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Old 02-06-2012, 07:13 AM   #1
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Cool Oil Change & Now the pressure drops when hot and idling

I have a 2003 Wrangler that has a LOT of miles on it. We just had the oil changed. Everything was fine on the way home. But the next day, we noticed that the oil pressure is fine when the engine is cold and when it is running, but when it is idling at stop lights and signs, it drops.

I have seen some threads that suggest it might be the sendig unit and that getting a mechanical gauge from AutoZone will tell us if the pressure is really dropping. We plan on doing that.

I am trying to get together all the possible reasons this could be ahppening. My husband thinks it's the pump (he's an alarmist), but I think it's odd that it started right after the oil was changed and want to check other stuff first.

Any clues as to what else might cause the drop?

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Old 02-06-2012, 07:15 AM   #2
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Its a mechanical pump, so its highly unlikely that it would be that. Do you notice any unusual sounds coming from the motor? How many miles does it have and how low is the pressure at idle? What oil did you have in before? (IE 5w-30? Synthetic?)

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Old 02-06-2012, 07:27 AM   #3
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Why shouldn't the oil pressure drop at low rpm?

What does it "drop" to?
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Old 02-06-2012, 07:33 AM   #4
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A drop is normal at idle, depending on what it drops to. It will definitely be lower at idle when warm as well, the oil will become thinner and will flow easier, offering less resistance as it passes through the pressure sending unit, and the rest of the motor, resulting in a lower pressure reading.
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Old 02-06-2012, 08:54 AM   #5
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Your 03 does not have a real time oil psi gauge. If it's dropping low enough for you to see it it's a problem. It's probably the the oil pressure sensor. The way it works is if the PCM sees sees at least 7 psi it marks in the middle of the gauge. Less and it kicks on the check gauges lamp and shows 0.
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Old 02-07-2012, 05:11 PM   #6
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Quote:
Originally Posted by mealohaoe View Post
I have a 2003 Wrangler that has a LOT of miles on it. We just had the oil changed. Everything was fine on the way home. But the next day, we noticed that the oil pressure is fine when the engine is cold and when it is running, but when it is idling at stop lights and signs, it drops.

I have seen some threads that suggest it might be the sendig unit and that getting a mechanical gauge from AutoZone will tell us if the pressure is really dropping. We plan on doing that.

I am trying to get together all the possible reasons this could be ahppening. My husband thinks it's the pump (he's an alarmist), but I think it's odd that it started right after the oil was changed and want to check other stuff first.

Any clues as to what else might cause the drop?
My 2004 wrangler just started doing this Friday When I get to an idle, the gauge drops all the way down and sounds the check gauge warning alarm/light, bouncing up and down slowly. When I tap the gas pedal, the gauge responds slowly back to normal. It did not do this all weekend and just today started again. I'm going to replace the op sensor this weekend.
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Old 02-07-2012, 07:11 PM   #7
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I have had this happen to me a few times with both of my 5.2 powered vehicles . It seems to happen with semi synthetic high mileage oils. I have since been sticking to conventional 10w-40. I know the feeling ,it scares the crap out of you.
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Old 02-07-2012, 07:22 PM   #8
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Stupid question and may be way off-----are you sure they put enough oil in the crank???
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Old 02-08-2012, 07:13 AM   #9
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Old 02-08-2012, 07:39 AM   #10
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My 97 was doing the same thing. I changed out the sending unit and it was still reading the same thing. so I put a mechanical gauge from advance in and found that my oil pressure was fine. Im not sure about your yr wrangler but i have read that the earlier TJ's had problems with the stock oil gauge.
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Old 02-08-2012, 11:58 AM   #11
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5w30 was giving me low oil pressure at idle. And took long enough to increase after engine start that a light on my dash would come on for a moment. I switched to 10w30 and no more issues.
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Old 02-08-2012, 06:37 PM   #12
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i am having this same problem. its a new engine (rebuilt) and i bought the jeep used so ill have to try changing the oil and if it fixes the prob. im new to the site and am perusing the post before i start a thread when one exist.
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Old 02-08-2012, 10:37 PM   #13
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Ok, I had the same problem. My 97 would loose oil pressure at idle and the check gauges light would come on. I too put a mechanical gauge in. Lowest the mechanical gauge ever got was 20 at idle. Replaced the sender 3 times. Day after day the gauge would drop. Then one day I put KC lights on the Jeep. Pulled the dash to put in wires and noticed on the back of the dash, each gauge had 4 screws for the circuit board. Well, I took a screw driver and just turned all 4 screws just a bit for new "contact" Put the dash back in and buttoned it up. That was 6 months ago. I have NEVER had the gauge fall below 20 and the check gauges light come on since. Did I fix it??? I did something right. Good luck and let me know if you fix your problem too.

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Old 02-14-2012, 08:04 PM   #14
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Today I finally got around to installing a new Oil Pressure switch. I'll have to wait till tomorrow to see if it solved the problem. NAPA had it for $11.00, hopefully it will solve the intermittent low pressure problem.
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Old 05-06-2012, 06:48 AM   #15
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I had the same problem, I have a 2004 Unlimited with 80,000 miles. I changed the sending unit (oil pressure switch) and the problem persisted. I read a thread that you need to buy it from the dealer because the ones from autozone don't give an accurate reading. I got it from the dealer, the problem continued. I finally replaced the oil pump, which i bought at autozone and replaced the rear mail seal while i was at it.
I am now a very happy camper, love my jeep, no more oil pressure problems.
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Old 05-06-2012, 08:51 AM   #16
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Quote:
Originally Posted by mealohaoe
I have a 2003 Wrangler that has a LOT of miles on it. We just had the oil changed. Everything was fine on the way home. But the next day, we noticed that the oil pressure is fine when the engine is cold and when it is running, but when it is idling at stop lights and signs, it drops.

I have seen some threads that suggest it might be the sendig unit and that getting a mechanical gauge from AutoZone will tell us if the pressure is really dropping. We plan on doing that.

I am trying to get together all the possible reasons this could be ahppening. My husband thinks it's the pump (he's an alarmist), but I think it's odd that it started right after the oil was changed and want to check other stuff first.

Any clues as to what else might cause the drop?
I can almost guarantee that the shop used 5w-30. It's warm out now so you need 10w-30. It's in your manual. Try using 10w-30 before you go throwing money at parts, it's what should be in there anyway. I've had this happen before.

Edit- Just noticed the date of the original post....
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Old 05-06-2012, 08:51 AM   #17
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Im assuming its normal.. that it'll read about 40 PSI at lower speeds and about Idel... closer to about 50-60 on take off and higher speeds... I've driven two jeeps.. and they seem to do the same thing... No matter the oil type... once it gets nice warm and plyable the pump has less resistance so the oil gets where it needs to alot faster and easier... I've seen it get as low as 30 in my 95 YJ... but my TJ doesnt get any lower then 40 PSI when its warmed up which seems normal to me...


However.. just as harry said... make sure your using 10-30 at this time of the year... it needs that type of oil to keep everything lubed and cooled while driving.. if Im correct 5w-30 is to be used at 32 or below only unless your car (not your jeep) is set to use it all year round
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Old 07-12-2012, 09:55 PM   #18
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I had the same problem. I replaced the oil pressure sending unit twice because of reding forums. Then took a stab and changed new oil filter out. The problem was caused by the oil filter. I have never removed one with that little oil in it. It runs great now.
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Old 07-13-2012, 06:24 AM   #19
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yes, I agree, most fast oil change places use cheap filters & sometimes cheap oil. always use top quality oil & filters, it is your engines life blood. be religious on oil change intervals. take of your engine it will take care of you, most of the time .LOL
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Old 07-24-2012, 10:29 PM   #20
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Quote:
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yes, I agree, most fast oil change places use cheap filters & sometimes cheap oil. always use top quality oil & filters, it is your engines life blood. be religious on oil change intervals. take of your engine it will take care of you, most of the time .LOL
Yes, you are right. And I am not one to let anyone stick their head under the hood of my jeep. I changed the oil myself and got a Fram Tough Guard filter because it was on sale with the oil at auto zone. Next time I'll just pay full price and get the filer of my choice.

But if anyone is tracking this problem down it is good to know that it can be as simple as a bad oil filter.
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Old 08-27-2012, 07:08 AM   #21
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hope Im not beating this to death...

Hi all, new to the board... Just purchased my 4th wrangler, 02 sport, over my lifetime.. I bought it from a guy that was having this same problem, so he said, about 10,000 before I bought it.. He brought it to the Jeep dealer, and he showed me where they rebuilt the whole top end and replaced the the whole top end and new sending unit... Dont ask me why, but he told them what you are describing.. Receipts show nothing of replacing pump ect..

Right after I purchased it, as I was pulling out of his driveway.. The exact symptoms showed up.. I test drove it, like I stole it, with no noises, good power and everything worked.. At idle on the way home, not every stop, it would drop to zero and cause the CEL to come on.. I would just tap the pedal and it would come up.. again no noise or problems taking off or loss of power... Im lost and hope I didnt get screwed... any ideas... thanks
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Old 08-27-2012, 10:20 AM   #22
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Hi all, new to the board... Just purchased my 4th wrangler, 02 sport, over my lifetime.. I bought it from a guy that was having this same problem, so he said, about 10,000 before I bought it.. He brought it to the Jeep dealer, and he showed me where they rebuilt the whole top end and replaced the the whole top end and new sending unit... Dont ask me why, but he told them what you are describing.. Receipts show nothing of replacing pump ect..

Right after I purchased it, as I was pulling out of his driveway.. The exact symptoms showed up.. I test drove it, like I stole it, with no noises, good power and everything worked.. At idle on the way home, not every stop, it would drop to zero and cause the CEL to come on.. I would just tap the pedal and it would come up.. again no noise or problems taking off or loss of power... Im lost and hope I didnt get screwed... any ideas... thanks
Make sure it has 10w-30 oil in it, and a good filter. Also could change the oil pressure sensor next to the filter. With all the work that has been done to it, it should be an easy fix. I'd say if the guy you bought it from paid dealer prices for all of that because of a bad sensor, he got screwed, lol.
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Old 08-27-2012, 10:28 AM   #23
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Is it the check engine light as you stated or is it the check gauges light that comes on when the pressure gauge drops? If its the check engine light, you may have some real issues, if its the check gauges light, I would replace the oil sending unit ($35) see if that fixes it.
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Old 08-27-2012, 03:23 PM   #24
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Quote:
Originally Posted by Plowboy1970 View Post
Ok, I had the same problem. My 97 would loose oil pressure at idle and the check gauges light would come on. I too put a mechanical gauge in. Lowest the mechanical gauge ever got was 20 at idle. Replaced the sender 3 times. Day after day the gauge would drop. Then one day I put KC lights on the Jeep. Pulled the dash to put in wires and noticed on the back of the dash, each gauge had 4 screws for the circuit board. Well, I took a screw driver and just turned all 4 screws just a bit for new "contact" Put the dash back in and buttoned it up. That was 6 months ago. I have NEVER had the gauge fall below 20 and the check gauges light come on since. Did I fix it??? I did something right. Good luck and let me know if you fix your problem too.

Will
This kind of stuff is exactly why I love this site. This could be a simple fix for things like this that go wrong and it would be a bitch to figure it out otherwise. Thanks, might help out in the future
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Old 08-27-2012, 05:03 PM   #25
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Since it happened right after an oil change, and if there is enough oil of the right viscosity grade in it, another vote for filter.

Most engines seem to do fine on whatever oil filter is on sale, but some do not. (Also, occasionally, oil filters can be just defective right out of the box no matter who makes it.)
FWIW, I will use Mopar, Purolator, Mobil1/K&N, Wix/NAPA Gold or Baldwin on my 4.0...never would use STP, A-C Delco, or Fram (unless maybe it was the high end one Fram makes.) My 2 cents worth.
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Old 09-01-2012, 09:16 AM   #26
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First, Thanks for all the replies... and now Muther Fer..... I went to a local 4x4 shop that I use for help and parts... Hardcore wheelin guys... They told me that with the heat here, that I should put in 10w40? to try and maybe some lucas to try... and its the check gauges light kshaws21, to keep pressure up a bit with over 100 degree heat... Made sense to me... then if that didnt work, put a manual gauge on and go from there..

Just to back up.. the low pressure at idle... which only occured after stopping, sitting for a few minutes at the shop, gas station ect... continued on this trip... tap the gas a couple times before I left and back up... starting cold pressure up at idle and sitting in neutral....

Now the real kicker... I also have an AC prob... cold on the resevior side to condenser. but not blowing cold... found out the vent door motor was gone, while playing with it and talking to the guys at the shop on the same trip... anyway.. they had an old one, took it to change out when I got home... In the mean time for the way home, and to try the air, I manually changed the vents... to see if it would blow cold... Vents blew warm but cooler than the temp outside with the top off..

Anyway to get to the point... this is all to set up for a big prob... I was driving home, playing with max air... and nothing showing on the heat gauge or oil gauge to warm me of anything... I start getting what sounds like a lifter tick... WHAT THE FFFFF... this was all replaced right? pulled over only a few miles from home and couldnt see anything under the hood... drove home parked and looked closer... now for the punch line..

The coolant looked full in the resevior.. the top hose looked buldged? fffff....I tried to open the plastic oil fill cap... stuck.... what? couldnt get it off with a big pair of chanel locks without feeling like I would break it... coolant overflow looked darker... checked oil.. frickin hot stick.... no sign of coolant and looked clean but not as clean as it was when I bought it... hmmmmmmmmmmm.... What sounded like lifter tick got worse...

I let sit for a couple hours... opened oil filler cap... saw oil when I started it, no coolant, but lifter tick not as bad... minor... coolant cap off and oil in it... water out the muffler drip out of muffler itself, which is halfway down the exhaust.. Im screwed...

I probably have a cracked head now.. no warning at all... I think I screwed up pushing the system with the air on...

Dont know where to go from here... Really freaked out with the low oil pressure and now this.. This guy that sold it to me had to know all this... I dont know if all the work before on the top end, and new radiator put in, is just a lemon chase in a circle... with the oil pressure problem, air cond, new radiator ect... any suggestions... I know I puked all this out, but very frustrated and stressed with only just getting it home... thanks ahead of time...
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Old 09-01-2012, 03:14 PM   #27
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The ambient air temp has no effect on your engine temp. You said that the temp gage did not show hot so you are probably running in the 210 deg range your supposed to be in. That means your engine is 210 degrees weather it is 60 degrees outside or 120.
Multi grade oil is only important if you live in areas where the temp is cold when you start the engine. 5W-30 and 10W-30 are both 30wt at operating temp. They only act like the thinner wt at cold temps.
See here.Motor Oil Viscosity Grades Explained in Layman's Terms

Is your top hose still bulged after the engine cooled?

Clear water in the muffler is normal and is the result of the ethanol in the fuel. That is why newer exhaust systems are made of stainless steel.The molecule for alcohol is made up of Carbon Hydrogen and Oxygen. Burn it and you are left with water, H2O.

You did not push your system with the air on as you said nothing changed in engine temp. Other than using more gas for the compressor and pre-heating the air in front of your radiator the air did not cause any problem.

I don't know if the 4.0 has this feature but there are some engines that require a checkvalve in the oil filter to prevent backflow. Some crossreferenced filters may fit but may also lack the checkvalve. This is true for my '05 Toyota V-8.

You may just have a sitcky lifter.
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Old 09-01-2012, 09:16 PM   #28
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You get water with pure petroleum, too. Unless you smell burnt coolant, I don't know if I'd worry about it.
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...I don't know if the 4.0 has this feature but there are some engines that require a checkvalve in the oil filter to prevent backflow. Some crossreferenced filters may fit but may also lack the checkvalve. This is true for my '05 Toyota V-8...
An oil filter without that anti-drainback valve is pretty rare, regardless of what the liars at the dealership parts counter may say. If it weren't there, it wouldn't cause low running oil pressure though, just maybe lifter rattle at startup. (My Toyota dealer once told me to use their OEM filters because they had this valve. I told them to show me a cross, or most any other oil filter, that didn't have it.) I can't really say what's going on with this engine from this side of the web.
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Old 09-05-2012, 11:53 AM   #29
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The hose is soft now.. I started it for the first time this am.. in a couple days.. lifter tick upon start up but went away within a min or two... looked into the cover with the cap off and could see oil come up.. seems like it took a couple min? suppose to take that long?... Going to take the pan off this weekend to take a look... Still worried about the small bit of oil on the radiator cap... its definitely a new radiator and cap.. Was going to put a melling high volume pump in to be safe, but would like some input if people think you really need it... Its fricking 100 here everyday... Then if all looks ok in the pan, Im going to flush the radiator and do a change with 10/30 and a new filter.. any suggestions on the filter? was thinking about running cheaper oil for a bit with some commercial cleaning or ATF for a bit to clean it out.. then do another change ... any thoughts on that... Still dont get why it started ticking all of a sudden now... and does anyone have any suggestions why my AC is cold from the lines going into the condenser, but warm on the otherside... and inside the jeep... also does anyone know if the vents are vacuum actuated or electric...

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