pferris

iTrader: (2)

I am having an issue with low oil pressure, and air in the oil. The oil pressure is around 10psi at idle, possibly lower. This is tested with a manual pressure gauge at the pressure sending unit port. After running for less than 30 seconds, there is a large number of air bubbles on the dipstick.

This is a new motor build, with probably 250 miles on it. Bearing tolerance is stock, and oil pressure was good for the those miles. Bearings are all new, and I am running a melling 10295 oil pump. The build is a rebuilt stock bottom end, save for arp rodbolts(resized) with stock 799 heads, and a torquer v4 cam.

I have tried replacing the oil pump with a new 10295, and the pickup tube with a brand new GM one. I am 100% confident the o ring is not damaged, as it has done this with 3 separate o rings. I have cut open the oilfilter used, and there was no excessive bearing material. This issue remains with two different oil filters.

I am out of ideas, the air in the oil had me thinking that the issue was with the oilpump, or somewhere before it, but everything there has been replaced and the issue remains the same. Any recommendations would be appreciated.

jermzz

iTrader: (18)

What's the oil pressure do when rpm rises? Does it stay within spec?

pferris

iTrader: (2)

The oil pressure raised to about 15-20 at 2-2500rpm cold on the manual gauge. And raised to a high of maybe 30 at 4-4500 when I was driving and first experienced the issue.

The oil pressure prior was about around 40 for a warm idle and would rise to 70+ and obviously there was no air bubbles in the oil.

Darth_V8r

iTrader: (4)

Bit of a long shot on this one, but it could be your oil pan gasket. There is high pressure oil going through your oil pan gasket to get to and from the filter. If that gasket blows, it'll either vent outside and squirt the headers (like mine did) or inside and just refill the oil pan. Anywhere oil gets out, air gets in.

My oil pressure increased from 25 warm idle to almost 40 warm idle after oil pan gasket replacement.

pferris

iTrader: (2)

That is possible, but not too likely. The gasket was new, and then the pan was off to change the pickup, and I didnt notice any damage the gasket. Something I can check though.

Darth_V8r

iTrader: (4)

Yeah, it's a long shot for sure. but sort of like looking for your keys. once the usual stuff checks out, you start checking weird places.

pferris

iTrader: (2)

Yeah, I agree. I'm probably going to pull the motor this week, but my idiotic self separated my shoulder last week mountain biking, so I'm trying to get a good idea before tearing it completely apart because working on it requires calling friends. Hahaha

Taxman20

iTrader: (11)

You might have a crack in the pickup tube.

pferris

iTrader: (2)

My thought until I replaced it and the issue continued

dave04da

iTrader: (2)

Did you reuse the old cam retainer plate?

one fast zo6

iTrader: (490)

In for info

pferris

iTrader: (2)

No I did not, and all other gaskets in the motor were replaced with the rebuild as well. And a failure of that seems unlikely as it made it ~250 miles.

Pugbug288

Double check the front oil gallery plug and the little oil barbell.

farmington

iTrader: (14)

air bubbles should mean that there's a leak of some kind on the suction side. pickup seal, pump oring, pan gasket near the pickup tube, etc

Taxman20

iTrader: (11)

Thats why I mentioned the pickup tube. It should be on the suction side. Only way to get it to aerate on the pressure side would be at a high pressure location like the pan gasket near the oil filter. So it has to be a hard spray. It might even be an issue with the oil pump itself. Could be cracked in the housing.

pferris

iTrader: (2)

That is exactly my thoughts, but there is a brand new oil pump, brand new pickup tube, and brand new o ring. The oil pan gasket remains the same though. The issue has not changed after having it apart to replace the parts, and reassembling.

.boB

iTrader: (1)

Sucking air somewhere. If the O-ring, pick up tube, and pump are OK, look at the gasket to block surface. Also, check the pick up to pan clearance - should be about 3/8".

1970camaroRS

iTrader: (8)

Had the same symptoms when a cam bearing walked out of the journal.

Darth_V8r

iTrader: (4)

I'm gonna share one of my screw ups. I dropped the oil pan about an inch off the block to reseat that stupid o-ring. Then I wasn't able to get the gasket off. I had thought I'd be able to slide it around the pick up, but never expected someone would rivet the damn thing to the pan. At the time still had the stock K member also, which really made working in there terrible. So I replaced the o-ring, put the pan back on with the original gasket, which had completely flattened out and had cracked right where the oil feeds and returns for the oil filter, so I had the exact same symptoms as I had before.

Then, when I swapped to a tubular K I went ahead and dropped the pan and replaced the gasket, which actually fixed the problem.

If the oil pan gasket doesn't fix it, the pump housing could well be cracked.

pferris

iTrader: (2)

Well, As I am confident that the oil pump is fine(As it has had one that looked fine replaced with a brand new one) The pickup tube is fine, and confident the o ring is not pinched, it must be the the pan gasket then. Hmmm I wish I looked at it while changing the pickup tube, but it didnt cross my mind.