
Brett