Loss of Oil Pressure

So long story short I did a rebuild on my stock 91 3SGTE down to the block, having everything machined, reused the pistons, but the crank was grind down, new propersized bearings, the head was reworked, etc etc.

I installed
ATS High Volume Oil Pump
ATS GT28RS turbo kit that includes the turbo, the bored fuel rail, the ECU tune, theromostat
New GSC S1 Cams
Supporting mods such as ron davis radiator and inject cleaning and 255 walbro fuel pump
And general maintenance items such as water pump, new seals almost everywhere, new valves
And some other things here and there

After 50 miles on the rebuild I saw my oil pressure light flickering. Saw I was losing oil pressure at operating temp. Main and rod bearings were chewed to shit, supposedly from a bad start up on the build (had a lot of trouble getting it to run, and then even when it did it was on 2 cylinders for a bit, due to a loose wire). Did another rebuild, more machining and cleaning, new-used oil cooler and a new oil pump cause of debris, and bored to .020 because we were running out of space. I cleaned the turbo best I could but running two cans of break cleaner through the oil inlets and outlets.

This time I used brad penn break in oil, assembly lube, prepressurized the oil system, and got it running a lot faster and better. Got 850 miles and saw signs of my oil pressure dropping (light didn't go off during cranking, flicker lightly under a hard pull or when idling when warm). Checked oil pressure again, and same issue. Was only making about 6 psi at halfway to operating temp, and about 30 psi at 3k rpm.

We took some bearings off, and noticed some light scouring from what appeared to be micro debris traveling through the oil system, but no serious damage as of yet. I still have to check all the bearings since I only pulled half, but not expecting to find anything different in the others.

So 2 questions:
Where could the debris come from if we cleaned or machined the entire engine? Is it possible the turbo retained it?

And where in gods name am I losing oil pressure? It is also turbo related? Could the bearings in the turbo been grinded down on the first rebuild to the point where its impossible for it to hold oil pressure? I never checked the oil pressure after the second build because I thought for sure I couldn't have any problems.

I've now owned this car for 6 years, drove it for a max of 6 months after I first got it, sunk over 10k into it, 5 years of wrench time, 2 rebuilds, and I now pretty much have a paperweight. And thats trying to do thing correctly and smartly with regards to mods and maintenance work and everything.

I'm not sure about the second question but see this quote from Koracing http://www.koracing.net/viewproduct.php ... roduct=610.

NOTE: it is assumed that the core engine did not have a rod bearing or similar type failure. If it is a rod bearing failure motor as the core, additional charges will need to be paid for a new oil pan, oil cooler, and pickup tube. These parts can sometimes be obtained in good used condition, but if not, a new oil cooler MSRP from Toyota is nearly $800. Reusing an oil cooler from an engine that is known to have had a rod bearing failure, or oil pan (gen2) from the same will result in nearly immediate demise of a freshly rebuilt motor. We check all oil coolers prior to installing for metal debris inside if supplied by the customer.

Click to expand...

Yeah I actually talked with KO after the first rebuild failure. I got a used oil cooler from a non-bearing failure engine and a used oil pan from a MR2 that was in good condition with no bearing failure.

Still no answers, even with all the research I've been doing. Pulled some more things apart tonight, found some oil on the intake side of the turbine and in between the turbo and MAF. Exhaust side of turbo was clean and didn't notice any oil on the turbo output/pressure side into the inter cooler. Is it possible this is from oil seals? I haven't noticed any smoke when its running. And I'm loosing a helluva lot of oil pressure for a small leak.

I'm also wondering if its possible its coming from the head/EGR/air system?

And does anyone know what that black splatter by the block oil outlet would be?





Looking from the turbo towards the MAF


The MAF turbo side


Intake piping between the MAF/Turbo


And the spatter. Engine was very clean when I started driving it 850 miles ago...

Since there's no oil on top of that oil fitting for the turbo I'd guess that it's leaking. For the oil in the intake I'd lean towards the head/breather system, do you have a catch can on there?

No oil catch can. I tried checking the PCV hoses, was hard to see. I think I'm gonna pull them apart and inspect them more closely and see if I can see oil coming from the block. Also noticed a tear on the MAP to Turbo pipe

The loss of oil pressure you've described is due to your bearing clearing clearances being too wide.

That may be caused by debris being pumped through them or by simply being set up too loose to begin with. Either way, focus your attention on the main and rod bearings. They are what determine your oil pressure (assuming your oil pump and pressure relief spring are working correctly.)