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Old 03-09-2012, 02:10 PM   #1
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Oil pressure drop during braking and idle

Replace oil pick tub, new pan gasket, sealed, no oil leaks, I have gone through 2 crap sending units, just put a mopar (from dealer ship) sending unit in. Still having same issue... 1997 wrangler 2.5L... Whats next? Please help thanks.
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Old 03-09-2012, 02:17 PM   #2
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what is it dropping down to?

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Old 03-09-2012, 02:22 PM   #3
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My bad, 0 psi
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Old 03-09-2012, 02:37 PM   #4
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go to an autozone store, grab a mechanical oil pressure gauge and watch it.. yours is computer controlled so this way you can figure out if its your gauge itself..

im assuming you arent experiencing any low end knocking in the engine or else you would've said so..
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Old 03-10-2012, 01:27 AM   #5
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I do not want to alarm you, but I had the same issue with my 2000 (4.0L). Oil pressure was fine when first starting the engine, but once warmed up it would drop to zero at an idle; when stopped at an intersection for instance. Temperature never exceeded normal operating range. I changed the sending unit, then the pump. I then searched online when those had no effect. I found no answer by doing this, but did find a lot of others putting tons of work and money into their Jeeps and not getting anywhere with the problem. I took my rig to a mechanic and had an external oil pressure gauge connected. They ran it and confirmed 0 oil pressure once warmed up. Now whenever you reved up the engine the pressure would jump up, then settled back at 0. Everytime it reached 0 pressure the check gauges light would come on.
After extensive searching for information and talking with people I concluded that the engine had simply started to wear out (oil pressure dropping as a result of it escaping into the spacing between components as the engine reaching normal operating temperature now caused tolerances to be exceeded). A rebuild by a mechanic would have cost me $1500 plus the cost of any worn out parts. For me a better solution was to wait until I found a low mileage engine of the same type for sale and buy it. The Jeep drove just fine like this. Of course that is not to say there was not a problem with it however as I understand they have driven fine for others with the same problem up until the engine blew up. Anyway, I drove my Jeep like this for more than a year before I was able to pick up a new engine, read up on how to install an engine, and found the time to do the swap. Engine never went out on me. I managed to find a used engine with low miles that I bought from a guy who wrecked his Jeep (same year, size motor) for $900. Cost of a few new tools and a couple days from work and no more oil pressure issue for me. I still have the old engine sitting on a stand in my garage. I plan to rebuild it myself as a learning project as I am only a novice when it comes to mechanical work, and if I can make it a good runner again I will find a use for it (ready-to-go backup ). My advice is to consider all your options before you start sinking a lot into your engine. Good luck.
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Old 03-12-2012, 09:47 AM   #6
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thanks everybody
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Old 03-12-2012, 09:57 AM   #7
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Quote:
Originally Posted by Coffeeman
I do not want to alarm you, but I had the same issue with my 2000 (4.0L). Oil pressure was fine when first starting the engine, but once warmed up it would drop to zero at an idle; when stopped at an intersection for instance. Temperature never exceeded normal operating range. I changed the sending unit, then the pump. I then searched online when those had no effect. I found no answer by doing this, but did find a lot of others putting tons of work and money into their Jeeps and not getting anywhere with the problem. I took my rig to a mechanic and had an external oil pressure gauge connected. They ran it and confirmed 0 oil pressure once warmed up. Now whenever you reved up the engine the pressure would jump up, then settled back at 0. Everytime it reached 0 pressure the check gauges light would come on.
After extensive searching for information and talking with people I concluded that the engine had simply started to wear out (oil pressure dropping as a result of it escaping into the spacing between components as the engine reaching normal operating temperature now caused tolerances to be exceeded). A rebuild by a mechanic would have cost me $1500 plus the cost of any worn out parts. For me a better solution was to wait until I found a low mileage engine of the same type for sale and buy it. The Jeep drove just fine like this. Of course that is not to say there was not a problem with it however as I understand they have driven fine for others with the same problem up until the engine blew up. Anyway, I drove my Jeep like this for more than a year before I was able to pick up a new engine, read up on how to install an engine, and found the time to do the swap. Engine never went out on me. I managed to find a used engine with low miles that I bought from a guy who wrecked his Jeep (same year, size motor) for $900. Cost of a few new tools and a couple days from work and no more oil pressure issue for me. I still have the old engine sitting on a stand in my garage. I plan to rebuild it myself as a learning project as I am only a novice when it comes to mechanical work, and if I can make it a good runner again I will find a use for it (ready-to-go backup ). My advice is to consider all your options before you start sinking a lot into your engine. Good luck.
How did you jump to total engine rebuild? Did you try changing the oil pump first?
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Old 03-12-2012, 10:48 AM   #8
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Quote:
Originally Posted by freeskier View Post
How did you jump to total engine rebuild? Did you try changing the oil pump first?

He said he changed the sending unit and the pump.
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Old 03-12-2012, 11:32 AM   #9
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Quote:
Originally Posted by tbensor

He said he changed the sending unit and the pump.
Woops, skipped over that...
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Old 03-12-2012, 11:50 AM   #10
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me too at first
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Old 04-18-2012, 07:04 PM   #11
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2000 Jeep Oil pressure


I am having the same problem and the sensor was replaced. I also just had all my lifters replaced costing $1500 because I had a bad lifter and had multiple engine cylinder misfires. Now my mechanic suggests an oil pump replacement for another $500. I had a 1990
Jeep Sport and the oil pump went at 170K miles. My 2000 now has 164K on it, so I'm concerned the same thing may happen now. I was hoping to get a few more months out of it versus getting a new replacement vehicle this fall. Does anyone suggest I roll the dice and not replace the pump?
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Old 04-18-2012, 07:23 PM   #12
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Changing the pump in mine had no effect, won't if it is internal engine wear that is causing the loss in pressure. I paid $900 for an engine... something to think about before you put a lot into the engine you have now. As far as replacing the vehicle, a 2000 is worth enough in most cases to justify a transplant.

Quote:
Originally Posted by RugPhD View Post
I am having the same problem and the sensor was replaced. I also just had all my lifters replaced costing $1500 because I had a bad lifter and had multiple engine cylinder misfires. Now my mechanic suggests an oil pump replacement for another $500. I had a 1990
Jeep Sport and the oil pump went at 170K miles. My 2000 now has 164K on it, so I'm concerned the same thing may happen now. I was hoping to get a few more months out of it versus getting a new replacement vehicle this fall. Does anyone suggest I roll the dice and not replace the pump?
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Old 05-08-2012, 03:38 PM   #13
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I finally had my oil changed from a 5w-30 oil to a 20w-50 oil and it solved my low idle gauge problem. The sending unit was replaced as well as all lifters in my 4.0. Since I have 165,000 on it, I am riding it into the sunset. Hopefully, some of you can try a heavy weight oil if you continue to have problems. One mechanic suggested a new oil pump, not going there for now.
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Old 07-12-2012, 09:49 PM   #14
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I just had the same problem. changed the oil on Friday and on Saturday the pressure started to plummet at every stop. Two sending units later I took a stab and changed the oil filter. Problem solved. I have never removed a filter with that little oil in it.

It seems this problem can come from lots of places.

Not buying fram again. I only got it because of the sale I am usually a bosch man.

If it helps the service manual says. (see pic)
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Old 02-02-2016, 02:15 PM   #15
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Quote:
Originally Posted by Coffeeman View Post
I do not want to alarm you, but I had the same issue with my 2000 (4.0L). Oil pressure was fine when first starting the engine, but once warmed up it would drop to zero at an idle; when stopped at an intersection for instance. Temperature never exceeded normal operating range. I changed the sending unit, then the pump. I then searched online when those had no effect. I found no answer by doing this, but did find a lot of others putting tons of work and money into their Jeeps and not getting anywhere with the problem. I took my rig to a mechanic and had an external oil pressure gauge connected. They ran it and confirmed 0 oil pressure once warmed up. Now whenever you reved up the engine the pressure would jump up, then settled back at 0. Everytime it reached 0 pressure the check gauges light would come on.
After extensive searching for information and talking with people I concluded that the engine had simply started to wear out (oil pressure dropping as a result of it escaping into the spacing between components as the engine reaching normal operating temperature now caused tolerances to be exceeded). A rebuild by a mechanic would have cost me $1500 plus the cost of any worn out parts. For me a better solution was to wait until I found a low mileage engine of the same type for sale and buy it. The Jeep drove just fine like this. Of course that is not to say there was not a problem with it however as I understand they have driven fine for others with the same problem up until the engine blew up. Anyway, I drove my Jeep like this for more than a year before I was able to pick up a new engine, read up on how to install an engine, and found the time to do the swap. Engine never went out on me. I managed to find a used engine with low miles that I bought from a guy who wrecked his Jeep (same year, size motor) for $900. Cost of a few new tools and a couple days from work and no more oil pressure issue for me. I still have the old engine sitting on a stand in my garage. I plan to rebuild it myself as a learning project as I am only a novice when it comes to mechanical work, and if I can make it a good runner again I will find a use for it (ready-to-go backup ). My advice is to consider all your options before you start sinking a lot into your engine. Good luck.
Thank you for this. I have been reading all over the forums about this issue and no one had any real solutions for the old 2.5L.

I just swapped a blown engine (intake valve broke off and drove 1/4" into a piston. Yikes) and the new engine immediately had the issue of good cold start pressure and 0-20psi warm pressure based on if I was stopped or running.

My sending unit is new, new oil, new filter, and a well cleaned engine before installation. Every part on the engine is new(ish) at this point so all I will need is a good block and head.

Since I am now familiar with an engine swap, sounds like I look for a low mileage engine and then do the swap once it comes time.
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Old 02-11-2016, 03:19 PM   #16
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So I didn't read the threads but as we've been having this same issue and it can have multiple causes I wanted to give you a detail of how to track down the real issue to fix this. First with the engine cold you need to determine if its physical or electronic. So harbor freight sells an "Engine Oil Pressure Gauge" priced right now (2/11/16) for 26.99 about 7 to ship to you. If you own a jeep you need this because it is and always will be a reoccurring problem. Unscrew your "oil pressure sending unit." then find the right fitting in the box. Reverse screw the fitting when it slightly drops screw in the right way be EXTREMELY careful not to cross thread as you will really regret it. (if you cross thread you will most likely have to use a tap and die set to repair it) You need to tighten it down so it doesn't leak. Then screw the hose in. Start the vehicle then watch the gauge. There are a few things your looking for here. One is the gauge bouncing a lot? A little movement is ok. You don't want to see the gauge waving at you. If its waving at you your bearings are most likely wore out and you need to inspect the engine internals so see what exactly is wrong. Two does it show pressure? If it doesn't have pressure your looking at oil pump or worn out motor. Your pressure should be relatively high say 50 or 60 psi when you first start it (check repair book for specs for sure). Check the connections for leaks. Next youll want to either wait for the motor to heat up and the "choke" to kick off. We took ours for a little drive we stuffed the tester inside the engine compartment wedged in between the side fender and fuse box. You might be able to feed the tester around tie the hood down and glance at the gauge as you drive. Drive home look at the gauge. Now it should read 10-20 psi. If it reads 0 you have no pressure and is a physical problem. I've read some places where 7-20 was ok. So you have your cold pressure and your hot pressure. This points to a electrical problem. So the problems could be a bad seal with the oil pressure sending unit, bad oil pressure sending unit (mopar oem is reported to be better because the auto parts store one is foreign junk and if your still having problems it might still be the oil pressure sending unit), the gauge or wiring to the gauge. The good news is that the motor doesn't need rebuild right now anyway. So the steps to take are take dialectic grease(spark plug grease) Take the gauge cluster off and with the car off and key out of the ignition disconnect the battery press the dialectic grease into the connection(female side) so it makes good contact do not over fill just use a small amount. Wipe off excess this is crucial do a good job because you don't want to cross connect the gauges. Restart the car let it warm up and see if this fixes the problem. If it doesn't replace oil pressure sending unit (got my mopar one off ebay for 46.66 dealer had it for 84). The next step would be either replacing the gauge cluster(100+/-) or the wiring harness(no clue as no one makes after market harnesses for the jeep we have) both are expensive.
And just so everyone is clear. An oil pump doesn't cause the oil pressure to change. If you have no oil pressure its most likely your oil pump. If you have low oil pressure its most likely your bearings (main bearings, cam bearings etc). Oil pressure is created by the restrictions in the engine when the bearings wear it allows too much oil through causing low pressure. If your oil pump works intermittently it would cause oil pressure spikes meaning it would be fine for a min then it would drop to 0 back and forth which is why some people have fixed this issue with an actual oil pump. Anyway I hope this helps everyone.
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Old 02-11-2016, 03:39 PM   #17
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I forgot one last thing. I saw a tip on youtube. If you think your oil filter is clogged change your oil but keep the filter. Drain the filter as good as you can. Take tin snips or a rotary cutting saw. Cut the out side metal part to remove the insert of the oil filter. If your oil filter is crushed or got a bunch of sludge. Change your oil every 1000 miles each time taking apart the oil filter to hopefully clear the sludge from your motor.
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Old 02-15-2016, 05:51 AM   #18
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Thanks for the information. I found this thread because I'm having the dreaded low oil pressure problem and did a search on this forum. I put a mechanical gauge on it and changed the oil with 10w-30 conventional. Cold at idle the mechanical gauge read 20 pounds and it's steady. It gradually went down as the engine got warm. When fully warmed up, there is no oil pressure at idle. It very slowly goes up when I rev the engine. I've read a lot of threads where people dumped a whole lot of time and money on this problem and in the end had to replace the motor. Is there anything that has a reasonable chance of working or should I find it a home?
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Old 02-16-2016, 12:33 PM   #19
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Please read my previous post!

@YourShadow07 My previous post is for both the 2.5l and 4.0l and no it doesn't mean you need a new engine. Buy the Engine oil pressure test kit from harbor freight. You will use it more than once if you own your jeep for a long period of time. Most likely its going to be the gauge not getting good contact with the trucks dash side connection. This test kit will tell you for sure if the engine needs replaced or at least repaired or if its just the gauge acting up. The problem we have is with the 2.5l at cold the dash gauge reads 10-20 psi when the "choke" kicks off and you drive it the oil pressure is fine until you stop and idle then the gauge drops to 0psi. Rebuilding a jeep engine is available on youtube if you have general knowledge about mechanic work the basic tools youll need for a rebuild is a machine shop to plane the engine surfaces piston ring compression kit a torque wrench and a socket and set preferably impact variety along with some pb fluid. You will need engine assembly lube and liquid gasket sealer. Where as you can get a rebuilt(reman) engine from advanced auto parts for around 1500 with core trade in plus tax you can rebuild a engine for around 300-500 yourself. Since the problem is reoccurring with a engine swap it is most likely the gauge or if you used the old oil pressure sending unit or got one from an auto parts store.

@Sdavidf Try the trick where you cut the top of your used oil filter off pull out the internal filter and see if there is a lot of thick goop. If you have this problem again change the oil every 1000 miles to try to get as much as you can out of the oil pan. Worst comes to worse take the oil pan off clean it out and then check the oil filter each time you change the oil. The oil filter can become clogged with "engine sludge."

@RugPhD If a thicker oil solved the oil problem you will most likely be headed for worse problems with putting too heavy oil in the engine. The oil pump isn't meant for such a heavy oil and can and will wear it out. You should never use a thicker oil as your engine wasn't designed for it. That heavy an oil is meant for big trucks, big heavy semi truck motors that run on diesel. Truthfully you mechanic doesn't know. We spent 200 on a mechanic that was kin to us only to get no answers and only guesses. THE PRESSURE TEST KIT IS ONLY $27 please invest in it. Read my previous post for instructions on how to use it. The dash gauge could be the problem and your blowing all this money FOR NO REASON!

@Lou1326 READ MY PREVIOUS POST it explains the steps to find out what is really going on with you vehicle. Invest $27 and find out if its just the gauge or an actual problem

This blows my mind after I spent all that time explain how to find out what is really wrong NO ONE is using it to save themselves time and money. I wish someone would have posted it so I wouldn't have had to went through all we did to find out that our jeep has a electrical issue rather than a mechanical issue.
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Old 02-16-2016, 12:38 PM   #20
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@2004CSOTP This is the same issue everyone is having. A new home isn't necessary. You need to invest in the engine oil pressure test kit from harbor freight it was the cheapest I found it. Read my post it explains how to use it and what to do with what you find. It also explains all the possible scenarios that it could be.
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Old 02-22-2016, 06:34 PM   #21
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Quote:
Originally Posted by myjeepbeepbeep View Post
@2004CSOTP This is the same issue everyone is having. A new home isn't necessary. You need to invest in the engine oil pressure test kit from harbor freight it was the cheapest I found it. Read my post it explains how to use it and what to do with what you find. It also explains all the possible scenarios that it could be.
I reread this entire thread. You've spent a lot of time posting and I appreciate it. I didn't buy the harbor freight kit, but I got a sunpro oil pressure gauge from the parts chains and connected it where the sender is/was. Cold at idle it read 20 lbs. Hot at idle it read 0. This was after an oil and filter change. I installed a new Mopar sender (which was made in Mexico) and it also read 0 at idle. The oil pressure, or lack of it, is steady, but I notice that when I rev the engine, it does not quickly build up pressure. It builds up very slowly. Based on your post, it seems worn parts are to blame rather than an oil pump or clogged filter since I changed that shortly prior to testing the pressure.
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Old 03-22-2016, 09:48 PM   #22
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Thank you for this. I have been reading all over the forums about this issue and no one had any real solutions for the old 2.5L.

I just swapped a blown engine (intake valve broke off and drove 1/4" into a piston. Yikes) and the new engine immediately had the issue of good cold start pressure and 0-20psi warm pressure based on if I was stopped or running.

My sending unit is new, new oil, new filter, and a well cleaned engine before installation. Every part on the engine is new(ish) at this point so all I will need is a good block and head.

Since I am now familiar with an engine swap, sounds like I look for a low mileage engine and then do the swap once it comes time.
Im not sure if it could be a ground or what but mine was this way 3 years ago when i bought it. I have since put in a new engine, new computer, several oil pressure sending units before i put a manual one on it until i got comfortable enough that it wasn't really an issue. As well has swapped instrument clusters with others in our little jeep community. And it is still the exact same. It has to be electrical somewhere. I dont hardly see it anymore i guess i have tuned it out.

That being said you shouldn't take it lightly unless you have had a manual gauge on it for a while. Once you are comfortable enough you know its not a problem with the real oil pressure you can take it off.

If anyone gets any ideas about anything electrical or anything I haven't done already let me know would love to solve it some day..

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