Hello, new here and need some help.

So In the past 5 months I have bought, rebuilt, and installed a lq4 from a 2000 suburban 2500 into my 1999 classic obs truck. Went through everything in the motor. Only parts that weren’t brand new were pistons rods and crank. Everything else brand new, bearings, hardware, every little thing BRAND new, all torqued to spec. Got it installed and upon first start had good oil pressure (35-40 psi idle, 55ish at 2k). Motor ran for the 1st hour between idle and 2500 rpm to “seat the rings”. Decided that if it was gonna blow up that it would have already occurred to off it goes to the exhaust shop (hauled not driven). Spent 500 bucks there and took to get tuned (once again, hauled) go to pick it up the next day after the tuner said he was finished and I took it for a drive with the tuner to make sure all was good and it’s started great and had 30-40 psi at idle and go down the road about 3 miles and oil pressure started to drop. More and more til barely readable on the gauge, absolutely 0 knocks or sounds what so ever and it ran for 5-10 minutes like that (I know, dumb idea). Got it towed home and hooked up a mechanical gauge and reads 10-15psi cold at idle and drops to 2 as it warms up (again, absolutely no noises at all) pulled oil filter and there is silver dust and a few small silver flakes about the size of pepper. Nothing crazy at all, like I said no sounds AT ALL. I’m clueless and very aggravated at this because I made sure during the reassembly that I did everything by the book and to the best of my ability. I used the fat o ring from my felpro kit Only thing internal that I am hesitant of is the oil pickup tube moved 1/8 of an inch up and down when the pickup tube was bolted just to the oil pump but didnt feel like the oring came unseated when I moved it. When I put the 2 windage tray nuts on it it didn’t move at all. I’m blown away and could use some help to get my truck back on the road so I don’t have to look at it sit in the shop anymore lol. The block was not hot tanked I honed it myself so there could be sludge but I haven’t seen any in the first 2 oil changes. Any help is appreciated. Thanks!

 

The silver "dust" could likely be from all the work you did previously. Like honing the block, the rings seating against the cylinder walls, parts just wearing in.

If it was a glitter factory, then you'd have some toasted bearings.

It's possible you got a bad new oil pump. I think you'd need to at least pull the timing chain cover off to look at things. Make sure the camshaft retaining plate is tight as well, that could bleed all oil pressure too.

 

if it was the oil pump or retainer plate why would it have oil pressure and then lose it? The oil pump is a brand new melting. The retainer plate makes sense but I figured it would not have any oil pressure at all if it was bypassing through there

 

The bypass valve on this style oil pump can stick even on a new oil pump and cause a loss of pressure.

 

I was browsing the forums and saw someone mention an AFM oil pressure relief valve COULD be an issue. My wife's Suburban does have AFM, however I did buy a device that plugs into the OBD simcasts port to disable AFM. May be you should replace this valve.

 

Did you use a Melling 10295 pump?
If so, we have had several of them with issues.
remove the pressure regulator cap, spring, and the plunger inside. Clean them all up. I use a Scotchbrite pad on the plunger deal and make sure it's slick.
Coat everything with some oil and assemble it. Add a couple or few #6 washers in the plug.

Go ahead and use a new oring and use oil on it before seating into the oil pump.


If that doesn't fix it, I'm lost right there with you.

New filter and see what happens.

 

Only the 2007+ oil pans have those pressure relief valves inside the oil pan.
Using a 14mm oil plug will solve that only if you are using normal lifters. Don't plug it if you decide to go with the DOD junky lifters.

 

I used a melling m295 standard volume replacement. Do these have the same issues?