300TDi Disco, 205k miles.

bit of a long winded one this, i think i have a diagnosis but seeking confirmation of this or some general advice.

currently i have smoking on start up, this lasts until the engine is warmed up, the smoke is blue/white, once warmed up no smoke, but then if i load the engine i.e run it up the motorway for 20 mins, work the engine hard by towing or carrying heavy loads, then the oil light flickers when i idle, if i shut the engine down at this point it becomes hard to restart a bit like having a flat battery, if i let it cool down a little it starts easy and oil little flickering disappears.

now in January this year my head gasket went, i lost compression in cylinder number 4 and had a ticking/hissing sound out the gasket, as it was extremely cold around this period i ran it for about a month before i changed the gasket, not wanting to work in the cold!. it was only after this that the engine became hard to turn over when hot and oil light flickered, but no smoke.

i assumed it was an oil pressure pressure problem, since then i have replaced the oil pressure switch, oil pressure relief valve, had and oil and filter change (twice), fuel filter change, head has been completely refurbished with new oil seals and reseated valves, and another head gasket, no sign of cracks in the head, no cross contamination in the oil or water, however when the head was off i did notice that piston 4 bore was very shiny (didn't take much notice at the time), number 1 cylinder was off center.

it dawned on me last night that the shiny bore is a bad sign, because all the cross hatching's had been either worn off glazed, therefore am i correct in diagnosing that the bores need re-honing and piston ring need replacing??, im pretty sure that this would cause smoking when its cold, the tightness of the engine on restart is because of poor lubrication in the bore therefore overheating and effectively seizing the piston, i am assuming that the oil flow back to the sump would be compromised because there is no honing's left, subsiquently causing low oil levels which is why oil light comes on,

am i missing anything simple, or is my diagnosis correct? if so what is the best way to go around repairing it?

Cheers Folks i know its a long winded one but i appreciate any help

Dave

worn bores wouldnt give low oil pressure though they would make cold start harder and smoke,how do you mean no1 was off center?lack of oil to piston could occur if oil squirt fell off (it does happen)nothing to do with worn or glazed bores,sounds worn to be honest

thats the only bit i cant get my head around, oil pressure is normal, (around 60psi) but oil light still flickering immediately after being loaded, im assuming its warning of low oil levels rather than oil pressure.

starts fine, just smokey, runs a little rough, all the injectors have been changed and plugs are working fine, number one piston was almost touching the wall of the bore, probably .5 mm off the opposite wall had a gap of around 3mm, just looked lop sided

sounds worn out ,pistons have a thou clearance at best,there is more gap around the top ,but one looking different to the rest is a bad sign, rebore is about £120 new pistons £30 upwards a piece, ,bores need boring and honing to the actual new piston size