What oil pump are you using and how old is it? I didnt see you mention that.

 

Same problem. 1998 LS1. 50 psi at idle when cold. 12 when hot. Up to 25 psi at 2000 rpm or more when hot. On my second "O" ring. No change. New Moroso oil pump. Around 500 HP. Cam work, head work ... Stumped. I think I'll pin it until it blows up. Then I'll pull it again. Unless someone has any other ideas?

 

Seems for every low oil pressure issue posted, the answers are all unanimously pointing toward the oil pump O ring. While in some instances, this is the culprit... it is not always the cause... or the fix.

Also, while changing oil weight/viscosity will more often than not change oil pressure readings, this is not always the fix either... bearing clearances, operating temps/vehicle use use will determine weight/viscosity.

There is no reason an OEM bearing clearance in an otherwise healthy motor should need more than a 10w oil. Pressure may go up, but at the expense of the bearing.

I'll throw some dumb questions out there.... what oil filters are you guys using, has anyone actually cut one open to have a look?(a twisted/collapsed filter media will play hell with psi)... and those using HV pumps, what pans are you using?

Not all filters are created equal. Several filters are made by the same manufacturer and then private labeled for the various brands, so for instance if you buy x brand thinking you're getting a better product than xx brand, you're really getting xx filter with brand x's label.

There are 3 filter manufacturers that make ALL the filters for ALL the brandings.

For the tech geeks who are curious... see links below;

http://people.msoe.edu/~yoderw/oilfi...lterstudy.html

Condensed version;
http://people.msoe.edu/~yoderw/oilfi...ilfilters.html

A dense media(high micron spec)is not able to flow the oil volumes that a high volume pump produces, hence the lower psi readings. You also need to use the correct filter for your application... a street motor does not need a race filter and a race motor should not be using a street car filter.

As an example.... there are a lot of folks who swear by brand x for no other reason than their Pops or buddy runs it.

FWIW to the OP.... I have removed name brand filters for another brand and picked up 10 psi across the board... cold idle/hot idle and hot under load... using the SAME brand/weight oil.

For the guys in warmer climates.... obviously at hotter oil temps, the oil is going to thin and show lower psi., hence the 60 cold 30(or less)hot. The fix is not heavier oil... the fix is a decent oil cooler.

For the guys running a HV pump and stock pan... are sure you're not sucking the pan dry?

Just throwing out some food for thought.... hope this helps-

 

^^Yep, I know everytime when I'm getting close to a oil change without even relyin on my little dash indicator just by oil pressure. I have always ran Castrol GTX 10w30 year round with a Puralator filter. When I start seeing my oil pressure not where its supposed to be I know its time. So far everytime I have noticed this & changed my oil/filter its cured itself.

 

So a question for the guy at vengeance....

I am running a melling HV pump with stock pan, on cold starts its above 40 psi, after driving normal and warmed up it idles just below 40psi and then after a hard pull it drops to almost 20psi at idle. You mentioned sucking the pan dry however under WOT the psi climbs steadily, the only issue is at idle and i dont see sucking the pan dry while just idling. I run an ac delco filter and penzoil platinum 10w-30 synthetic. I'm really lost at this point of what the problem would really be. This issue is so hard to pin point its extremely frustrating, do you have any advice for me?

 

Well Brown you know LGM built my 402 and she's doing ok. But after a few emails voicing my concerns about low oil pressure at start up during the colder months (early spring / late fall) even while running Mobil 1 15w50 as directed by LGM I drained the thick stuff and ran 5w30 which immediately solved the cold month low oil psi. Now that temps are 80's plus and my oil is due for a change I'm going to go back to 6.5 qts of mobil 1 15w50. Currently has 5 qts 5w30 and 1 1/2 qts of 15w50 mobil 1. With higher summer temps after some very spirited driving and as the oil reaches 209 and above idle psi is as low as 29 lbs and low rpm cruising is only 30 ish until the oil cooler brings that temp under 200*. In these hot months the thicker oil should offer better protection shouldn't it? BTW I always run a Mobil 1 extended life oil filter.

 

why are you mixing oil weights? thats a big no-no

 

Well I had 2 qts of the 15w50 stuff left over so I figured it couldn't hurt.

Do you have some concrete evidence to back up your statement?

5 qts 5w30 mobil 1 and 1 1/2 qts 15w50 mobil 1 makes what? 7w35 LOL.

Very interested to see some info for your statement.

 

I would try this first. I was having the same issue and it turned out to be the oil sending unit after putting a mechanical gauge on it to get the correct reading.

 

i dont have any on my computer, but from what i learned at school, basically the heavier oil creates thick spots in a sense in the oil and can cause differences in the oil cusion that seperates the crank from the bearings oirr cam from the bearings...ect.

 

Doug.... not if the thicker weight was not a consideration when determining/setting bearing clearances(actually the other way around)it takes more psi to move a denser fluid/more volume than does a lighter fluid/less volume.... hence why I asked what filters guys were using, as the higher micron media would need more psi to move more volume as is the case with the high volume pumps.

Also, while the heavier weights/viscosity's will "work" in the colder climates like yours, the lighter oil will make a difference during those months. You're generally not seeing the high temps in those seasons, hence no thinning/psi drops are occurring.

I don't think your example is to the extreme that the OP had described, but thanx for playing

 

sorry to be a bother im going to repost this in case you missed this as I believe you may be able to narrow down my problem.

So a question for the guy at vengeance....

I am running a melling HV pump with stock pan, on cold starts its above 40 psi, after driving normal and warmed up it idles just below 40psi and then after a hard pull it drops to almost 20psi at idle. You mentioned sucking the pan dry however under WOT the psi climbs steadily, the only issue is at idle and i dont see sucking the pan dry while just idling. I run an ac delco filter and penzoil platinum 10w-30 synthetic. I'm really lost at this point of what the problem would really be. This issue is so hard to pin point its extremely frustrating, do you have any advice for me?

 

Yeah.... it's frustrating...

Sucking the pan dry would not be an issue at idle... as much at higher rpm.

As mentioned earlier, it is quite possible that the O ring was nicked/rolled during install, and can definitely be the cause, showing itself at higher operating temps as the oil thins...

I don't "think" your problem is an O ring as your 30-35psi hot idle is fine... 20 psi hot idle after a pull is a little low, leading me to sway toward high oil temps thinning the oil.

I like to see no more than 30* hotter than the coolant temps.

Do you have an oil temp gauge to verify?
Do you have a "good" oil cooler on the car?

As mentioned by 01ssreda4... try a mechanical gauge and see if there is variance between the two. The stock gauges are notorious for being inaccurate.

Bearing clearances grow with mileage/wear.
How many miles on the motor?

 

Thanks Brown !!! The only thing I know for sure was that with 15w50 in the motor during cool/cold spring startups caused the low oil pressure warning to come on for about 5 seconds. As soon as I switched to all 5w30 mobil 1 the problem was gone.

Hope to see your old *** soon bro !!! Hows that Nitrous swilling monster of yours coming? Chassis work and suspension done yet?

Sorry for the slight hi jack.

 

I just swapped the 6.0 into the car and got it running about a month ago. When i first started the car up after getting it back together it would be just above 60psi never got to drive it however due to trans issues. The motor has 72k miles on it, heads have about 110k brand new melling HV pump and custom grind cam. I havent used a mechanical gauge yet nor have i added an oil cooler. I drove the car today and since i have a th400 at 55 im at 3k rpm i was hitting 50psi. Come to a stop and idling around 30psi and didnt drop below that. Its only after a hard pull it drops to 20psi.

 

I had a guy tell me that the problem may be with the oil return. That the pump is shoving all the oil to the top of the motor and the return is partially blocked or for some other reason not letting the oil return to the bottom of the motor fast enough. That is why letting it sit for 20 minutes brings the pressure back up. It is not giving it enough time to cool down but is letting it return. Also when my pressure drops blipping the throttle does not make the pressure spike a little either. When I tore my motor apart for the mods there was an over abundance of varnish on everything. I had to soak my rockers in brake cleaner and then use a dremel on them to get it off. I bought the car used so I don't know what abuse caused this but maybe the return is a little blocked.

 

Update on my own personal oil pressure experience.

With Mobil 1 5w30 and 1 1/2 qts of Mobil 1 15w50 cold start up was 48-50 psi
Operating temps 160-180 (oil cooler works almost too good for reg driving) Low 40's except at WOT and then she goes up nicely into the 60's.
Oil temps 199 to 209 idle psi drops to 30-31, above 209 she will see 28-29 at idle, cruising is fine 39 psi in 6th gear turning 1500 rpms roughly. WOT after dropping down 2 gears she shoots up in the mid / upper 50's.

Now with the 6 1/2 qts fresh Mobil 1 15w50 and mobil 1 filter I started her up and only had 44 psi at idle but oil temp due to hot block was in the 150 range, so was expected. Took her out last night beat the crap out of her (and shocked a new zr1) got the oil temp up to 223 degrees, oil pressure was about 5 psi higher then with the thinner stuff. Let her set over night, started her up and oil temp was still 88 degrees. 48, 49, and then held at 50 psi. Had very little traffic and got to work quickly. 6th gear 125 or higher the whole drive until a TBSS with some mods wanted to play. Dropped to 4th stood on it until the shift light, then ran 5th up to 180 something. Guess his 100 shot wasn't enough LOL. Anyways I pull into my parking area and let the car set. Oil temp is again 223 or so. Idle oil psi wouldve been 27 lbs, maybe less. The thicker oil stands up a lot better to heat and idle psi was 35.

Like Brown from Vengeance said and engines tolerances have a lot to do with oil selection but the builders of my motor LGM, said run 15w50 mobil 1. I will do that as instructed but only in the warm months of summer. If I try to run it in the cooler spring months of March or cooler fall months like late october then I get the scary as hell low oil pressure warning.

Sorry for the long write up just wanted to share my findings. To the best of my knowledge my engine was built by lgm with the intent and clearances for Mobil 1 15w50. Just don't think they took into account that thick oil won't flow in 30 degree weather after sitting in the pan overnight.

 

Not trying to hijack the thread but I have had very simular problems with my motor as of lately. About a year ago I was headed back to my house on I-95 and the passenger side head gasket let go as soon as it happened the car fell on its face and I looked at the temp gauge 180ish so it wasnt because it was hot ended up being a 25cent electical spade that conected my MSD fuel pump voltage booster to the alternator, the wires going into were mostly broken where it crimps only three or four were still conected. So I spent a good 100 miles getting to know a tow truck driver. Thank god for AAA. So while I had the top end off I had some head work done. I also took the time to wrap my longtubes since I have a remote mount and the rest of the exhaust in header wrap. Put the car back together and cranked it up and it seemed good until I let her warm up oil pressure was low as hell just above the 20# mark, and that was without beating on it Cold start was 40# I use valvoline VR1 Racing 20-50 in the summer and 10W-40W in the winter with Mobil 1 oil filter for anyone wanting to know, the car also has a ported LS6 pump.

So after bangin my head against a wall I assumed that the oil temp was getting to hot since I was no longer allowing the heat generated in the heads to escape since I insulated the headers so I was heating up the oil that was on the top end of the motor. To fix this I ordered the ligenfelter oil cooler adapter Part # L300025297 its 99.95 plus shipping (http://www.lingenfelter.com) This adapter has plenty of ports for accessories like an oil temp gauge, supercharger/or Turbo in my case and a line for a mechanical pressure gauge in addition to the oil cooler lines. I bought a fluidine oil cooler off of ebay for like 80ish and I had Napa put together some 10an lines mine were 45 inches to locate the oil cooler in front of the radiator. I still need to buy a oil temp gauge so I can get more data. The car runs hotter now too, I have a 160 thermostat in it and it wont drop below 200F even when it was cooler in the spring so next is a better radiator.

So after installing the oil cooler I start it up and cold oil press is 40lbs per the factory gauge and it drops to 30lbs when hot without beating it, now when I beat on it it drops to like 25lbs that was as of a few hours ago it was 95 degrees out, but if I keep my foot out of it, eventually it returns. To the 30s. I am still not happy with the pressure I am seeing so I replaced the oil sending unit since the gauge has been twitchy. According to the factory gauge oil pressure wont go above 40 when hot even when I stab the throttle. The indash gauge is still the same after I replaced the sending unit. So I go back and pick up a mechanical gauge and install it. I start the car coldish the indash gauge reads 35# the mechanical gauge reads 42lbs at idle I take the engine up to 3K rpm the factory gauge reads 38lbs the mechanical says 60lbs. The factory gauge is off in my car by 5-30lbs depending on were the tachometer is cold or hot.

Just thought I would throw in my own personal experience with oil pressure issues. In my search for knowlege I stumpled across a really helpful web site. www.bobistheoilguy.com If you want to see how your filter and oil stack up against the competition check out this site it is full of independent reviews of all the different major brand oils, filters, additives, ect.. I wish you luck on figuring your issue and sorry about the length of the post.

 

But somewhat of the same issues everyones having...sort of

Had my 6.0 iron block checked but a rep. Shop that all my friends have gone to he also balanced my assembly for my 403ci. He checked the bearings on main and rods for me and said I'm all set just has to be put together so me n my buddy put it together and he's built motors so this isn't our first rodeo.

Get the motor in the car using 10/30 oil and pressure is a notch about 60psi on dash car idles to running temp ~185* still at above 60psi drive to the highway good pressure still do a pull 50-100 oil press goes to about 40psi now sit at the light about to go back on highway now its down to 20psi and car is running like crap because the lifters are bleeding down and have no oil to keep them pumped up and you can hear the lifters clacking. That was with 10/30 so lifters are new switched to 20/50 still same exact problem happened same area off highway..oil pump is tsp ported ran fine off my 347 went straight into a clean zip loc bag off the other motor. Now go home shut off the car for 10 to 15mins start it noise starts then its gone with good oil pressure.

So possiblities I think .....oil pump o ring/oil pump spring like bypass stuck open when hot/rear main seal leaking down/cam plate not sealed/need new barbell plug...

*all plugs are in so its either leaking oil somewhere in the block or the clearences are to big they are at about .003 to .0035 I believe I don't have the sheet in front of me so don't quote that yet

Any suggestions or help would be great I know this has been around on here for a while and there have been other threads.

 

^^^^^ to the above poster

Dumb question but if the rear main seal is leaking slightly it can cause this much of pressure drop?