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Old 03-07-2012, 07:44 AM   #1
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oil pressure sending unit - oem or not?

Alright, I bought a '99 TJ in november of 2011. Enjoying it very much. Wish warm weather would get here just had a few teases so far.

The problem. I noticed yesterday at a stop light my check gauges light was on. So I checked the gauges only to discover in horror that my oil pressure gauge was at zero. .

So i immediately shut off engine. I got out and looked under jeep expecting to see oil everywhere but it was dry. I got back in and started the jeep (pressure was back up some still not normal) and pulled off the road.

I had just checked the oil level before I left home. I checked it again. OK fine. I checked the radiator fluid for signs oil was leaking into it. Fluid looked good. I started the engine and the gauge was not reading zero but hovering just above maybe about 8 or 10 psi. I revved the engine and the gauge climbed up near 40. Usually it reads about 37ish at idle and 44ish at highway warm.

I let it idle again and it settled on about 8 or 10 again. I got out to listen to the engine. sounded fine. completely normal. engine temp was fine too. I decided to take it home and get on the net.

So here I am. I've read about the sending unit going bad and thinking of replacing it. Autozone has it for about $44.00 - dealer $66.00. Which one should I get. Will the OEM work any better or last longer? Is it worth it?

Also if it was reading zero but running fine surely that means that the sending unit is the culprit right? It wouldn't run fine, sound fine, at zero? It scared the crap out of me. Could it be the oil pump?

What if i replace the sending unit and the new one does the same thing? I don't have a pressure gauge to hook up to it. They run about $60.00. Does Autozone (or someone else) lend one?

BTW I changed the oil about 1500 miles ago to full synthetic. Could this be part of it?

Thoughts, ideas, concerns all appreciated - thanks

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Old 03-07-2012, 08:00 AM   #2
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The first time mine went bad, I dropped the pan, checked all the bearings, replaced the oil pump, oil and filter. To make a long story short....a few weeks later I learned the oil pressure sender went bad not the engine or a clogged filter.

I have lost 2 senders since. My suggestion is buy 2, replace the bad one and cary one in the console. You might price shop other auto parts houses too your price seems a bit high.

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Old 03-07-2012, 08:14 AM   #3
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Yeah unfortunately $44.00 is the cheapest I found. Another dealer has one for $57.50.
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Old 03-07-2012, 08:35 AM   #4
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Why is the price so high. 2005 was only $7.50 at NAPA and had to be ordered.
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Old 03-07-2012, 08:41 AM   #5
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Yeah I bought one from carquest 2 years ago for $17
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Old 03-07-2012, 08:51 AM   #6
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I dont want to be the one to give you the bad news, but mine was doing the same thing. The oil pressure is fine when the engine is cold, but as soon as it gets warm the pressure goes to crap. At idle the pressure drops to zero and at 2500 rpm's, the pressure is between 20-30.

Reading other threads on this forum I was thinking that it was the sending unit going bad so I replaced it. The new unit showed the same pressure. I hooked it up to a manual gauge, and it showed the pressure was in fact very low.

My next step was to replace the oil pump. I was able to buy all the parts for about $150. It took me a couple of evenings after work to get it replaced. After I got the new one in place and fired up the jeep the pressure was better when the engine was cold. But, as soon as I went for a drive, the pressure went back down when it warmed up.

This only leaves me knowing that I have a worn engine. I put some heavier oil in it, and now I'm going to just drive it until it gives out. Hopefully, you will have better luck thank me.
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Old 03-07-2012, 09:00 AM   #7
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J-No, sorry to here that. God I hope this isn't the case.

----------------------------------

I took the electrical plug off and it had oil in it so I'm thinking maybe it is the sender and that's all there is to it (crosses fingers). I mean there shouldn't be oil in the plug of the sender right?

The sender is just above the oil filter right? (it's a 99 4.0)
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Old 03-07-2012, 09:01 AM   #8
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This is a common problem with the 4.0. Change the sensor and you will be fine. I had the same problem. Sensor is the easiest and cheapest start to troubleshooting.
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Old 03-07-2012, 10:28 AM   #9
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k - update,

Got new sensor from Autozone cause i needed a deep socket also (1 1/16"). Put it in and now the little gauge reads 40 at idle when warmed up.



Oh yeah happy days are here again!!
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Old 03-07-2012, 10:31 AM   #10
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I always recommend OE for sensors like the oil pressure sender. It took me 3 Autozone oil pressure senders for my son's Grand Cherokee before I got one that worked properly.
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Old 03-07-2012, 11:06 AM   #11
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Alright took it for a drive and it idles at about 35ish and on highway it sits about 44ish.

Glad it was no major work, I just finished replacing front seal and clutch in my Toyota truck - not in any mood for more auto work.
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Old 03-08-2012, 01:09 PM   #12
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Quote:
Originally Posted by J-No View Post
I dont want to be the one to give you the bad news, but mine was doing the same thing. The oil pressure is fine when the engine is cold, but as soon as it gets warm the pressure goes to crap. At idle the pressure drops to zero and at 2500 rpm's, the pressure is between 20-30.

Reading other threads on this forum I was thinking that it was the sending unit going bad so I replaced it. The new unit showed the same pressure. I hooked it up to a manual gauge, and it showed the pressure was in fact very low.

My next step was to replace the oil pump. I was able to buy all the parts for about $150. It took me a couple of evenings after work to get it replaced. After I got the new one in place and fired up the jeep the pressure was better when the engine was cold. But, as soon as I went for a drive, the pressure went back down when it warmed up.

This only leaves me knowing that I have a worn engine. I put some heavier oil in it, and now I'm going to just drive it until it gives out. Hopefully, you will have better luck thank me.
J-No,

When I thought my engine had gone south, I dropped the pan, and bought a stick of 'Plasti-Gauge". It looks like a thin green spaghetti. Its easy to use, cut a short piece, 1/4 inch long and place it between the crank and rod/main bearing and bolt/torque, then remove the cap. You compare the width of the squeezed Plasti-Gauge to the chart and it will tell you the bearing clearance. If all your rod and main bearings are within tolerance, no greater than .002 gap, you need to look elsewhere. You can buy .001 and .002 rod bearings if necessary. Probably not the cam bearings, oil pressure relief maybe? Don't streach the oil pressure releif spring to increase pressure! I replaced my pump with a high output pump which supplies a greater volume of oil for my old engine. At 220,000 miles I have good pressure at a stop light after a long drive on the highway.
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Old 05-22-2012, 06:45 PM   #13
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I just bought a 2000 and my pressure guage will start around 20 when i crank it up and run between 40 and 60 on the highway and go back down when i decelerate. the mechanic at the shop told me it was the pressure sending unit, however my concern is that it could actually be something else? Has anyone had issues with it being a deeper problem than just the sending unit? I would hate to burn up the engine with too low pressure or blow it up with too high. Help?
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Old 05-22-2012, 07:33 PM   #14
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Quote:
Originally Posted by abaldwin View Post
I just bought a 2000 and my pressure guage will start around 20 when i crank it up and run between 40 and 60 on the highway and go back down when i decelerate. the mechanic at the shop told me it was the pressure sending unit, however my concern is that it could actually be something else? Has anyone had issues with it being a deeper problem than just the sending unit? I would hate to burn up the engine with too low pressure or blow it up with too high. Help?
Your mechanic is an idiot for telling you that. In reality, oil pressure is absolutely supposed to vary up and down in step with engine rpms. 20 psi at idle is very good, and heading up to 40-60 when accelerating is excellent, and the pressure dropping back down as the RPMs drop is 100% normal and to be expected too.

Your oil pressure is generated by a mechanical oil pump which spins faster and slower as the engine revs faster and slower. So naturally the oil pressure will go up and down in sync with the engine RPMs.

That the oil pressure does go up and down was unnecessarily alarming people who were new to "real" oil pressure gauges so the dealers were getting a lot of unnecessary complaints by people who didn't believe the dealer when they told them it was normal. So the dealers made the factory dumb the oil pressure gauge down in later model TJs so it only registers mid-scale so long as there is oil pressure. Dumb, that is not what oil pressure really does. That change happened around 2003 so your 2000 TJ is one of the fortunate models that show the real oil pressure.

So relax, your oil pressure is fine and you now know oil pressure is supposed to vary up and down in sync with the engine RPMs.
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Old 05-22-2012, 08:45 PM   #15
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Thanks, that's interesting and good to know
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Old 05-22-2012, 08:46 PM   #16
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Quote:
Originally Posted by Jerry Bransford View Post
Your mechanic is an idiot for telling you that. In reality, oil pressure is absolutely supposed to vary up and down in step with engine rpms. 20 psi at idle is very good, and heading up to 40-60 when accelerating is excellent, and the pressure dropping back down as the RPMs drop is 100% normal and to be expected too.

Your oil pressure is generated by a mechanical oil pump which spins faster and slower as the engine revs faster and slower. So naturally the oil pressure will go up and down in sync with the engine RPMs.

That the oil pressure does go up and down was unnecessarily alarming people who were new to "real" oil pressure gauges so the dealers were getting a lot of unnecessary complaints by people who didn't believe the dealer when they told them it was normal. So the dealers made the factory dumb the oil pressure gauge down in later model TJs so it only registers mid-scale so long as there is oil pressure. Dumb, that is not what oil pressure really does. That change happened around 2003 so your 2000 TJ is one of the fortunate models that show the real oil pressure.

So relax, your oil pressure is fine and you now know oil pressure is supposed to vary up and down in sync with the engine RPMs.

well said
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Old 09-17-2012, 03:16 PM   #17
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Reviving the oil pressure question....

Wife has a 2000 TJ 4.0L...from reading this thread it has the 'real' oil pressure gauge in it. However, the gauge has always read around 40. Now when we drive it, under acceleration, it sits at 80. Deceleration, it slowly drops back to 40, then any acceleration again it steady climbs to 80.

Sounds like the oil pressure sending unit going on the fritz? Is there a way you can isolate it to test that? Don't have any manual gauges lying around to test the gauge itself.

Thanks for the help!
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Old 09-18-2012, 07:58 AM   #18
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Originally Posted by Hubdeep View Post
Reviving the oil pressure question....

Wife has a 2000 TJ 4.0L...from reading this thread it has the 'real' oil pressure gauge in it. However, the gauge has always read around 40. Now when we drive it, under acceleration, it sits at 80. Deceleration, it slowly drops back to 40, then any acceleration again it steady climbs to 80.

Sounds like the oil pressure sending unit going on the fritz? Is there a way you can isolate it to test that? Don't have any manual gauges lying around to test the gauge itself.

Thanks for the help!
The oil pressure senders usually fail to the low side and not high side of things.

It sounds llike the oil pressure releif maybe stuck closed. The oil pressure releif is a plunger with a calibrated spring behind it. When the oil pressure gets to a preset the spring allows the plunger to move forward and dump excess oil back into the pan reducing the volume of oil and keeping the pressure down.

The oil pressure releif is in the oil pump, drop the cross member, disconnect the exhaust from the header, pull the pan. buy a new pump and install. I have had my pan off 3 times and never had to replace the gasket.
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Old 09-18-2012, 08:20 AM   #19
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I agree. I've had many non-OEM junk sensors. One sprung an oil leak within 6 months.

Quote:
Originally Posted by Jerry Bransford View Post
...So the dealers made the factory dumb the oil pressure gauge down in later model TJs so it only registers mid-scale so long as there is oil pressure...
LOL, yeah, I got one of those on my truck. And an OP warning light, too. The factory gauge is just for looks.
With this kind of dumbed down gauge thing and the "my accelerator is stuck and I don't know what to do!" and the "you can really downshift an automatic in the mountains?" people are getting less and less competent and safe to operate a motor vehicle, IMO.
I don't expect eveyone to be a mechanic, but I wish there was some basic mechanical/functional/emergency driving knowledge about how to work a car and what is normal required to get a driver's license.
My 2 cents.
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Old 09-18-2012, 08:57 AM   #20
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hubdeep...Jason, right? this is Jay from the Creepers board & was out with you guys on saturday @ rausch.

mine was doing the same thing in my 99. i ended up replacing the switch & now everything is fine. i'm not sure if that was definitely the problem. but it stopped reading high after i replaced it.
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Old 11-26-2013, 06:40 PM   #21
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i wish i could have any update bout the OEM or the aftermarket one.....
who have better result with the aftermarket or the OEM,?
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Old 11-26-2013, 06:42 PM   #22
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Quote:
Originally Posted by MountainRoad View Post
Alright, I bought a '99 TJ in november of 2011. Enjoying it very much. Wish warm weather would get here just had a few teases so far.

The problem. I noticed yesterday at a stop light my check gauges light was on. So I checked the gauges only to discover in horror that my oil pressure gauge was at zero. .

So i immediately shut off engine. I got out and looked under jeep expecting to see oil everywhere but it was dry. I got back in and started the jeep (pressure was back up some still not normal) and pulled off the road.

I had just checked the oil level before I left home. I checked it again. OK fine. I checked the radiator fluid for signs oil was leaking into it. Fluid looked good. I started the engine and the gauge was not reading zero but hovering just above maybe about 8 or 10 psi. I revved the engine and the gauge climbed up near 40. Usually it reads about 37ish at idle and 44ish at highway warm.

I let it idle again and it settled on about 8 or 10 again. I got out to listen to the engine. sounded fine. completely normal. engine temp was fine too. I decided to take it home and get on the net.

So here I am. I've read about the sending unit going bad and thinking of replacing it. Autozone has it for about $44.00 - dealer $66.00. Which one should I get. Will the OEM work any better or last longer? Is it worth it?

Also if it was reading zero but running fine surely that means that the sending unit is the culprit right? It wouldn't run fine, sound fine, at zero? It scared the crap out of me. Could it be the oil pump?

What if i replace the sending unit and the new one does the same thing? I don't have a pressure gauge to hook up to it. They run about $60.00. Does Autozone (or someone else) lend one?

BTW I changed the oil about 1500 miles ago to full synthetic. Could this be part of it?

Thoughts, ideas, concerns all appreciated - thanks
MR......
i have the same problem with my 2002 TJ.. so which one did u choose?

Aftermarket or OEM sending Unit?
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Old 11-26-2013, 07:08 PM   #23
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I would go OEM> For the few extra bucks, you will be getting a lot more quality. Look how long the original one lasted. IMHO
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Old 11-27-2013, 01:43 PM   #24
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I would go OEM> For the few extra bucks, you will be getting a lot more quality. Look how long the original one lasted. IMHO

Thx; very realistic

will do
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Old 12-10-2013, 02:58 PM   #25
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Help Help.... i did change mine but it works on and off.... what next now?

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