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Unread 12-07-2012, 09:33 AM   #1
limited777
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Oil Pressure Gauge Dropping and Rising

Hey guys,

I have done some searching on this but can't come up with a conclusive answer. On my way into the office today the "check gauges" light flashed and I noticed the pressure gauge was down to "0" upon acceleration it went right back up to normal pressure, then during deceleration it would start to drop again.

Once getting into the office I checked the oil and noticed it was still way in the safe but a little low. I'm going to grab some oil at lunch to top it off and pick up a pressure checker so that I know if I should drop it at my mechanic or just order the pressor sensor.

Ideas on this stuff....

FYI: 02 Jeep Grand Cherokee Limited V8, 118k

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Unread 12-07-2012, 09:36 AM   #2
rickcricket
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It is 100% the oil pressure switch. Easy fix but I would spend the extra money and get a Mopar brand. With that being said I did go for awhile on my AZ one (3 years) before I replaced it again with a Mopar one.
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Unread 12-07-2012, 10:15 AM   #3
1AAdam
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X2 pressure sending unit
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Unread 12-07-2012, 10:36 AM   #4
Cirruslydakota
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X3, and only use Mopar.

Sent from inside my 4.0.
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Unread 12-07-2012, 10:47 AM   #5
limited777
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I checked with my local dealership and they have on in stock. The difference in price from ordering it online is about $2 after u calc shipping into it and plus its a weekend so I will have time to get it it rather then wait for it to arrive on a week day.

I guess my only concern was factoring in that it also was low on oil....
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Unread 12-07-2012, 01:05 PM   #6
Wenatchee_Kid
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Ours was doin' that. Our quality mechanic shop replaced the guage (IIRC) for ~$150.
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Unread 12-07-2012, 03:46 PM   #7
rickcricket
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You can just top off as well. The switch going bad can cause oil leaks too,
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Unread 12-07-2012, 11:05 PM   #8
drwolcot
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Seen a couple of these lately..... Mine is doing the same and I just have to get around to replacing it
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Unread 12-16-2012, 12:09 PM   #9
2001WJv8
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what's everyone with a v8 getting for oil pressure?

my power steering pressure hose went bad and the fluid leaked all over the oil pressure sender, but I originally just thought it was the oil pressure sender that had gone bad .... so once I replaced the power steering hose I also replaced the oil prssure switch since I already had the new mopar one.

prior to having this issue (oil pressure gauge dropping to zero at idle because the sensor was soaked in pwr steering fluid) the oil pressure gauge (real gauge - 2001 WJ v8) always stayed around 45-50 psi .... but now after putting in the new sensor it seems to stay around 55-60 psi.

The FSM isn't much help, all I can find in there for the v8 is the pressure should be between 7 and 80 psi. Is pressure of 60 psi indicating some other issue I'm not aware of? I had the oil changed while on a long road trip (4000 miles) recently and they put 5w30 in it - usually run 10w30 - would that make a difference causing the oil pressure to average about 10psi higher? (i'm also currently at about 4500' elevation, whereas usually always have been at 0-400' above sea level)
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Unread 12-17-2012, 09:23 PM   #10
2001WJv8
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anyone?

oil pressure for 4.7L v8?
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Unread 12-18-2012, 12:43 AM   #11
85IrocZ-28
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Your pressure looks fine to me, that is about where mine runs. You don't need it to be maxed at 80psi. I would think your pressure would drop a little with the thinner oil. also, the outside temps Will affect your running temp and oil temps. Cool air or moisture splashing on the oil pan will keep the oil temps lower this time year, keeping the oil a bit thicker, increasing the psi a bit.
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Unread 12-18-2012, 10:06 AM   #12
Galaxie500LTD
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I have the same Jeep, 2001 4.7

I'm running Mobil 1 synthetic 5W30

When I first bought it, the oil pressure gauge would randomly drop to zero and give a CEL.

I replaced it with a Mopar unit and everything was good for 3 months. It ran at about 50-55PSI on the highway and a startup, moved with RPM's in other words, like it should. It read about 40 PSI at idle

Then one day, it went to 65PSI and stayed there. Idle, highway speed, all the time.

Something to check is when you turn the ignition on, the gauge should read zero. Don't start it, just turn the key to the on position, don't engage the starter. If you are getting 65PSI (or whatever your gauge seems to be stuck at) then your sending unit has gone bad again. I also checked all of my connections etc. My gauge read 65PSI without the motor running...

I checked gauge functionality by pushing in the odometer reset button and turning the key to the on position, then letting go of the button, your gauges will do a check and move from stop to stop.

Here's a YouTube link of someone doing that:


I also checked all of my electrical connections etc. I did have an engine code P0523... It never did give me a CEL, and it never came back again after I pulled my neg. battery terminal even though my sending unit was still buggered... don't know why.

Anyway, my dealership was nice enough to give me a new replacement Mopar sending unit after I convinced them my basically new sending unit was screwed. You can swap it out without removing the oil filter. It's tight but I did it. You have to remove your air box, then you can squeeze your fingers in there. You won't lose any oil.

FWIW... here's the 3 month old sending unit, and my newer one side by side. Different production #'s... don't know if it's something to look for or not...the NEWer one is on the left.

p1010014.jpg
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Unread 12-18-2012, 12:06 PM   #13
2001WJv8
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Quote:
Originally Posted by Galaxie500LTD View Post
I have the same Jeep, 2001 4.7

I'm running Mobil 1 synthetic 5W30

When I first bought it, the oil pressure gauge would randomly drop to zero and give a CEL.

I replaced it with a Mopar unit and everything was good for 3 months. It ran at about 50-55PSI on the highway and a startup, moved with RPM's in other words, like it should. It read about 40 PSI at idle

Then one day, it went to 65PSI and stayed there. Idle, highway speed, all the time.

Something to check is when you turn the ignition on, the gauge should read zero. Don't start it, just turn the key to the on position, don't engage the starter. If you are getting 65PSI (or whatever your gauge seems to be stuck at) then your sending unit has gone bad again. I also checked all of my connections etc. My gauge read 65PSI without the motor running...

I checked gauge functionality by pushing in the odometer reset button and turning the key to the on position, then letting go of the button, your gauges will do a check and move from stop to stop.

........]
thanks, my mopar replacement sender has only been in 2 weeks but immediately went on a 2000 mile roadtrip ... your description describes what my gauge was doing right after I put it in (fluctuating w/rpms) and now how it seems locked at 60psi - but for the last 12 years/since new it has always gone to about 45psi and stayed steady. I didn't think to check the gauge operation, i'll see if it is operating normally and go from there.
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Unread 12-18-2012, 04:45 PM   #14
2001WJv8
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checked the gauges and sure enough all the needles sweep then the oil goes to 60 psi with the engine off.... so much for "buy mopar" when it comes to sensors - this one was good for 2 weeks/2000 miles

edit: replaced it with another new mopar unit ... here's a photo for anyone searching - may help with that stupid red clip:

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Unread 01-12-2013, 06:40 AM   #15
ginobrownt
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Hello guys ,

I have Grand Cherokee 2002 model , my oil pressure was reading high so my mechanic advice me to change the sensor, which I did but after using the new one for weeks, now s ready pressure low, what might be coursing the problem. Any ideas
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