oil pressure problem

**DADCRUISER** · 02-16-2014, 07:13 AM

i have 98trans am conv. it has 254000 milesdoes not burn oil or leak,use syn oil an restore every 4000 miles. car was leaking oil, mechanic said it was gasket around oil filter an fixed problem. every since oil pressure has drop 10psi,40 cold,18 hot. it doesn't fluctuate +/- 2psi at any speed. mechanic checked presure relief,sensor and op gauge all ok. going to pull oil filter and check for shavings in pleats. after that i'm not sure what to do next. any sugestions? other than this engines runs and sounds normal. no lost of power or fuel milage.

***SMWS6TA*** · 02-16-2014, 11:06 AM

Pull the filter first and check it. If no metal shavings next pull the OPSU that is just behind the intake on the drivers side. Parts stores do sell a socket for $10 (worth it). It can be done without removing the intake, just tight.

The OPSU can fail, crack or just quit. Inspect it. See if the diaphragm is still intact, no cracks and moves freely when pressed on.

Report back what you fine.

How long since the OPSU was replaced?

What weight oil are you using?

Correct oil filter use?

**DADCRUISER** · 02-16-2014, 11:42 AM

thanks will do. using 5w-30 synthetic with restore. oil filter is same one been using for years. oil pressure unit replaced 10,500 miles ago [243621 NEW VALLEY PAN,INTAKE MANIFOLD KIT,INJECTOR O RINGS, OIL PRESS.SW.,SPARK PLUG WIRES[LIFE GUAR]

***SMWS6TA*** · 02-16-2014, 01:10 PM

well if it's not the opsu next thing to check will be the oil pump and pick up tube o ring. if never replaced based on the mileage it may be time for a new one.

Melling 10295 is a perfect pump if you need one.

***SMWS6TA*** · 02-16-2014, 01:36 PM

also OP I had your thread moved to the General Help section so that others can view it better.

**2002ssslp** · 02-16-2014, 03:21 PM

With 254k on the clock it could be anything but I would start out with the simple things like the oil filter, OPSU, the gauges are not accurate so don't trust them. Pull the OPSU and hook up a mechanical gauge for an accurate reading. After that you may be looking at internal issues like bearings or the oil pump. 254k is a good run for any motor so if it is internal you can't say it was unexpected. Good luck.

***SMWS6TA*** · 02-16-2014, 03:50 PM

98's have true gauges. Only yr to have them.

**DADCRUISER** · 02-17-2014, 06:51 AM

thanks for the responses. did mechanical guage thing. changed oil pan gasket 5k ago,oil pan,oil breather tube assembly 12k ago. mechanic did not indicate any problems. I assumed oil pumps just quit not just die slowly. sunday will pull oil filter and check for shavings,check OPSU. any suggestions on oil weight to delay the inevitable if i find shavings.

**kingls1** · 02-17-2014, 08:42 AM

What oil filter are you useing? I have been told that Fram filters have been known to collapse on the inside due to poor material used internally. I would think that could cause pressure problems. I've been using a K&N filter costs a little more but I love the nut on the bottom for removal.

**Guerrillakilla13** · 02-17-2014, 12:21 PM

wow 254k miles? That makes me feel better about my car and the possible longevity of it

Did you see any shavings? How's your OPSU?

**2002ssslp** · 02-17-2014, 03:11 PM

Originally Posted by kingls1

What oil filter are you useing? I have been told that Fram filters have been known to collapse on the inside due to poor material used internally. I would think that could cause pressure problems. I've been using a K&N filter costs a little more but I love the nut on the bottom for removal.

K&N is the only oil filter I use.

**Guerrillakilla13** · 02-17-2014, 03:28 PM

Really? I heard fram was a good one. And so long as you change your filters every oil change you should be alright..

Still, no more Fram for me!

**35th-ANV-SS** · 02-17-2014, 05:41 PM

Fram is a good filter now - it wasn't in the past. The design has changed.

**Firebirdjones** · 02-18-2014, 04:14 AM

If you use the Fram extended Guard XG filters in the gold and black boxes, they are excellent filters. It's the same filter now as the Napa Gold, or the Wix,,,,all of which are excellent filters and still a reasonable price compared to Mobil or K&N, which in various studies show them to not be any better at filtration.

I doubt it's a filter issue Dadcruiser. If you have verified oil pressure mechanically that would rule out any sending unit or gauge problems. You have something internal going on for sure. Whether that's an 0-ring on the pickup or a bearing failure it remains to be seen. Best thing you could do is remove the filter and cut it open to check for debri, and also possibly send a sample off to Blackstone to see what might be in there.

If that comes back clean, it might not be too late, and I'd check the 0-ring and hope that's it.

**DADCRUISER** · 02-18-2014, 06:03 AM

WHAT IS BLACKSTONE? I appreciate the info on filters. if they find shavings this sunday I'll plan to go to a higher,10w-30, oil until I fix the engine. would higher be better?

**Firebirdjones** · 02-18-2014, 08:37 AM

Blackstone is an oil annalys that breaks it down with a wealth of information. Things like how much life is left which gives you a good idea on change intervals, whether or not your air filter is doing it's job, whether your oil filter is doing it's job etc... If there is something in the oil that doesn't belong, they'll tell you exactly what it is and how much, and you'll have a pretty good idea where it came from and what you can do filtration wise and oil wise to combat it. Just mail in a small sample, doesn't cost much. It's a good overall indication of just how healthy the engine is and whether or not your choice of oils and filters are working for you.

If you find shavings in your filter, a thicker oil won't help. Damage is done. Trying to drive it would just do further damage and make the repair even more costly.

**cammed goat** · 02-18-2014, 10:27 AM

I was also about to ask what oil filter was being used as I despise the E-core(plastic cage) inside. Yuck!

**Firebirdjones** · 02-18-2014, 10:32 AM

I believe the AC Delco filters are of that E-core design you mentioned. I would have expected better from GM. The Ford OEM Motorcraft filters are excellent quality and according to the charts, they filter right up there with Wix, Napa Gold, etc.... The AC Delco is Waaaaay down the list, lol.

**cammed goat** · 02-18-2014, 10:44 AM

I use Purolator. I even open the box and look down the filter opening before I buy to see if there is a black plastic cage inside. If I see a black plastic cage, the filter goes back on the shelf.

***SMWS6TA*** · 02-18-2014, 10:46 AM

Originally Posted by DADCRUISER

WHAT IS BLACKSTONE? I appreciate the info on filters. if they find shavings this sunday I'll plan to go to a higher,10w-30, oil until I fix the engine. would higher be better?

DO NOT RUN THE ENGINE AGAIN TILL YOU KNOW IF YOU HAVE debris in the oil.

Hear my tale and heed warning.......

I over rev mine NOV 2012 and bounced off the rev limiter twice on a burn out. Thought I was ok, next morning went on an errand and it got worse. Thought at first it was a bent push rod or stuck lifter because my oil pressure read normal. Pulled the heads and found #4 intake valve had floated. Replaced the lifters & push rods anyways. Got it back together and and did a couple of test drive, on the second test drive it just let go.

I limped it back home. Few weeks later pulled the motor and began tear down. It turned into a horror show.

In the end #3,6,7,8 rod bearings spun, #3, 4, 5 main bearings spun. Destroyed the crank, #7 & 8 pistons cracked on the underside of the piston and cracked the block internally.

SO WHEN WE SAY DO NOT RUN IT this is why.

If you click on my 6liter build link in my signature you can see all.

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