I was thinking yesterday that the P38 has been pretty reliable recently and it has now decided to reward me with a coolant leak. Not just a normal coolant leak from a hose, it's coming from the around the bottom 3rd head stud on the passenger side bank.

The engine was fully rebuilt a few years ago with top hat liners, ARP head studs, new gaskets etc. As far as I know there's no coolant passages from the block to the head in the middle so it must mean I've got a cracked block or a cracked head? I can't seem to find much evidence of Rover V8s with cracked heads. I've seen cracked blocks before but I thought generally they cracked behind the liner which lets coolant into the cylinder rather than between the block face/head gasket.

Has anyone seen anything similar?

I've heard of this before. With standard liners the head gasket fire ring is on the top of the block so the pressure on the gasket is uniform over the full surface. With top hats the fire ring is sitting on the top of the liners so if the liner is even very slightly proud of the block surface, there'll be less pressure on the rest of the gasket. The difference in thermal expansion between the steel liner and the alloy block may also have an affect. I would suspect the coolant is getting out of one on the passages at the front and rear of the head, finding it's way between the gasket and block face until it finds somewhere it can escape to the outside world.

Whether or not it needs it I don't know but I always put a smear of blue hylomar on both sides of the gasket around the waterways, can't do any harm and may stop what has happened with you. What sort of mileage has it done since the rebuild? I suspect all it needs is the head(s) whipping off and new gaskets.

I would guess it's done about 40-50,000 miles since the rebuild. As long as it's not the block I'll be happy. I'm thinking of getting some ported heads from v8developments so I'm not concerned about the heads. I think I'll follow your blue hylomar suggestion when I reassemble - as you say it can't hurt.

I'll update the thread when I get round to removing the heads.