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UPDATE: got everything back from the machine shop and nothing that really stands out as the problem. I have theories, will get to them in a minute. The pickup has no holes, tested it under water with balloons on each end, no bubbles. Pickup tube to oil pan clearance is also G2G.
The pump does show some carnage. Either the pump was failing or it was sucking air. The pump housing is chewed up pretty good with corresponding wear on the gears. This pump had maybe 10K miles total on it. The gauge twitch didn't begin until first rebuild and was steady when installed on the bone stock motor.
Now to the theories.
#1 As you can see in the pics I had the pickup tube where the hold down clamp is floating. With that clamp tight against the pump housing, the pickup tube is free to move around what I consider to be a lot. When the pickup tube was bolted to the windage tray studs it put the tube at a bit of an angle going into the pump. The odd angle crated just enough space on one side of the o ring to allow the pump to suck air.
#2 The pump sucked up from trash at some point which began a self destruct sequence where the pump starting to inject shredded pump housing into my bearings. Doesn't explain the aerated oil or the noisy valve train though.
I bought a new pickup tube, which is the other style with the oil pump attachment tab welded to the tube. Installed with a factory oil ring into an LS6 pump. Working on getting it all setup for testing on the engine stand and will report back. Everything from the pump upstream is new, I should be ok to test fire this engine right? I can't see how the issue is downstream if the pressure was indicating so high.
yeah, i wonder if the pump sucks all the oil until it's just air (gauge drops), enough oil returns to the pan so it gets oil again (gauge increases)... repeat...
agreed, it could be different reasons. OP mentioned a HV oil pump, so that's a possibility given others experiences with them.
I considered this, but it did it at idle, with a deep truck pan, and 6 full qts of oil. Also, I had this same pump in the engine before I built it up, it didn't do the twitch or wreck every then.
I agree, this time he has to cover all bases or pay the consequences. Sometimes its not so easy to solve a simple problem like this because you can't find anything obviously wrong BUT the gauge ticking 5psi all the time is a dead giveaway something is way wrong.
I thought the same thing. Take a minute and search this forum for twitching oil pressure and see how many people say it's normal, a lot. After researching I convinced myself it was the sending unit or a bad wire, which to be fair is very common. A mechanical gauge is a must when troubleshooting this kind of stuff.
Well never did really nail down what the cause was, but I did assure the engine isn't doing it again with the new pump and pickup.
A picture of my oil primer is below. Standard air pressure pot type primer. I pushed 6 qts of oil thru the primer, then hooked my starter up to a battery. With the air pressure off the pressure pot, the engine oil pump would pump oil back into the pot Basically just pumping it up the line I used to prime it. The port I have the primer inserted into is right after the pump. With the starter running the oil pump was pumping oil thru the clear hose into the PVC pot. At first there were some air bubbles, but after letting it run for a little bit and closing the ball valve on top of the pot just enough to keep back pressure to oil the bearings, the oil ran perfectly clear with no air bubbles.
I then pushed the oil from the pot back into the engine and repeated. On the last run I had no air and a steady pressure gauge. I then closed off the ball valve feeding into the pot, which essentially is like putting the plug back in. Ran the starter again, and bam 35ish PSI rock steady. I took 2 videos and will link them below. The whole process is overkill, but at least now Im sure I won't have aerated oil on start up.
Hopefully this thread can save someone from making the same mistake I did.
I'mma tell you what I would do, use a pickup tube truss start the engine and listen for lifter noise. Lifters stay quiet oil should be air free, put some light load on the engine 1500 rpm and listen watch for air bubbles. No bubbles quiet lifters then run it harder. If at any time you hear lifter noise stop and check for bubbles. At least this way you shouldn't do any damage. If it stays quiet you should be ok. BE SURE YOU USE THE RIGHT O RING FOR THAT PICKUP TUBE. If at any time the lifters start making any noise stop and check the oil.
One more thing, if you run WOT and afterwards the lifters get loud you know something's up. Don't ignore it.
looking at that plate ( the 2 bolt thingy ) above the filter.....it looks flat in the pics...mine ( stock ) is not flat but has some what of a passage way to flow oil.....is that a stock ( gm ) oil pan ?
looking at that plate ( the 2 bolt thingy ) above the filter.....it looks flat in the pics...mine ( stock ) is not flat but has some what of a passage way to flow oil.....is that a stock ( gm ) oil pan ?
That's just a block off for the oil cooler lines. It's only there to prime to the engine. Once it's in the truck the oil cooler lines will go there.
Ya know the condition of that oil pump could have certainly been causing air to get mixed into the oil. May have been the entire issue, Air will get pushed into any place its worn like those gear housing surfaces. I've found many oil system full of air bubbles from that very condition.
One of the reasons its so tough helping someone online without seeing everything.
01-21-2018, 11:22 PM
