Land Rover Repair: overheating, block sealer, head gaskets

Question
QUESTION: 2000 disco 2 over heating head gaskets changed thermostat changed.
mech pressurized cylinders one at a time #5 caused bubbles in overflow tank any help would be great

ANSWER: Cylinder #5 gases entering the cooling system would indicate that the cylinder sleeve is either porous or, more likely, moving, thus, allowing the breach. The cylinder head has no direct water jacket at this point, so it could only be a failure of the block assembly. This is a very common failure.

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QUESTION: could the sleeve move olny after block reaches certain temp
or if sleeve is porous how can i test to determine which is real prob .thanks

Answer
The cylinder liners normally only begin to move once the engine has warmed up, at which time, they often have a pronounced knock.  90% of the time the cause of coolant entering the block is a slipped liner.  You may be able to have it replaced, but you are probably better off replacing the block.  You can only see a porous liner by removing   the cylinder head; you would see a water mark. If this is the case, you can try some block sealer, but I have had very limited success with that.  Otherwise, you will have to replace the block.