Oil pressure issues 2.25d

On my mate's 110 'The Dude with the 110' - he had issues where the oil pressure light would come up after a long/heavy run - suspected the o-ring on the filler cap but left it.

Recently it started coming up more often, as far as I know if he added oil it stopped it, until last week when it started coming up alot more regularly,

Had a butchers today and we suspected a leak from the oil filter, drained the lot down and stuck a new filter on and it's coming up with the pressure light after about 5 seconds now. If you rev it it will flicker but stay up (will occasionally go away)

Checked oil pressure switch wiring by disconnecting it - all ok, so no short exists in the wiring

Also dipstick connection into engine was loose, tightened it, issue still exists.

No obvious oil leaks any more,

Also he says its sounding rougher at idle than before,

He's hoping for oil pressure sender (I would too if it was mine) - I'm suspecting oil pump and the low oil pressure has probably done some damage to cause rough idle - what's everyone elses opinions?

oil pump ,main brgs ,conrod brgs ,cam brgs probably all cheap to rebuild

It's telling you the oil pressure is low. Sealing the engine won't increase the oil pressure!
Low oil pressure is usually an indication of engine wear - extra gaps in the bearings, particularly the big ends. Or it could be wear in the oil pump. Starts to show up at low revs and gets progressively worse. Time for an overhaul.

Thats pretty much what I expected, my mate is still adamant that it could be the oil pressure sender, as increasingly unlikely as it sounds......

I'll keep it updated when we find out whats kicked off, even though it does sound like we've figured it out

Have now replaced the switch, seems to have done the trick, light comes up before you crank it, as soon as it fires up its gone! Was worried about the possible bearing failiures though, time to start planning a 200tdi conv maybe...