BIG PROBLEM.... oil pressure go bye bye??
BIG PROBLEM.... oil pressure go bye bye?? Problem started directly after a race. I hit her with a wot punch and everything was fine until the upper rpm's. The car felt like it wasnt going to shift (kinda just seemed like it was taking too long) so i let out just to be safe. Shortly after i noticed my oil pressure was starting to take a ****. Went down to probably 7-10psi. Got off the highway right away and shut her off. Oil level was fine so i started it up and limped it to the nearest gas station. Pressure wasnt coming up at all so i parked her for the night.
Anywho, finally got her back and trying to pinpoint the problem. When completly cold the oil pressure is fine (40-50psi) and sits there at idle and rises with throttle application. By the way, bout 1.5 months ago i replaced the pump with a melling hv-155 i believe. But like i said pressure is fine at start up, but with increased engine temps the pressure starts to drop. At operating temp its all the way back around 7-10psi again. Car seems to run fine and when oil pressure was good i gave it a little and it runs smoothly. No loud knocking or tapping. Valvetrain looks fine. I also checked the pressure directly off the side of the block and it read the same.
Im starting to think that it has something to do with the pressure relief spring and then when it finally heats up the oil is thinner and is going right passed it. My gm teacher seems to think that its something major along the lines of a bearing... main or cam. But he pretty much says that theres no telling til i tear her down.
What does this sound like to you guys???
Anywho, finally got her back and trying to pinpoint the problem. When completly cold the oil pressure is fine (40-50psi) and sits there at idle and rises with throttle application. By the way, bout 1.5 months ago i replaced the pump with a melling hv-155 i believe. But like i said pressure is fine at start up, but with increased engine temps the pressure starts to drop. At operating temp its all the way back around 7-10psi again. Car seems to run fine and when oil pressure was good i gave it a little and it runs smoothly. No loud knocking or tapping. Valvetrain looks fine. I also checked the pressure directly off the side of the block and it read the same.
Im starting to think that it has something to do with the pressure relief spring and then when it finally heats up the oil is thinner and is going right passed it. My gm teacher seems to think that its something major along the lines of a bearing... main or cam. But he pretty much says that theres no telling til i tear her down.
What does this sound like to you guys???
yeah man i have been there.. my first lt1 motor i put in my chevelle did the exact same thing when i was racing on the highway. it was my daily driver and i thought it would be alright because it did have 40-45 psi cold but only 10 ish warm...lets jus say your in for a rebuild. mine didnt last the week after that. sorry to bear some bad news but be prepared for a rebuild.
A high volume pump is a no no unless you have a 7 quart deep sump pan. Your teahcer is right I am sad to say, but for ***** and giggles you can check out your oil sending unit and gauge by utilizing a mecahnical pressure gauge to see how accurate it is. I can't say it any better than what your teacher has.
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Well im hoping its just a problem with the pump, and seeing as how i really havent driven it much with low pressure i would think the engine is fine. But like i said it runs smooth and everything just keeps lossing psi.
jay rich: sheered the teeth where>? Up top where the pump drive meshes with the cam?
jay rich: sheered the teeth where>? Up top where the pump drive meshes with the cam?
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Verdad Gallardo Also what internal engine part can actually cause my oil pressure to be fine at a cold start up, but by running temp be extremely low, besides the pump itself? If it is a bearing or something how would it cause this to happen? By the way i already replaced the sending unit and used a mechanincal one on the side of the block to be sure.
If the pump pickup came off, not likely cause you have oil pressure until warm, that would cause loss of pressure. Worn bearings or spun bearing will do the same and now that you have clarified it, thats where I would be checking.
If it were the cam gear/oil pump drive gear you wouldn't have any at all.
If it were the cam gear/oil pump drive gear you wouldn't have any at all.
There is too much play in the bearing and it is not allowing the engine to build up oil pressure. I have heard of guys having lower pressure though. I would say to drive it carefully and see what happens.
When oil travels through the engine it goes through the journals in the block,crank,etc. and if for example your number 4 rod bearing is bad,( lets say its to thin/wornout) then it will relieve pressure and by the time it gets to the cam bearings ( were the oil pressure sending unit gets its reading) you only have a little .My advice would be stop driving it and pull the motor and have it gone through before it eats up a crank or if you still want to drive it then change the oil with 20w50 its thick and might not let so much sneak past the bearing but that is really like a very short term fix.
My take is bearing related also. You have oil clearance tolerances in your bearings. If these are changed somehow, your tolerance could be to little which won't let enough oil in or to too much which will allow oil to pass righ on through which can lead to the bearings spinning and possibly staking on top of each other(does really bad things to the internal parts, I had this problem with my 85 Camaro with a 4bbl. 305.). I'm shooting for the second possiblilty. Another way to check, would be too see if you are getting oil up to the rockers. This might actually help you diagnose the severity of the problem.
I do believe it will be your bearing..when I spun mine it did the exact same thing your is doing to a T and my bearing was ate up...do yourself a favor and stop driving it before you need a new crank like mine did..I drove it too long with a bad bearing..the thicker oil will help for a minute but it wont last long
What to do, what to do?
She is my daily, but i have been managing to get back and forth to work/school other ways. I think i am either going to get a bike and slowly build her up with big cubes and big boost. Or im gunna do a basically stock rebuild for the time being.... Hmmmmmmm. I duuunnnoo.
my oil pressure has been that low for the last 12k it has 118k on it now and i still beat the hell out of it. i do run pennsoil 10w40.. 55psi cold, taps out at 65 psi if i leave it in first around 3k (C0ld) hot idle is 3psi and will go to 45ish max WOT
Staging Lane
Joined: Dec 2007
Posts: 88
Likes: 0
From: Bethlehem, PA
I've had low oil pressure since I bought my 97 SS. Car had signs of being raced before. The oil pressure at idle was just over 10lbs. I just removed the engine this week and tore it done. First thing that I noticed was the cam bearings where worn down to the copper. They where junk. Removed the bearing caps from the rods and mains and they where in great shape. Just normal wear. Still need to measure the crank to see if its in specs.
