Odd Oil Pressure Change...
Odd Oil Pressure Change... aright guys just got done building my motor, its built pretty dang loose so when we started it we expected to see low oil pressure which would be fine. we started it and at idle it was pumpin about 60psi, hot or cold, then while driving it was around 75psi hot or cold. this seemed kinda odd, runnin Rotella T 15w40 in it, i notice today that my oil pressure just suddenly dropped, going to what it should be. around 25-30psi or so at idle and about 50-55psi cruising. it had 400 miles on it or just a little less when it did this, it wasnt a gradual drop, i was driving i looked down it was 75psi or so then i look down again and it dropped down to 55psi, changed the oil and put Rotella back in it, and it changed from 25-30psi to 30-35psi at idle and then 55-60psi driving. im not worried about it, i think maybe i had a stuck sending unit or something and it finally worked loose. The motor is loose all around, mains, rods, except piston to wall clearence, the gauge before didnt fluctuate hardly any now it fluctuates with different rpms, i was worried at first but i think it was incorrect at first, and is now correct. no metal in the oil at all, no odd noises, nothing different at all just the reading is different, i think maybe the sending unit must have had something in it and it broke loose or something, but i thought i would ask on here see if anyone had this problem. its a BWD sending unit. oh also i have a LPE GM HV/HP oil pump.. Thanks guys!!
i was thinkin that, its still going down slightly, goin to around 19psi warm at idle. it hasnt gone below that, but im thinking about taking the front cover off and checking it, making sure nothing is cracked on the oil pump allowing a bleed off or something. or maybe the o-ring isnt the right one or is gettin pinched. cuz it would make sense if it slowly went down as break in or something but it went from 60 at idle to 40 then down to 20. like i said no odd noises, no metal flake, nothing abnormal at all except the readings.
i'm getting something similar. my oil is fine cold about 40 psi then it drops down to 20 psi at idle. i'm going to roll with the 10psi per 1k rpm theory on this motor. hopefully i dont trash it lol
is it a new motor? mines a new motor, i know nothing serious is wrong, but really i dont want to pull the front cover back off but oh well.. gotta fix it i got too much in this motor to be dicking around.. anyone else???
here is another thought on the o ring thing, the pump i have is alot larger than the factory one, not only internally but externally, i have a double roller timing chain also on this motor, so the pickup tube really has to stretch to get to the oil pump from it being so much bigger. im thinking that maybe it may have pinched the o-ring to one side from it having to stretch so far. sound logical?? someone please chime in!!
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I forgot to mention it last night when we talked, but try changing your oil and see what happens. Also, I would use Valvoline VR1 Racing 20W50, but I guess if you want to do a back to back comparison, you should use the same oil you are using now. We run the VR1 in every single engine that goes out the door.
On The Tree
Joined: Jun 2007
Posts: 106
Likes: 0
From: kingsville, Tx
check your oil pressure sending unit. hopefully its something easy like that or maybe the oil pump. if not, it might be just that loose. just out of curiosity what were your bearing clearences?
man i dont remember the clearences, ill have to ask the guy that help me build it, i put rotella back in it after the break in oil, its still the same and seems to maybe be slightly going down still, ill try the vr1 oil and see what it does!!
9 Second Club
Joined: Aug 2008
Posts: 463
Likes: 0
I had a similar problem and horsepower tv did also. Oil pressure was good on initial start but several minutes later it went down. They took the oil pan off and found that the pick up tube was a little cocked. They elongated the mounting bolt hole to give it some give because the o ring was not seating squarely in the oil pump.
oh yeah i forgot to say i already tightend up my sending unit once from it leaking, so i dont think it was that, i know that its nothing serious but its just kinda a pain in the *** to take it all back down to check one thing, but id rather do that than spend money on another bottom end!!
maybe try a mechanical gauge and see if it matches your electric sending unit. 75psi on start up definately seems high and if it wasnt moving when you revved it was most likely a stuck sending unit like you said..
id still take the pan off and try to get that pickup as square as possible on the oil pump where you have changed the geometry....
i think you know what you have to do, now just gotta get dirty
id still take the pan off and try to get that pickup as square as possible on the oil pump where you have changed the geometry....
i think you know what you have to do, now just gotta get dirty
yeah it would move, just not a whole lot, it would be 60psi idle and be about 75psi or so driving, but its still steadily going down, its down to below 40 at idle cold after a couple mins now, i think i have a pressure bleed off, so im gonna check it
Actually bra, your pressure seems fine. Ive had many many LS motors and they've all done what yours is doing. No problems.. Id drive it and just keep an eye on everything.