Oil Pressure going lower and lower and lower

[FaultyLine]

For approximately 6 months, my oil pressure has been slowly going down. When I first got the jeep a year or so ago, hot idle was around 30-40PSI and cruising was 50PSI. Today, hot idle was 5 for a few minutes, then the gauge dropped to 0 triggering the check gauges light. A little more RPM got it to register again. Cruising today was anywhere from 20-40PSI; it kept moving all around while driving the same speed. I've been reading up on this and it's almost certainly because my Jeep has 180K on it and the engine is just starting to show it's wear :repair: I've also always had a loud tick coming from the top end - which I'm sure has to do with a lifter. More concerning to me is the slight knocking I've started to notice at idle. What's more strange it that it only happens sometimes, hot or cold.

I was thinking of replacing the oil pump with a new OEM one (seems that HP and HV pumps aren't worth it in the 4.0l) to *see* if that even makes a difference, but am concerned it may just be a waste of time/money as it seems that my engine is just old and worn out. A new oil pump isn't going to fix that.

I'm hoping to get some feedback on what others have done when their jeeps have exhibited low oil pressure. What makes sense to try before I start taking things apart. *SHOULD* I go for a new oil pump for the heck of it? Is is better to just rebuild it and be done with these issues?

'01 XJ, 180K, 10W-40 (per manual), oil replaced every 3K-7K (maybe that's the problem :eyes since I've had it.

 

[Johnnie Walker]

Hi Mitch!
Buy/rent/borrow a mechanical oil pressure gauge, and confirm your oil pressure. Hose should be long enough so you can have the gauge in front of the windshield on the cowl so you can read as you drive. AS far as ticking, could be an exhaust leak. But lifter tick is common.
What oil filter are you running?
With all of this, I would recommend an oil analysis. OAL- oillab.com , Blackstone labs, etc.

Also, maybe check and confirm your flexplate bolts are tight.

 

[FaultyLine]

I should have thought of the mechanical gauge - I see that on almost ALL oil pressure threads. I'll start there!

I'm running a Bosch something-or-other. I've learned to stay away from no-name white generic filters and FRAM ones.

What kind of information could I expect back from the oil analysis, I never even knew there was such a thing.

I'm not sure what a flexplate is - but I'll figure it out and check.

 

[FaultyLine]

Just looked up a flexplate - got it! Out of curiosity, how could a lose flex plate cause oil pressure issues? I don't fully understand the mechanics of the engine and trans yet - so please excuse the silly question.

 

[Johnnie Walker]

Just looked up a flexplate - got it! Out of curiosity, how could a lose flex plate cause oil pressure issues? I don't fully understand the mechanics of the engine and trans yet - so please excuse the silly question.

The flexplate comment was about your "knocking" sound.

 

[mcguyver_xj]

unfortunately if your oil pressure is dropping that low and you do have a lifter tick and a knock its time for a new engine as you have been having oiling issues yes the 4.0 is very reliable as long as its taken care of i am actually going to be buying an xj with 185k and it has a nasty rod knock...

yes a flexplate could be knocking but knocking and ticking coupled with terribly low oil psi i think the rods wanna come out and play...

good luck

 

[Ronbo]

Don't jump to expensive conclusions. Do basic checks - check the real oil pressure, not the gauge. Which oil do you run? Have you checked the level in a while? What filter ? Look into the valve cover - is the motor gunked up?

 

[GrimmJeeper]

unfortunately if your oil pressure is dropping that low and you do have a lifter tick and a knock its time for a new engine as you have been having oiling issues yes the 4.0 is very reliable as long as its taken care of i am actually going to be buying an xj with 185k and it has a nasty rod knock...

yes a flexplate could be knocking but knocking and ticking coupled with terribly low oil psi i think the rods wanna come out and play...

good luck

I agree 100% with this post, start looking for an engine.

Or, time to build a stroker!

 

[old_man]

If it turns out the oil pressure is actually low, and changing the filter doesn't fix it, drop the oil pan. There are specs on the clearances on the oil pumps you can check.

I would pull a rod cap and main bearing cap and take a look at the bearings and journals. I have been known to throw a fresh set of bearings into a motor if the journals are still good. My wife ran her Chrysler Pacifica out of oil. I swapped the rod and main bearings and have put another 150K on it for around $75.

 

[Hillbilly XJ]

If it turns out the oil pressure is actually low, and changing the filter doesn't fix it, drop the oil pan. There are specs on the clearances on the oil pumps you can check.

I would pull a rod cap and main bearing cap and take a look at the bearings and journals. I have been known to throw a fresh set of bearings into a motor if the journals are still good. My wife ran her Chrysler Pacifica out of oil. I swapped the rod and main bearings and have put another 150K on it for around $75.

It has been many years ago but I did the very same thing on a Slant 6 another engine that Chrysler Corp built. It was well known for a very long life also.

How good were they only us old guys would know. I the late 60's I think Checker Car Company sued Chrysler when they backed out of a contract to supply them the Slant 6's, paid a huge out of court settlement at the time. Reason they had lost about all their fleet business to Checker because they lasted forever. You could not tell a new one from a 15 yr. old one lol.

 

[FaultyLine]

Don't jump to expensive conclusions. Do basic checks - check the real oil pressure, not the gauge. Which oil do you run? Have you checked the level in a while? What filter ? Look into the valve cover - is the motor gunked up?

I'm running factory spec oil - 10W-40. I checked the oil the other day - it's at the right level. It only has about 1000 miles on it ATM - just replaced it recently. I'm running a BOSCH filter. I had the valve cover off about a year ago and it looked nice and clean - but I haven't take a look recently. I'll check that as well. I was reading that a gummed up intake on the oil pump can cause pressure issues.

 

[FaultyLine]

If it turns out the oil pressure is actually low, and changing the filter doesn't fix it, drop the oil pan. There are specs on the clearances on the oil pumps you can check.

I would pull a rod cap and main bearing cap and take a look at the bearings and journals. I have been known to throw a fresh set of bearings into a motor if the journals are still good. My wife ran her Chrysler Pacifica out of oil. I swapped the rod and main bearings and have put another 150K on it for around $75.

Thanks for the advice. I do the oil changes myself a filter hasn't made a difference. I'm not too familiar with the engine mechanics yet - Are the main bearings something that can be gotten to w/o pulling the engine? I'm going to take a look @ the rod bearings when I take the pan off to check the oil pump.

 

[87manche]

yes, you can do bearings in the vehicle.

 

[paddlernate]

The knock you're hearing could be piston slap, where the cylinders have worn enough to where the piston can rattle around in the bore. It can sound a lot like a rod knock. If it turns out the oil pressure is actually low, I'd perform a compression test/ leak down test on the cylinders and see if you still have decent compression. No use putting work into the oiling system of an engine that's on it's last legs all around. If, however, you find compression to be ok, you might as well do the rod and main bearings while you're in there doing the pump, and if you go that far, you might want to think about the timing chain as well.

 

[HappyDog]

... I've also always had a loud tick coming from the top end - which I'm sure has to do with a lifter. More concerning to me is the slight knocking I've started to notice at idle. What's more strange it that it only happens sometimes, hot or cold.

You *may* be experiencing the symptoms of a worn-out engine, but make sure first!

As others have said, check the oil pressure with a mechanical gauge you can read as you drive around.

A vacuum gauge can be used for a quick check of the condition of the engine . Look at this web page for details: http://www.classictruckshop.com/clubs/earlyburbs/projects/vac/uum.htm

The "loud tick coming from the top end" *may* be the solenoid on the evap canister on the passenger side firewall between the engine and the hood hinge. Both my 1997 and 2001 make a quite noticeable TICK at about 5-8 ticks per second while the engine is idling and I have traced it to that solenoid which meters the flow between the evaporative canister and the intake manifold.

The "slight knocking" could be anything from piston slap to flex plate issues (loose bolt or a crack developing in the flex plate. Be careful about tightening the flex plate bolts -- the torque spec is actually quite low -- look it up before heaving on the wrench!

 

[FaultyLine]

Thank you everyone for the information, suggestions and advice - I REALLY appreciate it. Looks like a have a fun weekend of taking my heep apart!

 

[GrimmJeeper]

if you're going to pop the oil pan off and check your rod and main bearings i'd suggest waiting till it's not raining so bad in socal to do so, there's a lot of moisture in the air right now.

just a thought. :cheers:

 

[FaultyLine]

Thanks GrimmJeeper! I've been working quite a lot lately, so my jeep is just sitting right now. I haven;t had a chance to do ANY of the tests suggested yet I'm hoping to get to it this weekend or next.

 

[old_man]

By the way, go ahead and do a compression test, both wet and dry. That way if you are looking at doing the bearings, you will have an idea of what condition the cylinders are in.

 

[NOTNSUV]

Oil analysis detects wear metals, contaminants, additives, cleanliness, viscosity, and acid level. Consider it as blood work for your engine. A comprehensive and consistent oil analysis program is a great tool to trend your vehicles condition and is widely used in industry (mining, fleet operations, drilling, generators, racing, etc.) for engine oil, hydraulic systems, gear boxes, etc. Oil analysis can also detect the cause of an acute problem as well as the trend.

A quality lab will tell you where any wear is coming from in your engine by determining the types and quantities of wear metals in your oil. They can pin it down to cam or main bearing, cylinder walls(iron), rings, and even an oil cooler in a diesel engine (if copper alone is found).
They will measure the level of contaminants in your oil due to ingress of silica (dirt) and perform a 'particle count' that comes in the form of an industry standard number that is compared to the ISO4406 chart. The report can even tell you if your air filter needs changing or if it has been neglected in the past.
Also, the condition of the additive package in your oil is measured and documented. A jug of oil is 85% carrier, whether petroleum or synthetic, and 15% is additive that actually does the work. The 'oil' is only the carrier that delivers the additive to where it needs to be. Oil DOES NOT wear out, it just gets dirty. That dirt will contribute to the depletion of the additive package in the oil. The additives are intended as sacrificial in order to minimize wear on components. If oil is kept clean, it will not 'wear out' and can last indefinitely, including the additives.

In your case, oil analysis can point you in the right direction as to what you're looking for when tearing down. Otherwise, it can identify a problem with a component before it becomes critical or a catastrophic failure.

I use Kleenoil bypass filters on everything I own, including the XJ. http://www.kleenoilusa.com/index.php/products/kleenoil-products/kleenoil-bypass-filter-systems
and use Wear Check in Cary, NC as my oil analysis lab, again on everything I own.

Feel free to PM if you want to take the discussion further.