is oil pressure ok??

Hi, I have a 96 cherokee 4.0 Hi-output 4 WD with 167000 miles. When I start the Jeep it has about 65-70 psi oil pressure. After driving a bit, the pressure drops to around 50-55 while driving, and 25-35 psi at idle. I just bought this Jeep used and was wondering if this would be the cause of my check engine light to come on as it does. It will be off for a couple of days, then come on for a couple of days. Is there anything I should check before I get into real engine trouble?

Minimum oil pressure spec is 13 psi at 600 RPM. Oil pressure should be 37-75 psi above 1600 RPM. Maximum oil pressure is 75 psi These are the specs from the FSM so looks like your good to go!!!What oil are you using? 10w30 or 5w30???JD

Preciate it. I am using 10-30. This is my second jeep. first was older wihout all the guages. I wasn't sure where I should be, so I appreciate the help.

Hey, can anyone help me? I've got an 87 cherokee with nooo oil pressure sometimes, very little all other times, and normal pressure about twice a week for about 10 minutes each time. I think its the pump, what do you guys think?

Hey, can anyone help me? I've got an 87 cherokee with nooo oil pressure sometimes, very little all other times, and normal pressure about twice a week for about 10 minutes each time. I think its the pump, what do you guys think?


I HAVE THE SAME PROBLEM WITH MY 1987 JEEP CHEERK...I AM GOING TO CHANGE THE OIL PUMP IN THE MORNING...I WILL LET YOU KNOW IF THAT WORKS'........
BARGERUNNER66

Quote: <HR SIZE=1>Originally Posted by cusz28
Hey, can anyone help me? I've got an 87 cherokee with nooo oil pressure sometimes, very little all other times, and normal pressure about twice a week for about 10 minutes each time. I think its the pump, what do you guys think? <HR SIZE=1>

I HAVE THE SAME PROBLEM WITH MY 1987 JEEP CHEERK...I AM GOING TO CHANGE THE OIL PUMP IN THE MORNING...I WILL LET YOU KNOW IF THAT WORKS'........
BARGERUNNER66

I seriously doubt that your problem is in the actual pump. More likely the regulating valve that is in the pump housing. Can stick intermittently. I've had good success with using an engine flush to remove the deposits and have obtained a steady pressure that way.

Could also be a plugged pickup screen. Deposits block flow to pump gears and can be intermittent too. If the flush doesn't help, removing the pan will show this right away.

Others have had success with replacing the pressure sender and/or fixing the connector contact to the wiring harness.

Both easier and less expensive than replacing the pump.

JD

I would question bearing clearance first. The bearings is what makes the oilpressure. Oil pressure comes from how much pressure it takes to send oil down it's ways. When bearing wears the oil pressure will always drop. The more the wear the more the drop. The pressure may increase at higher rpms only because now you are trying to send more oil. If i was going to drop pan to change pump I think I would go ahead and do the bearings. You will thank youself for doing so.

I forgot to include the "always do first thing".

Alway check your actual oil pressure with a mechanical gauge - under normal operating conditions - before going ahead with any work to "fix oil pressure". "You will thank youself for doing so", too.http://www.automotiveforums.com/vbulletin/images/smilies/smile.gifhttp://www.automotiveforums.com/vbulletin/images/smilies/smile.gif

JD

Hey, I have had the same problem with my 98 cherokee. I was told by some guys at the Jiffy Lube where I wash windows (a very lucrative college job :rolleyes: ) Anyways, what happens is when I start it up oil pressure is right on, but as it idles the needle drops. But if I start driving the oil pressure climbs back to normal. One guy told me that it was the fuel pump probably. But the manager of the store told me that it was some sort of ring found where the oil pumps through, and it is much cheaper than the pump and easier to fix. Can't remember exactly what he said. Will ask him again tomorrow at work.

Good Luck on that one. That story told to you won't hold any water. But coming from Jiffy Lube,,,,,?

Okay, i mis heard him. He was talking about some rings found on the pistons. Sometimes one of the rings will go bad which will give off a bad pressure. Also it might be the pump, or many other items. Dont want to figure it out though.

I'm new at the whole jeep thing. but I have been around (and IN engines) enough to know that it isn't a bad oil controll ring or just normal driving, nothing personal sklater, but I will never go to Jiffy because they like screwing stuff up. be glad it's only a collage job... as with the mechanical gauge, it's a good idea, if i had one. as with bearing clearance, my engine can't remember the time when it had .002 clearence on it, it has 234,000 miles. what I'm in dilemma with is the fact that it sometimes jumps to around 40, then drops to zero, then stays at 15 for a long time, then drops to zero. and so forth, but 40 psi comes few and far between, thats what I'm worried about. the engine flush is a good idea, I need a change anyway. Well, if you guys could help me out by throwing some omre ideas around, that would be great. again, I'm no novice at all about engine building, i just don't really deal with 4.0 straight sixes. more like 350's or 400's for me. I know that sixes have a tendency to be a real bitch, so the more ideas the better. ~thx

Hi, I have a 96 cherokee 4.0 Hi-output 4 WD with 167000 miles. When I start the Jeep it has about 65-70 psi oil pressure. After driving a bit, the pressure drops to around 50-55 while driving, and 25-35 psi at idle. I just bought this Jeep used and was wondering if this would be the cause of my check engine light to come on as it does. It will be off for a couple of days, then come on for a couple of days. Is there anything I should check before I get into real engine trouble?

I have had this problem on my 97 Cherokee 4.0L for the last 50k miles on and off. Jeep now has 123K on it, and it has always been the sender.
First change the oil and filter to make sure the oil filter check valve is not stuck open, then change the sender which is easy to get to. You will see at the parts store that Chrysler changed the sender design later.
The weather pack connector on these Jeep gives many electrical problems.

Hi, I have a 96 cherokee 4.0 Hi-output 4 WD with 167000 miles. When I start the Jeep it has about 65-70 psi oil pressure. After driving a bit, the pressure drops to around 50-55 while driving, and 25-35 psi at idle. I just bought this Jeep used and was wondering if this would be the cause of my check engine light to come on as it does. It will be off for a couple of days, then come on for a couple of days. Is there anything I should check before I get into real engine trouble?

On your erractic check engine lite, it could be anything but most likely the NSS switch which can be rebuilt. Pull the code. Many people posting has had this problem.

My problem is similar, lately when I have to stop quickly, the oil pressure drops very low and then recovers quickly, I have also noticed that if the engine starts to get too hot, my oil pressure will also drop. I have an 89 I-6 unfortunately I only have the dummy lights so I cant give exact readings.

My problem is similar, lately when I have to stop quickly, the oil pressure drops very low and then recovers quickly, I have also noticed that if the engine starts to get too hot, my oil pressure will also drop. I have an 89 I-6 unfortunately I only have the dummy lights so I cant give exact readings.

Hey all. Keep in mind a few things...

Oil pressure always drops some hot. Most factory(Warranty) info suggest if you have at least 10 psi at a hot idle, and 30 psi at higher rpms, you won't have a problem. Yes, I also like a lot more, but they are technically correct. Use a manual pressure guage to be sure of the guage accuracy.

I personally don't like engine flush. I've seen it knock loose too much crud at once and wipe out bearings on very dirty engines. I drop the oil and filter, fill 'er up with transmission fluid, (Its basically very high detergent oil) and let it idle for a half hour or so to gently loosen things up. Then a fresh oil and filter change and it's good to go. Been doing this for twenty plus years with out a problem. Lubes while it cleans..


Oil pressure should turn on the check guages light, not the service soon light for emission controls. Sometimes people confuse them and look the wrong direction.

I personally don't like engine flush. I've seen it knock loose too much crud at once and wipe out bearings on very dirty engines. I drop the oil and filter, fill 'er up with transmission fluid, (Its basically very high detergent oil) and let it idle for a half hour or so to gently loosen things up. Then a fresh oil and filter change and it's good to go. Been doing this for twenty plus years with out a problem. Lubes while it cleans..





Hey OlJeepTek,


Wow, you guys sure know alot! I have never heard of that trick before.

What do you think of "MARVEL MYSTERY OIL"? I added some to the Gas Tank and on my next Oil Change I'll add some to the Synthetic Oil.


Thx, Phil

Hey OlJeepTek,


Wow, you guys sure know alot! I have never heard of that trick before.

What do you think of "MARVEL MYSTERY OIL"? I added some to the Gas Tank and on my next Oil Change I'll add some to the Synthetic Oil.


Thx, Phil

I've never been much of a fan of what we called "Potions and Voodoo". (Most highly touted cure-all additives don't usually do much.) I do like some JB and Wynns products.

I've never tried the Mystery Oil in a car, but I use it as an air tool oil religeously. Does wonders for them!

It's been my observation that quality name brand synthetics don't really need any additives

My problem is similar, lately when I have to stop quickly, the oil pressure drops very low and then recovers quickly, I have also noticed that if the engine starts to get too hot, my oil pressure will also drop. I have an 89 I-6 unfortunately I only have the dummy lights so I cant give exact readings.

I have a 91 and when I first fire up, everything is right on. When I am driving around, it is around 20psi.

need to knoe if hot or cold

20 psi hot and at highway speed is a little too low. 20 hot and sitting at idle is just fine.

Hey all. Keep in mind a few things...

Oil pressure always drops some hot. Most factory(Warranty) info suggest if you have at least 10 psi at a hot idle, and 30 psi at higher rpms, you won't have a problem. Yes, I also like a lot more, but they are technically correct. Use a manual pressure guage to be sure of the guage accuracy.

I personally don't like engine flush. I've seen it knock loose too much crud at once and wipe out bearings on very dirty engines. I drop the oil and filter, fill 'er up with transmission fluid, (Its basically very high detergent oil) and let it idle for a half hour or so to gently loosen things up. Then a fresh oil and filter change and it's good to go. Been doing this for twenty plus years with out a problem. Lubes while it cleans..


Oil pressure should turn on the check guages light, not the service soon light for emission controls. Sometimes people confuse them and look the wrong direction.

COuld be as simple as a sending unit - My 93 wrangler had one go bad and it took a 300 dollar oil pump and a weekend of intense labor before finding that out. The oil level would fluctuate wildly, spiking out and bottoming out in a random iterations. I would try replacing the sending unit before spending big bucks on a new oil pump. With that many miles though, it could be a bad pump as well. If the pressure isnt spiking, which it sounds like it isnt, things seem to be normal. If your emissions light is coming on, could be as simple as an O2 sensor...the Wrangler did that as well only it flashed codes at me on the diagnostic...

Hi, I have a 96 cherokee 4.0 Hi-output 4 WD with 167000 miles. When I start the Jeep it has about 65-70 psi oil pressure. After driving a bit, the pressure drops to around 50-55 while driving, and 25-35 psi at idle. I just bought this Jeep used and was wondering if this would be the cause of my check engine light to come on as it does. It will be off for a couple of days, then come on for a couple of days. Is there anything I should check before I get into real engine trouble?
You are o.k. 13 to 75 psi is the spect.it also depends on what oil grade you are using and the climate, but you are good.

Oil pressure is going to be greater during start-up because of the oil's resistance to flow. As the oil warms, it will flow easier, therefore reducing pressure. Once the oil has warmed and stabilized, the pressure becomes a function of RPM. The lower the RPM, the lower the Pressure, just as if the RPM were higher, then pressure will be higher. This is all normal. The erratic pressure readings can be attributed to a bad sending unit. To verify this, connect a secondary gauge to verify proper operation.

I've got an '89 4.0l Selc.4x4 Laredo and my oil pres. guage stays pegged at all times...

I'm thinking the sending unit or the wire(s) on it. Problem is, I can't seem to locate the badboy...

Anybody know where i can find it??? Thanks!

Yeah...the sender is on the oil filter housing by the distributor.
Disconnect the wire and it should be no pressure. If it is still peged then the wire got grounded or your meter is sticking or bad.

always remember that eng. temp. effects oil viscosity. the hotter the eng.
gets' the thinner the oil gets. so at higher temps' oil pressure reads lower.

I had a ply voyager that did the same thing but she was bloweing blue smoke at start up. Oil pressure readings varied all over the place.Rings were bad. I ended up putting in a 33k eng. block. Original had 93k on it and original owner was useing 10w40 to help keep oil at a thicker viscosity.

but that was my problem doesn,t mean this is your situation.

Hey, thanks Bra, I just cleaned up the contacts a little and I've got preassure readings... Nice to know that I don't need a sending unit now...

The oil pressure sending unit is cheap and easy to replace....your symptoms sound like it could be that. Start with the easy stuff.

I said the hell with that rig a while ago chef. Got me a beefy '98 now, but thanks! ps- no more guage probs...

Hey...I just replaced the oil pressure switch in my 97, after many years of getting it to work again....

The d...bugger cost 50 bucks... But now, it works and doesn't drop off at various times.

Apparently, it leaks oil from the oil pressure and "dirties" the contacts to the instrument pack gage at the connector.

Soo... Is the actual issue that the unit is unable by design to do its job within normal pressure specs? Whether OE or Aftermarket?

H*ll, I think that's the jist of it. btw- how does one spell 'jist'? Sounds right in my phonetic head. lol

~May we all have good luck!!

Hey, I have had the same problem with my 98 cherokee. I was told by some guys at the Jiffy Lube where I wash windows (a very lucrative college job :rolleyes: ) Anyways, what happens is when I start it up oil pressure is right on, but as it idles the needle drops. But if I start driving the oil pressure climbs back to normal. One guy told me that it was the fuel pump probably. But the manager of the store told me that it was some sort of ring found where the oil pumps through, and it is much cheaper than the pump and easier to fix. Can't remember exactly what he said. Will ask him again tomorrow at work.

Please......Don't ever listen to anything that somebody at Jiffy Lube tells you. It's possible that they hire the least knowledgable people when it comes to anything remotely mechanical, that way they don't have to pay them anything.

I have such little faith in the people there, that I don't even trust that they can even change oil properly, and in fact have heard many cases in which they couldn't even do that correctly....double filter gaskets...stripped drain plug holes...etc...

The one and only time I went there (in a pinch and hurry), the numb nut comes walking into the waiting room with my air filter and tells me it's "bad", not dirty, but "bad" and that it needs to be replaced, he goes on to tell me that he thinks it's original from the factory and is causing my engine to run rough?????!!!! I had just replaced it when I cleaned my throttle body like 2K before this, and this guy is twisting it in all different directions to show me dirt in it and tell me it's original from the factory. I couldn't resist and had to yell at the manager about them trying to scam me....and who told them to open my airbox anyway!? Then the kid breaks off one of my clips while putting the air filter back in....needless to say I ruined all of their days, didn't pay for the oil change, got re-imbursed for the air box clip and used my share of profanity for the month in about 20 minutes.

So PLEASE PLEASE DO NOT listen to a Jiffy Lube employee telling you that the oil pressure is due to a problem with your fuel pump....which by the way is electric and sitting in your fuel tank, with absolutely no interaction with anything remotely dealing with your oil system.

It's really scary, that place!