Oil pressure issues - JeepForum.com
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post #1 of 7 Old 08-14-2019, 01:14 PM Thread Starter
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Oil pressure issues

I just bought a 98 wrangler with the 2.5l. The guy said he put a used oil pump in it (Dumb) . It started dropping oil pressure so I put a new sending unit a new oil pump with new main and rod bearings. I installed everything last night and had good pressure, about 40 lbs. This morning after a 20 minute ride to work the oil pressure went back to 0. I dont know what else to do.???

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post #2 of 7 Old 08-15-2019, 10:46 AM
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The only way to know for sure what pressure you actually have is to put a manual gauge on it (for testing purposes). You can do that by removing the sending unit & attaching the gauge there. If you want to keep the gauge you can get a T fitting & have the sending unit & manual gauge too.

The pressure will always drop when it gets warmed up so that needs to be considered when checking it. At idle when hot it is likely to be 10 PSI or even a little less. 10 PSI per 1000 RPMs hot is plenty.

If you really do have 0 pressure you should hear the lifters clattering at idle. Given the things you have replaced I’m betting you have good pressure & probably a bad sender. Yes, even new ones are sometimes bad.
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post #3 of 7 Old 08-16-2019, 10:35 AM Thread Starter
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I went with the tee and put in the manual guage and kept the factory both read the same thing. Still 0 at operating temp. I was told there is a screen on the sending unit port and it is probably partially clogged. He said remove the 90 and remove the screen with a seal pick to clean it.
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post #4 of 7 Old 08-16-2019, 12:18 PM
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If it truly has 0 pressure with a mechanical gauge , might want to get your$back and buy a different Jeep.
Sounds like the seller knew it was having issues.

Get out and explore.
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post #5 of 7 Old 08-16-2019, 12:57 PM
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I am not aware of there being a screen in the oil galley at the sender but it would be easy to check.
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post #6 of 7 Old 08-16-2019, 01:02 PM
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ZERO pressure is automatically lifter clatter, at least. If it isn't doing that, then the pressure reading is wrong, and it isn't zero. I am not familiar with what could possibly block the pick-up channel to the sending units (when warm), but something in this is very odd.

Yes, the pressure drops as the oil thins when warming up, but there HAS to be some, or else things start to oil starve, heat up, and malfunction and you can hear that fairly quickly.

Excess clearances, wrong oil filter, worn pump gears, etc., all cause a pressure reduction, but some pressure should get to the gauge unless the passage gets blocked.

There may be a bypass circuit (where the oil flows without getting filtered), but as I recall, that should still read a pressure gradient at the sender.
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post #7 of 7 Old 08-16-2019, 07:19 PM
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Not that this is the case.. But if you want to TEST how the pump is doing and make sure nothing is stopped up. Pull the oil sender out of block and then pull the coil wiring harness so the engine dont crank up. if you have a T fitting you could put some hose on it to a bottle.. just a couple seconds is all you need to see a lot of oil.

Now turn over the engine.. oil will spray all over the place so have a rag ready..

there is no screen just so you know. I have build a LOT of these engines... a lot...
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