J0SH

iTrader: (1)

Alright guys, this is turning into a real pain. I've been trying to hunt down this low oil pressure problem for weeks now. Cold oil pressure is around 55 psi. Warm drops the pressure drastically. I have chased almost every possible cause with no help. EXAMPLE. After I thought I had the problem solved I installed the motor again (Its back out now) Cold idle 55 psi. after 10 minutes of idle the pressure was down to 21 psi. I drained some oil and checked the temperature of the oil. The temperature was around 120 F. Not nearly high enough to see a drop like that IMO. If it would've continued to warm up its definitely would keep dropping.
Also I have changed weights of oil multiple times. with 15w40 It will ride at 15 psi HOT. With 5W30 it gets as low as 5 psi. Way too low for me to be comfortable with. it should definitely be higher with 15w40.

The engine is a fresh rebuild, with only a few thousand miles. I recently installed a new turbo setup when the motor went in. I assumed I was seeing lower oil pressure due to elevated oil temps but this isn't he case. I have been chasing my tail on this for awhile now. I need a little help, here is what I've done so far.

Replaced oil pump with melling standard volume high pressure a little boost but not much help. I also threw in another ls6 oil pump I had sitting around just to reassure myself - no help. I also verified the pickup tube is clean and has nothing in it, or blocking it.

Checked O-Ring multiple times this IS NOT the problem. Tried dealership one, and ones delivered with melling pump.

Check main and rod bearing clearance with plastigage. Mains came in around .002 to .003. rods a little more tight. .0015 to .002. Bearings looked great. Of course with only a few thousand miles they should.

Every galley plug is in, barbell plug is in, changed rear gasket, changed cam plate with a new gasket. Nothing is helping.

I have looked at all my cam bearings and they don't look bad. (When I installed the cam after about 100 miles I changed the oil and found "stripper glitter" in it for a few oil changes probably 500 miles total. But the bearings do not look worn and are properly installed I looked at the cam bearings with a borescope and they were all centered like they should be. A few marks where I installed and removed the cam several times. Nothing that will catch a fingernail though. Possible maybe too much material is gone from them? They look great to me.

The lifters do have some "slop" in them. They will not stay up in the trays at all. Is it possible these are bleeding too much oil off?

I feel like Ive checked almost every possible thing but I've got to be missing something. Someone help me out, getting tired of chasing this. I can supply pictures of whatever anyone wants to look at.

nzgreenfox

oil intake sucking something in after a few minutes running and then it moves back into the oil pan with the engine stopped?
Faulty oil pressure gauge and/or sender

J0SH

iTrader: (1)

I should've noted. When motor was rebuilt a new sending unit was installed. I have also replaced it again thinking it was bad. Oil pressure has been verified with a mechanical gauge also.

98cherrySS

iTrader: (2)

What lifters were used? In the past I have built a temporary oil reservoir and mounted to the pressure sender orifice to prime the motor. I discovered the oil galley freeze plug in front was leaky. Probably not 30 psi leaky but leaky none the less. Did you follow the oil galleys and check for cracks?

J0SH

iTrader: (1)

Ls7 lifters, I shined a light in the galleys but nothing caught my eye. I'll put the borescope down them though and see if I can find anything.

98cherrySS

iTrader: (2)

I see you checked the cam bearings already. I know that a walking cam bearing has caused this exact issue in the past. Especially at the rear. May be worth a 2nd look. Also may be worth double checking the barbell o-ring and barbell depth as well. I'll try to think of some other possibilities.

J0SH

iTrader: (1)

Cam bearings are all centered in the bores and the oil holes are all lined up. None have moved and look to be properly installed in the middle. As far as the barbell goes it is in place. This last time pulling off the rear cover I was able to push it in further just a hair. It could've been leaking but I don't thing it could leak that much. It has the o ring and everything in place just wasn't quite flush. I'm not thinking it's the problem

Darth_V8r

iTrader: (4)

Pressure relief valve sticking open? Malfunction of the bypass valve in the filter housing?

J0SH

iTrader: (1)

Pressure relief valve in the oil pump is fine. The Melling was slightly scuffed. One reason why I threw in an extra oil pump. No help. As far as the filter bypass it feels fine. I'm not sure that could cause a low oil pressure problem, but I could be wrong

warriorpluto

iTrader: (2)

You mean the ls1 cars have the bypass in the filter housing too? I know the 3.8 fbodies had that valve go bad and ruin the engine.could this happen on the ls1 too?

Darth_V8r

iTrader: (4)

yes the ls1 has it too. All engines do I think. It's a fail safe if the filter plugs up. Josh, it's not likely to cause low pressure but since you've covered the usual items I tried to think of an unusual item

chevy1224

iTrader: (2)

LQ4 Overhaul manual states 6 PSI is the min at hot idle. You may be just fine, just different than you are used to perhaps? I'm sure you can look it up for your specific engine as well.

Majestic9C1

iTrader: (19)

what kind of PCV system are you running?? and do you have a catch can at all?

kolmjhtyr

I have also replaced it again thinking it was bad.

Tranz Zam

Technically he'd probably be fine, but something isn't right here. I've never had an LS that didn't produce good oil pressure. Hell my 160k mile LS1 still cranks out 35-40 psi hot.

J0SH

iTrader: (1)

I can't live with the 6 psi at hot idle. My personality just won't work with that, and something is going on its not right.. The car has no pcv system. The block is all vented through filters so no vacuum on the crankcase at all. I was having problems pushing out oil under high boost so I did away with it

RockinWs6

How are you measuring the oil pressure? Did you replace the cam retainer plate?

J0SH

iTrader: (1)

Retaining plate has been changed with the summit version. Measuring with mechanical and oem oil pressure sensing unit. Both match.

Darth_V8r

iTrader: (4)

Have you replaced the entire pick up tube? I know it seems silly, but compare it to having a hole in your straw while drinking a side at McDonald's. You get less soda due to sucking up air. There might be a hole like a bad solder joint near the bottom of the tube. As long as the hole is submerged (cold start) you get good pressure. When the oil level drops, the hole gets exposed, leaking in a bunch of air and almost acting like its losing its prime.

A bit out there I know but you've checked the normal stuff.

RabidStreetRacer

iTrader: (1)

which O ring are you using on the oil pump, there are 3 different ones and that can make a huge difference if using the wrong one.