03 Explorer oil pressure drama: Ideas?

[kcblakely]

Hi All: I have an 03 explorer with the 4.0L V6; about 200K miles.

I just completed a full replacement of all timing chains and guides; Pulled engine, cleaned and milled heads, replaced gaskets, replace oil pump. Put it all together, filled it with 10/30 with a new Purolator filter and started it.

Started fine; normal oil pressure. Then, after a few minutes, pressure gauge drops to 0. I rev the engine, it pops back up. Let it sit at idle for 45 sec or so, it drops to 0.

I replaced the pressure sending unit; same behavior.

Bad oil pump? Oil too thin for an old engine? Weird electrical problem? Thoughts?

Props to 2000StreetRod by the way: his threads got me through this job!

 

[sr139fox]

Tie in a direct reading Guage at he manifold with a t fitting. That should verify pump or electronic.

 

[kcblakely]

So just to wrap this up: I bought an external oil pressure gauge (this: Oil Pressure Tester Gauge Engine Diagnostic Tester Set Auto Transmission 500psi 711221793625 | eBay) and determined that my oil pressure was indeed low. Conclusion: the brand new oil pump I put in must be bad. Installed a new one, and now pressure is at ~50psi consistently. Victory!

Aside: changing the oil pump was a lot less horrible that I thought it would be. There's a lot of bolts, so an air ratchet or (even better) a hammer driver is very useful.