Land Rover Repair: 99 Discovery Series I, low oil pressure, rod bearings

Question
John,
You previously suggested replacing main bearing caps and rod bearings to correct the low oil pressure light I am seeing at idle, after warm up. As for the main bearing caps, I understand that only the caps can be removed and replaced with the engine in the vehicle, but is this sufficient? Are the oil passages in the caps, and will replacing these, and not the block-side bearing halves not cause more problems? Have you performed this same procedure with positive results?
Thanks!

Answer
There are no galleries in the caps, and yes, you can replace just one half but actually when you remove the front cover the crank comes loose enough that you can change both halves of all but the rearmost shell.  And of course you can do the rods and overhaul the oil pump.  That certainly gives good results, but at my shop we generally recommend overhaul of the motor because the symptom you describe is really a sign of a worn out engine.  Still, bearing replacement will buy you some time.