MC engine rebuild - low oil pressure

[EBavely]

Hello all...

Patient:  Rebuilt 1986 MC-1 turbo engine recently installed in my 4kq.

The engine in question was completely rebuilt (by me and a friend) with a
checked std. size crank (verified by machine shop), new bearings all the way
around, rings, guides, seals, etc.

Symptoms:  Oil pressure cold is around 30-35 psi (around 2-2.5 bar), then
drops to around 10-15 psi when warm.  Pressure warning light and buzzer go
off above 2200 rpm (as designed).  Pressure does not rise much when engine
is revved.  Oil is traditional Castrol 10w30 for break in period.

I've verified the oil pressure with two different "known working" gauges and
senders and results are consistent.  The pressure still appears to be lower
than it should be.  I searched the archives and it seems to me that on a
newly rebuilt engine, pressure should be around 5 bar or so when cold.  My
rebuilt rabbit GTI engine pegs my 5 bar gauge when cold and pressure remains
strong even when hot.

I've tried inspecting / swapping oil pressure relief springs and pistons and
also replaced the senders in the block, but the oil pressure still remains
low.  Since everthing is new on the engine, I'm suspecting something isn't
allowing for pressure to build up.

Others have given me the following ideas:

1.  Ensure that the crank plugs in the galleys are still in each crank throw
(came out at machine shop during cleaning?).
2.  Make sure all piston oil squirters are in place / tight
3.  Problem with oil pickup (obstruction in screen, loose tube, no clearance
with pan)
4.  Excessive clearance between crank and bearing caps (doesn't seem to be
likely...I hope)
5.  Flakey oil pump (?)
6.  Obstruction in oil galley between oil pump and pressure senders

I don't hear any clunky, expensive noises when the engine operates and it
runs very well, so I'm hoping it isn't too serious.  My next step is to drop
the subframe, pull that trans / flywheel cover, drop the oil pan and inspect
everything I can.

Any other ideas or things to check?  Obviously, I wanted to avoid getting
back into the bottom end so soon after the swap... kind of bums me out and
lets some wind out of the sails.

Thanks guys...

Elliott Bavely

86 4ktq
83 CGT
81 Coupe ITB
88 80 Fwd
83 GTI FSP
83 GTI 16V
90 VW Cabriolet