Land Rover Repair: knocking when cold, piston skirt, coolant loss

Question
Giday John I own a 1998 p38 in very good order i also have own diagnostics for the car [rovacom] everthing is great but for one thing first start in the morning i get a echoing knock that seems to come from the phelum chamber strange if i let it idle for 60 secs it is gone can this be water in leaking into a cylinder[hydraulic lock] this has got stumped because there no faults coming up at all thanks john by the way great site cheers

Answer
If it knocks for a minute you could have something a little loose in the motor, perhaps a worn or partly collapsed piston skirt. You could also have lifter or rocker shaft trouble.  Sometimes the lifters take a while to fill.   It may or may not lead to trouble down the road.  If your vehicle has a catalyst the converter could be noisy.  Finally, you may be getting confused by a exhaust manifold leak.

I suggest listening with a stethoscope to see if the noise is inside.

In my experience liner problems are usually associated with coolant loss and overheating, which you do not seem to have

If you conclude the noise is inside the motor you might try running Mobil 1 0-40 oil and see if the thinner oil cleans out the lifters and thereby reduces or fixes the noise.  If the noise is from a worn piston that will have no effect.