5 Liter Eater

Yesterday on the way to lunch I noticed my idle oil pressure was ~15#. When I rev it up the pressure builds to ~40#. When I came out and started it there was ZERO pressure for ~10 seconds after the gauges were zone sweeping. After that it went back to the same low idle pressure.

When I went to go home it was similar. Zero for ~10 seconds, then up to ~30# until it started to warm up, then down to ~15# at idle. Oddly, about halfway home the idle pressure started to act normal again, staying ~25-30#.

I just changed the oil on Sunday and used Penzoil Premium synthetic 10W-30 and a Mobile 1 oil filter. Both unknowns as my standard is Mobile 1 5w-30 and Purolator Pure One or Fram ExtraGuard filter.

From my research here and on LS1Tech these symptoms have stemmed from anything from oil and filter to oil pump to cam and/or main/rod bearings. First thing I'm going to try is to change the filter, then the oil. It seems unlikely either would cause this, particularly the oil, but it's cheap enough to give it a shot before I yank the the rack and whatever else I need to in order to replace the oil pump which seems like the next likely culpret.

Thoughts? Comments?

Mez

Sender? Loose connector or sender itself. I don't have anyexperience however with this problem so take my thoughts for what they are worth. Free

5 Liter Eater

When the sender goes south (and they do) the gauge pegs at 80 PSI so I don't think it's that although I may look at that if the oil/filter/oil pump don't fix it. I just hope it's not bearings. The motor is not making any abnormal noise at all and oil and H2O temps are normal.

cranky

check your pressure with a mechanical gauge. tap into the side of the block oil gallery. then decide what to do.....................

dennis50nj

if it was bearings it wouldn't fix itself and read normal, probably a malfunctioning relief valve in the oil filter

5 Liter Eater

That's my hope/thought. Just paranoid about engine damage due to my now ~800 BHP.

Robls6

When it showed no oil pressure was the motor noisy? (lifter clatter)

5 Liter Eater

No, no noise at all.

mike.brown

It can also be due to the wear of bearings. Pressure is not created by the oilpump itself . Oil pump provides the flow and the resistance to that flow is the cause of the pressure and resistance is created by the amount of clearance between the bearings and crankshaft journals. so wear of these also can be one of the reasons.

don7790

You must make sure that you have low oil pressure and not a defective oil pressure sender.

5 Liter Eater

Well it looks like it was the oil filter. I put an AC Delco PF-46 on and it instantly came up to >40 PSI cold. I'm sure it wasn't great for the motor to have those ~1/2 dozen starts since I changed the oil where it took ~10 seconds to develop pressure. Maybe I'll send the oil off to Blackstone to see if the bearings are deteriating.

So I cut the filter open and I didn't see anything that looked amiss. What I didn't see was any anti-drainback valve? Can't say I have too much knowledge of the inner working of oil filters, I'm no bobs-the-oil-guy, but I cut open an AC Delco PF-48 (which I mistakenly bought to replace the Mobile 1 filter) and it has one. From the limited research I've done it should not be needed in our motors because the filter is upright and at the lowest point of the oiling system.

PF-48 cut apart:


Mobile 1 cut apart:


PF-48 bottom:


M1 bottom (no drainback)?:


PF-48 inside (can see the spring for the drain-back):


M1 Inside (no spring, plunger, nothing):


Again I'm no oil filter expert. There didn't look like anything wrong with the filter when I took it out other than it doesn't appear to have an anti-drainback valve. Like I said, the pressure kind of normalized when I got halfway home yesterday with the M1 filter so it could not be related to the filter at all and whatever it was fixed itself, at least temporarily. I'll check back if the pressure drops again.

Robls6

I have a Mobil 1 on my car (for the past 40,000 miles) and have never had a problem. There is no "drainback" after the car shuts off from the oil filter.

davekp78

It's a pressure relief valve- not drainback. You have an '05 non Z06? You should be using the 46 filter, without the relief valve.

dennis50nj

as i thought. the purpose of the valve is if your filter gets clogged with so much crap, your oil pressure will go low then to 0, then the relief pressure valve opens and bypasses the filtering of the filter, this takes some time at each start up. bad bypass valve or the filtering material is bad, clogged

5 Liter Eater

It's an '05. I bought the 48 because I remembered that there was a bigger and/or better AC Delco filter that could be used in place of the 46. I was searching CF on my phone at the parts store and read that the 48 replaced the 46. I thought it was just a redesigned 46. Didn't realize they were actually different. The diameter of the hole the filter screws onto is larger. I didn't look at the 46 I put in to see if it had a relief valve.

The M1 filter didn't look clogged up to me. I'll be keeping a close eye on the pressure.

dennis50nj

it probably wasn't clogged, maybe bad filter paper not porous enough, or a made employee who sprayed it with clear lacquer or shellac, or just a bad relief valve, or just the wrong filter, if you didnt hear any taps, you didn't hurt if you haven't noticed any pressure readings lower then before

stevette17

so is it just the ls2 ls3 getting lower oil pressure?
what other filters are causing thing problem?
what filtration does mobil 1 and k&n have?

RoadRebel

Stuck oil pressure relief valve in the oil pump? Sometimes the get debris in them and will hang wide open dumping directly back into the pan. They will also make it hard for the pump to prime when stuck open, sorta like when you have a hole in a straw.

Phil

5 Liter Eater

For me it went away as soon as I changed filters so I don't believe it was to do with the oil pump. Although I didn't see anything obvious about the filter that would have caused it.

Medicdiver

I work at a dealership and have had this same issue. The most recent one reminds me of a Lexus that had an oil change at a quick lube place, with a MObil filter. Oil pressure was reading 5psi, and confirmed low witha manual guage. Found it to be a plugged oil filter media, so changed the filter to a Factory Toyota one. Once Oil was changed to remove any possibility of dirt in oil, car was fine. Have seen the car several times since then, and engine suffered no damage.