need engine guru advise.....high oil psi

[Old Guy with 87 GT]

my oil pressure has been goofy within the last couple of days .......figuered i'd see what you guy's could make of it

the specifics::::last week i noticed my oil pressure wasn't fluctuating like it normaly does.......was stuck at a lower pressure:like 20-30 psi.......when i took it for a good size drive and wound it up a litte the pressure went up to around 45-55 psi and stayed there........it's been staying around 50 psi ever since then............i checked the guege so it's not that(changed sending unit and varified with after market gauge)......i changed the oil filter so it's not that

this has me puzzled......the pressure is the same whether i'm taching 5,000 or at idle,whether it's cold or warm........it fluctuates a little (like from 45 to 50,55 psi) but not as much as usuall,before it would fluctuate from 10 psi to 75-80 psi depending on rpm and temp......now it just seems like the guage is stuck(even the aftermarket gauge)......the engines not runing real hot and doesn't seem to be making any funny noises.........

i'm concearned becouse the sudden change might suggest some internal problems........i just don't know what would cause it......the pump works becouse it has pressure but why isn't it dropping at idle or when the moters warm...............any insights would be appreciated .....thanks

[Coupe Devil]

How many miles? I assume you change the oil every three thousand as well. My first thought would be oil valleys in the heads and lifter valley but I'm not sure. Just my OPINION, you should probably wait for someone else like PKRWUD to reply.
Maybe this wil help though

Brad

[Old Guy with 87 GT]

i change the oil pretty religoisly......usually every 2-3000 miles......i only changed the filter becouse the oil only has like 800 miles on it ,it still looks pretty clean.....i changed the filter cause i was thinking maybe it caused the problem .....but there was no difference after filter change

[Old Guy with 87 GT]

oil valley's???? ......somone eles said there might be back pressure from somwhere .......i'm still puzzled and concearned.........any advise is appreciated

[PKRWUD]

This condition has been verified with a mechanical oil pressure gauge?

[Old Guy with 87 GT]

i did hook up a mechanical gauge .....it seems to read close to what the dash gauge does......the dash gauge works but does'nt seem as acurate ,according to both gauges , it's staying around 50 psi......

[Unit 5302]

Well, low oil pressure when the engine warms up is generally a symptom of bearing wear.

What your oil pressure is doing now is what it's supposed to do. The serious fluctuations in the pressure and strange behavior makes me suspect your oil pump. Check your oil for metal to make sure the shaft isn't wearing.

[PKRWUD]

Your oil pressure is not doing what it's supposed to. If you are certain your measurements are correct, then the only possibility is the oil pump bypass valve is stuck closed, or partially closed. Driving with it like this can be dangerous, and is not advised. Possible results include a ruptured oil filter, popped out oil galley plugs, a damaged pump and bearings. More than likely, pieces from your valve stem seals or RTV that has come loose has jammed the pressure relief valve.

Take care,
-Chris

[1965GTO]

Ok here it is straight from the Motors auto repair manual troubleshooting section. High oil pressure: 1. oil pressure guage defective 2.oil too heavy 3.oil pressure relief valve adjustment too heavy 4. relief valve spring too stiff 5. oil presure relief passage clogged 6. plunger type relief valve stuck by gummy oil or plunger is too tight a fit 7.main oil passages on pressure side of pump clogged Looks like the most likely culprit is the relief valve.

[onefastlx420]

hey i was just wondering my oil pressure has been acting up, at idle the pressure is fine but when accelerating the pressure drops any ideas? the temp is fine and i have no noise from the engine besides the usual rocker clatter

[Old Guy with 87 GT]

sounds like you guy's are probly right......i did my waterpump and timing chain recently so it's intirly possable that a foriegn object might have gotten into the oil system......bummer

i was planning on rebuilding the bottem end when i got my tax return (180,000 mileson it )......so i guess i'll just tear it down a little earlier.......

onefastlx 420......not sure what would cause your delema......when you excellerate does it drop momentaryly or does the pressure stay low .........whats it do when at a higher rpm held evenly

[richd]

Hmmm...my pressure guage has been doing the same thing. I haven't yet verified this with a mechanical guage.

Also, when I did an oil/filter change (5 qts) I wind up with too much oil according to the dipstick. I did change the oil when the engine was completely cold, so maybe there was some old oil left over.

I'm going to watch the guage tonight and let you know exactly how it behaves.

Any suggestions until then?

Thanks,

Rich D.
89 LX50 (stock)

[Unit 5302]

I wasn't aware 50psi would blow anything up. If it's hangin out at 50psi, and it's not exceeding any safety factors, or anywhere near safety factors for that matter.

His oil pressure certainly shouldn't be less than 30psi at idle, it should be around 40psi with the system functioning properly. I'm not aware of a variable rate bypass on the oil pump, so 50psi just indicates pressure being a little high, not anywhere near blowing stuff up.

[PKRWUD]

Originally posted by Unit 5302
I'm not aware of a variable rate bypass on the oil pump, so 50psi just indicates pressure being a little high, not anywhere near blowing stuff up.

What do you think the spring is?

He is most definately running a high risk driving it the way it is. I guess you've never seen this before, which is cool. Once you do, you'll never forget it. Anyway, if his relief valve is sticking, it will lock up before it will free flow, and if it locks up closed (they usually do), his pressure will exceed 50 psi.

Take care,
-Chris

[Unit 5302]

PKRWUD, a stock 5.0 can certainly produce 50psi. I realize there is a pressure safety valve, but it's set at a fixed pressure, not variable depending on rpm. It may be the case that his valve is stuck, but I have extreme doubts the factory oil pump has a prayer in hell of exceeding safety factors for the oil filter. How about the older 427 FE's? They featured very powerful oil pumps, with NO bypass in them. The bypass was in the block, set at 125psi. Running cold they could barely exceed 100psi. When warm, they made 60-80psi. The oil pressure rises with RPM. It doesn't stay constant, especially in an old engine with 170,000 miles of bearing wear.

It certainly could be possible that his valve is stuck, but if the result of that is 50psi of pressure at idle, I need to wedge mine shut as well.