just for fun ...what weight oil? where is the sender located?

It's 10W-40. It is T'ed off of the stock port near the oil filter. The oil feed for the turbo is also T'ed off here. The oil temperature transducer plugs the end of the 2nd T fitting. The turbo has a restrictor installed. See my awesome artwork for reference.

https://www.miataturbo.net/attachmen...1&d=1351654650

I suspect if the oil pressure is near 0 psi (real not gauge error) for any length of time the damage may already be done. More run time = more damage. :-(

I've been there too. One one build, Dirt in the crank oil passage way trashed a rod bearing. Engine went from 80 psi to 10 psi in the first 10 min after startup. Oil pan was full of chips. Fix included sending the crank out for a polish, new bearings, a real good clean, etc. Good luck...

Remove oil cooler sandwich adapter from the equation. I just figured out this morning that my cooler and all of that hose puts too much drag on the oil when cold (it got down to a frigid 60 degrees last night). The relief and bypass open up leaving me with 12psi @2200rpm during warmup. Once it starts to warm up one of them suddenly closes and it jumps up to 38psi and then as it gets completely hot it settles around 22psi at low idle. I think larger diameter cooler lines would reduce the drag a bit. I've probably got 8-10 feet of hose that the little pump wasn't designed for.

Try it without the sandwich and see if it acts normally.

And just having done some research on oil filter manufacturer's sites there seems to be some variation between manufacturers regarding the bypass valve pressure settings. Wix had 8-11psi and one of the others (can't remember who) had 14-18psi. Most have been unlisted.

Re oil filter valve... There are 2.

The "bypass" is intended to permit oil to continue flow even if the oil filter element is totally blocked. (think of someone that never changes the oil in 40,000 miles. Lots of dirt prevents the filter element from flowing oil...) for most of us, this never happens.

The "anti back flow" valve is intended to prevent the oil filter oil from slowly draining through the engine (e.g. Past the Oil pump clearances) when it's not running. This could take hours to empty the filter can of oil. Once the filter is empty, the oil pump on cranking and startup will take longer to reprime the system with oil. This delays time to reach oil pressure (dry start) and is a high wear condition.

The Bypass valve is typically at the end of the perforated tube that runs down the center of the filter.
The Anti drain back valve is a rubber disk immediately under the circle of holes around the perimeter of the mounting face.

Also as noted earlier, trying to push oil backwards past the anti drain back valve will likely have a very high pressure drop. Measuring oil pressure down stream of the filter (in the standard gauge port) will be lower than on the pump side.

Filter and oil system are completely stock except for the T off of the pressure port, obviously. The remote adapter was the first thing I removed when I noticed the problem.

This is basically how it stands now...hot idle hovers around 0 on the mechanical gauge and pressure will not exceed 37ish psi when hot. It basically gets there somewhere between 4000 and 4500 rpm and just stays there.

Some oil filter pix. (none of the filters I use are listed)
Indicates oil filter construction.

http://www.ford-trucks.com/ford-manu...Comparison.pdf

Zero isn't good. Is it possible that the relief valve on the oil pump is hung partially open?

I won't know that unless I tear apart the engine again. I think I'm at the point where it needs to come out, though. Not much left I can think to try with the engine still in the car.

The Oil Pump pressure release valve has unfiltered oil (The oil filter is downstream). If there is something large passing throught the pump, dirt or filings -the valve could be jammed open... is this enough to loose all pressure? unknown to me...


Pre engine removal inspections:

Pull cam cover, see if there is any oil reaching the head,
Check surface of lifters, cam lobes for wear,
Pull one or more cam bearing caps see what the cam bearings look like... The cam has 1/2 the speed of the Crank and typically has less wear.
Remove oil filter, open the can and look for filings and bearing chips,
drain the oil through a kitchen strainer to collect filings,

That is a very good possibility. Been there, done that, and the reason I've removed the factory pressure relief valve and am using an external one.

Didja put the oil squirters back in?