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.

[PKRWUD]

Unit-
Just because you haven't seen it doesn't mean it's unusual. I'm very surprised you haven't dealt with it before. I'm also surprised that you are so adamant about being wrong. I'm not trying to win a prize, I'm trying to help others with what I know. You act like I don't have a clue about what I'm talking about, and I'm getting kinda tired of it. We've "known" each other online for 3 years, and it's always been cool, but since about Thanksgiving, you've become a total stranger. That's too bad. Anyway, below is a clipping on oil pump relief valves from Automotive Engine Rebuilding, by James G Hughes (page 481).

[Old Guy with 87 GT]

interesting debate.......i took the stang out yesterday,kept a sharp eye on the pressure .......still keeping it's pressure at around 50psi ,i did notice it it fluctuated a little bit more after driving it a while (hot engine).....it was going between 40psi at hot idle to 55psi at high rpm .........i still think somthings not right ,before it would fluctuate alot more .......
intill i hooked up mechanical gauge i didn't have anything to varify dash gauge ......although the dash gauge is not as fast, it still works.....according to the dash gauge ,before the condition started it would peak around 65-70-psi and drop to around 20 psi..........i won't know for sure whats wrong till i tear it apart .....

i'll keep you guy's updated.....i just got my w-2 so when i get tax money i plan on disecting the moter anyway.......

i'll probly take it out to play tonight for one last time then park it and start tearing it down.......i figuer if it has pressure then it isn't hurting the vitals of the moter......then as long as i don't go on any long trips i'll be allright ........if somthings blows i'll just tow it home ......i probly put like a 100 miles on it yesterday and it wasn't making noises,running hot or getting worse .........

my main concern was the vital parts of the moter.......ie distributer ,crank,valves,heads, cam.......i appreciate the advise and help and i'll probly have some more questions in the near future......i want to tear down moter before i make any solid plans on what to build ,but i know i'll have combo questions when i do

well thanks .........................james

[PKRWUD]

Tearing it down is the only way to know for sure. I'm never 100% on anything I haven't seen with my own eyes, but based on everything you've said, it looks to me like your bypass is not opening fully. If what ever is obstructing it gets worse, damage will occur. My only debate was whether or not a plugged bypass could cause an oil filter to blow (I've seen several of them, and it's not pretty!). I think everyone would agree that when an engine with 170k miles has a sudden, unexplained jump in oil pressure, something is wrong. I think it's just difficult for some people to accept an idea that they aren't familliar with (I know I used to be like that). It just disturbs me when they get so high and mighty about it. Oh well.

Good luck!

Take care,
-Chris

[Unit 5302]

Quite frankly, PKRWUD you're the one perceiving the attitude here. I'm just entering another viewpoint into the conversation. He was running more psi before the bypass valve "stuck partially closed." He was also running less at idle.

Old pressure 20psi@idle 60-70psi@higher revs
New pressure 50psi@idle 50psi@higher revs.

While the pump in a race car, or car that generates higher oil pressure than a Mustang 5.0 may be capable of blowing an oil filter up (I've seen this as well), the stock Mustang oil pump isn't capable of generating that much pressure to blow the oil filter. 100+psi.

I would expect pressure to continue fluctuating if his relief valve was partially clogged. As the rpms increase, I would expect the oil pressure to increase as well. 40psi@idle 60psi@higher revs is what I would expect for a really good working stock 5.0 oil system. I do agree with you that something has changed, and the oil pump could certainly be at fault, but the linear diagnosis doesn't seem accurate.

I would be more inclined to believe that the valve was stuck before now. That his long drive heated the oil up, and discharged the debris. If it was stuck slightly open it would generate crap pressure at idle, and very high pressure under higher rpm running. Exactly what he was describing. As of right now, it's performing the way I would expect a very nice system to be working. Perhaps the valve is now functioning properly?

Anyway, I'm no stranger to anybody on this board. Sorry to hear you think that I've somehow become one?

Later,

Kell

[PKRWUD]

I guess we'll just have to agree to disagree.

Take care,
-Chris