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Old 07-10-2010, 09:02 AM
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oil pump or engine swap?

New guy here with a couple questions, looking to tap in to the wisdom of the Forum. I have a '97 2.5 that I think the oil pump is going bad. Once it gets warmed up, like driving the freeway for a couple miles, and I stop at a light at idle, the oil pressure completely drops out on the gauge. I sit there in neutral and rev it up to hold pressure until light changes. As soon as I'm rolling again it creeps back up. First question is - Do you think it's the oil pump? Second question - Do you think I should swap out the 2.5 with 146,000 mile on it for a brand new 4.0, or just fix the oil press. problem? I have been given the 4.0 w/ tranny so that cost is covered(do need the computer,though). I have read some very mixed reviews about doing this swap. Most say I'd be better off selling my '97 and finding one with the 4.0 already in it. Has anyone out there done this swap?
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Old 07-10-2010, 09:56 AM   #2
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The oil sending unit is notorious for going out on Jeeps. I would look there before I tear out the engine. If you do choose the 4.0 route it is a lot of work from what I have read and yes you will need all the electrical.

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Old 07-10-2010, 09:59 AM   #3

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As long as you are happy with your Jeep, and no funny noise is coming from the motor, replace the oil pump
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Old 07-10-2010, 10:48 AM
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Ya, I know about the sending unit - replaced it when I bought the jeep a year ago. That fixed the problem at that time. I replaced it again since having this problem but it didn't fix it. I am happy with the jeep, just would like a little more power and concerned about it's future with 146k miles on it. The 4banger is limiting. I know I could regear it and feel a little better with it. I just didn't want to pass up a free brand new motor and tranny unless it's going to get too expensive and complicated to swap in.
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Old 07-10-2010, 11:31 AM   #5
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You'll also need the computer and wiring harness for the 4.0. Probably the radiator and shroud too.
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Old 07-10-2010, 01:17 PM   #6
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I have no idea how much work would be involved with the swap, but if you already have a brand new 4.0 and tranny, I would think the pro's would far out way the cons of doing the swap, as long as it is with in your ability to do.

Having the motor and tranny cuts out a huge amount of the expense of doing a swap and you know you will like more power and better driveability, who wouldn't. The mileage is not much different and i have to say personally i waited till I found a TJ with a 4.0 and I can say that i am very glad i didn't get a four gerbil TJ.
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Old 07-10-2010, 03:18 PM   #7
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I had the same problem. I decided to ignore it for a while because I figured adding oil every week would keep it running. The pressure was never good. Always either at 10 or 0. It could have been the pump or a clogged oil screen.Turns out my bears on the crankshaft were shot and replacing them was insanely expensive. But not as expensive as what happened next. I lost all my oil driving on the highway. I knew I was low but kept driving. My lifters were screaming and then BAM! I ended up spinning a rod bearing in the engine but was still able to drive home even with the jeep shaking like crazy on 5 cylinders. I ended having to do an engine swap anyway. My old one only had 80k on it. With a new core in, it drives like a power house. Great compression and power, oil pressure at 40-60. Even though it was pricey, it feels like a new Jeep.

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