jgstang

I'm having oil pressure problems... at idle i'm 36, after warm up if i get to 1800 rpm i will loose pressure down to probably 5. if i let up on the gas it will go back to 35 ish, new oil change with 10-30, put some lucas stableizer in and it seemed to help just alittle. i replaced the pressure valve also.. maybe the the hole at the valve is plugged slightly ? i have 175,000 on it and it just started doing this. motor sounds clean with no knocking, before the lucas it went to like 5 lbs while driving and i pulled over and did here clicking from a couple lifters so i turned it off. started it and drove home 2 miles. right now if i run it in park at 1800 rpm it will drop, if i bring it down to 1200 rpm it gos back to 36 ? no bad idle or anything, runs strong and smooth.. thanks

jgstang

Just took it for a 20 mile drive at 60 mph, fine no drops in pressure, 2 miles from home going 55 mph it drops so i slow down to where the tach says 1200 and it shoots up to 36 again. get back to 55 and again so i slow down and this time it does not go back up so i pull over and idle.. stays just above 0 for 2 min but this time the red warning square on the car on the dash starts flashing so i turn it off! turn it right back on and 36 lbs again, no ticking or knocking at all.. so back again to it dropping @ idle 1800 rpm and back to 31 @ 1200 rpm. i guess i'll put on a gauge at the block to see what is happening! if the gauge drops would you think bearings or pump ? i always thought that if the bearings or pump were bad there bad! thanks

97grand4.0

That is very odd, because if the bearings or pump is bad, the pressure drops out at idle, not at some rpm. I suspect a gauge or sender related problem. But you sure want to know for sure and not ruin your mill.

jgstang

I know just because the pressure valve is new doesn't mean its good but with that new, new oil and filter ? put a real gauge on it and see, and if it drops to... oil pump screen ? and if thats clean ? if i had bad bearings would it make noise ? i'll see what a actual gauge says first... thanks

97grand4.0

I guess from your writing and lack of punctuation it's hard for me to tell if you are saying it drops at idle, or at a higher rpm and then recovers at idle.

jgstang

I'm not a writer thats for sure... here is what happens! i let the jeep warm up for 10 min and oil pressure's at 31, get on the road and going 55-60 mph witch is close to 1800 rpm.. all is good, i can go 40 miles or whatever until the motor get just before half which is 200 ish temp wise because its so cool outside. the car is now at normal running temp! if i watch the tach and if it gos higher than 1800 rpm the pressure will drop like it got un-plugged.. at this point i let off the gas and bring the tach down to the 1200 rpm range and the pressure will go right back up to 31 and stay unless i go over 1800 rpms..i have 31 lbs steady at idle period. if i bring the idle up in park to 1800 rpm i will loose the oil pressure right away! as i'm watching the needle drop i also bring the rpms down to 1200 and the pressure recovers right back to 31. i just went to town to get a gauge which is 14 miles up/down hills in a canyon and its hard to keep it under 1800 rpm with the damn trans shifting with the hills but i did for the most part! it only dropped once going up the hill under load, i let up off the gas for a sec and it recovered.. so to make this clear from my stand point, in park in the driveway if i bring the idle up to 1800 after completely warmed up it will drop like its un plugged, i will bring the idle down to 1200 and it will recover and stay good as long the motor is below 1800! i hope this sounds better.. thanks

jgstang

By the way, thanks all for your time...

jgstang

ok so i put a machanical gauge on today and here is what happend... start up from cold 45psi, then gos down as it warms to about 38psi.. take it for a drive and after warned to normal temp @ 55-60mph around 20psi. if i climb up and hills it gos to around 15psi and when i get on flat hwy gos up to 20psi. the lowest it got was coming up my steep driveway was 11psi then in park idling 20. so what now ? thanks

peep

Those readings are not good and are backing up your dash gauge.
Prior to your mechanical readings it sounded like a loose connection to sensor swithc, bad sensor switch, or bad ground on the gauge/gauge cluster could cause up and down readings.

For a cheap attempt, swap your oil filter, and top up your oil level.

Since no knocking, the bearings are sounding ok.

I'm suspect of the oil pickup and tube on the oil pump (fallen off or loose) since the pressure seems hill affected, but I don't have any viable background on the 5.2L motor. Perhaps someone with 5.2L experience could provide info if this is possible.

Even warm a good condition engine will have about 40+psi at idle, 50+psi at steady cruise.
Even old oil at warm should have 30+psi at idle.

Those low low readings running and driving should be taking out the main bearings. There should be developing noises.
I know you tried a mechanical gauge. Do you have any buddies or a mechanical shop that can run an additional gauge test?

Sorry, no good news.

jgstang

I hear a clicking now, not a lifter or exhaust on start up... almost like a something is just barley hitting as it is going around and is kinda loud at first, then as it warms it gets lighter and lighter then it gos away! well today about 9am i started it up and pressure only @ 5 , turned it off after 45 sec. started it back up and the same so turned it off, 2 min later turned it back on and it started climbing slowly and went to 25psi. went to town and not good, i ended up pulling over 1 mile from home when it went down to like 2psi and i heard it ticking and shuter down.. let it sit for 5 min started it and i had 10 so i got home went up the drive and it dove to 1 or 2 ! let it sit for 1.5 hrs and started it and 50psi then 45, went to the store and went to 20 and then 14, got to my drive again and dropped to 3 turned it off. for some reason 1800 rpm is a magic # , because when i go above that it drops down now, let up and go below and it comes back up but not as high.. as the motor warms it has a harder time recovering for sure! so i will change the filter just to see then the oil pump.. that noise i heard sounds like a bolt hitting the flywheel real steady but then fades away after 10-15 min.. If the bearings wear bad would i hear any noise ? the motor runs smooth, lots of power and runs cool. thanks

97grand4.0

Barley hitting? Something to do with beer brewing?

jgstang

Well same o'l crapola.. So took a ride into town to talk to napa auto parts machine shop! this guy has been there over 20 years and here his input.. if i had bad bearings they are bad bearings and will not give me all differant readings. he said its a slim chance the oil pump is bad... don't know about that one! he says to check the oil pick up and i could try motor flush, but if i do that i might have some oil leaks that i didn't before.. i got a 16.00 K&N filter for it, but i think i'm going to drop that damn pan to see what the hell is going on and just replace the pump and get it over with and clean or replace the pick up screen.. only differance today was coming home up the drive i stayed @ 1100 rpm and the psi stayed @ 18 what i don't understand is first start up in the morning i get zero after 30 sec so i turn it off and restart and it gos to 45-50 until i start driving it.and if it gos down to 5 psi and i turn it off and wait 30 sec and start i have 40 psi until driving again.. I guess i will find out!

jgstang

ok done.. new replacement oil pump and k&n filter. now at start up cold i have 65 psi, drive it and get it warm to normal running temp and i have 60 psi driving, let it idle and 38 psi.. take off and back to 60. how would i know if the bearings got messed up ? thanks

peep

Looks like the oil pump was the failing component. The bearings probably didn't come thru fully unscathed. However you have currently, excellent pressure values. Warmed up and at 38 psi is fine, good even! If the bearings were pooched you would have significant rattles/knocks and continue to have poor pressure when warmed up as the engine expansion has the widest clearances once hot.
Keep up regular oil changes (6000mi - 10000km Max) with a new filter every time.
Your pressures may drop 5 psi as the pump "breaks in" and ages. If things return to your prior low pressure conditions, that would be the biggest indicator that bearings have worn out.
In the interim, sounds like you found the fix. Safe travels!
A ford FL-1A, or DL8A filter is longer than the stock filter body and can add almost a half litre more oil than the stock filter. Works great for the 4.0L engine. Before you change out on the 5.2L make sure you have clearance for movement of the upper control arm. If too tight, stick with the stock filter.

peep

It's been a week.
Is your oil pressure still strong?