Water leak from engine Block

Gentlemen, I have discovered a serious leak from the capsule? on the engine Block on my P6 V-8 and wonder how to solve this. I have no name for the circular capsule (one of three on the right side) but it is clearly seen on the repair operation manual for P6 (page 12.21.46 sheet 3)
question: is it possible to change it without taking to engine out? How can I get hold of such capsule? How do I replace it? What is the purpose of this capsule? Any suggestions? Thanks, Chris Varming 2BE8D50C-2717-4EA9-B43B-CACEF7E86CFA.jpeg


Well-Known Member
Staff member
Hi Chris,

That is a core plug, also called a welch plug, or a freeze plug. They are a protection device for the engine in the event of the coolant freezing. Given the coolant will expand as it freezes, the plugs push out under the expanding coolant to minimise the potential of the block cracking. To remove it, use a cold chisel striking in the centre, then prise the plug out. Apply sealant such as a silastic or permatex around the contact surface of the new plug and drift it in accordingly, making sure it is square as you do. You can source them from any Range Rover business, just ask for a set of core plugs for a Rover V8. Their size didn't change over the years.



Well-Known Member
If one is leaking then the others probably aren't far behind so best if you can to replace them all. Providing you can get access they can be replaced with the engine in-situ, apart from the one on the rear of the block where either the engine or the gearbox will have to come out. Not easy though.


Active Member
The core plug holes are left in the cylinder block during its casting and are there to hold the sand Cores in place during the casting process, otherwise they could "float" about as the aluminium is poured into the mould . The cores form all the internal water ways and such. The sand is then knocked out and the holes are them machined to take the core plugs
I don't know if its the same for alloy blocks, but when I changed the plugs in my iron block Cortina I used brass on the hard to reach ones but mild steel on the easy to reach....because apparently they are also sacrificial to help reduce corrosion in the block itself....or so I was told by a mechanic who was a mechanic before they built the Ark....