1990 Jeep Cherokee Problem - JeepForum.com
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post #1 of 11 Old 05-13-2009, 10:48 PM Thread Starter
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1990 XJ Cherokee 
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1990 Jeep Cherokee Problem

So I am new to this forum, as you can tell by my posts. After all that aside, here is my problem.

I own a 1990 Jeep Cherokee. I've owned it for 1 1/2 years. It had given me some trouble, but we finally solved the problems. A couple weeks ago, my dad and I decided that we were going to replace the Oil Pump because my pressure was dropping.

So he ordered the part, we replaced it one day, put everything back together, and started the engine. A major oil leak occurred. We replaced the oil pan gasket with a rubber one, instead of the standard cork. It still leaked. So we took it in to a local garage where we get all out vehicles worked on. It ended up being the main seal for the engine, and after a $631 repair, it did not leak. So we were happy for a couple weeks. The oil pressure was staying up, we didn't have trouble starting, and the engine ran great. Well last Thursday, I started my engine to go to work, and I noticed the valves were tapping. I didn't think anything of it, because its always done that. The next day I get in, and the valves were louder. I was curious because it never did that before.

After a couple days of the valves getting louder, and no way to quiet them. It started tapping extremely loud. I would start it up, and it would rattle so loudly that you could hear it from inside the house. The valves would tap all the time. And when you accelerated, revved the engine, or just idol it would tap. But when the engine got over 2100 RPM's, it would be tapping loudly. I have no idea what is wrong with it. I read through my jeep book, and no answers on it.

Any help would be nice. I know I do not have much info on it, but its late, and I am tired. Thanks for everything.

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post #2 of 11 Old 05-14-2009, 06:28 AM
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Is the oil pressure still up? Have you checked the oil level?
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post #3 of 11 Old 05-14-2009, 06:30 AM
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Almost forgot, could be valve lifters need replacement. How old/miles/hard use does the engine have?
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post #4 of 11 Old 05-14-2009, 07:20 AM Thread Starter
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We replaced the oil last weekend. It was full and there was no sign of a leak.

And for the mileage, it has 135834 miles, and is not ran hard. I use it everyday, but I am easy on her.
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post #5 of 11 Old 05-14-2009, 10:09 AM
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Again, what is the oil pressure? Check the stick, don't assume you have five quarts.

Also, if you used a Fram - change it to any other quality filter. If the problem goes away, you just fixed it. Filters do fail and bypass oil, dropping pressure to zero. At one time Fram was known to use cardboard end caps on the filter media instead of crimping a metal cap.

The valves aren't tapping, it's the hydraulic lifters not receiving sufficient oil pressure. It's indicative of a bypassing oil filter, clogged oil pickup, sheared pump drive, or clogged lifter valley oil passage. As the dealer had the pan off for the rear main seal repair, it's possible some junk got into the oil and is stuck.

The cheapest, easiest thing to check is replace the filter first.
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post #6 of 11 Old 05-14-2009, 10:25 AM
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not to hijack...Fram does use cardboard in their filters thus the reason they are always free at the autostores LOL

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post #7 of 11 Old 05-14-2009, 02:18 PM Thread Starter
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When I would start up the vehicle, the pressure would go up to 40 PSI. It would stay up until the engine would heat up to 160 degrees. Then the pressure would drop to 10 PSI by the time it reached 210 Degrees. Then once I would stop, the pressure would almost be 0, hit the gas and it would go up to 10.
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post #8 of 11 Old 05-15-2009, 12:28 AM
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1989 XJ Cherokee 
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Sure its the lifters and not a rod knock?
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post #9 of 11 Old 05-15-2009, 12:53 AM
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either way i wouldn't run it too long with that low oil pressure.. i agree with these other guys on getting a new filter first.. TIRod knows what he's talking about.. its weird that you loose pressure as the engine warms? what viscosity oil do you use?
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post #10 of 11 Old 07-14-2009, 05:48 PM
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A buddy of mine had the same issue this weekend when we were out wheeling. Oil pressure started out high, then dropped to zero after being at operating temp for a few minutes. He let it sit for 10 minutes and it started up at normal pressure and again dropped after several minutes.

Any ideas?
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post #11 of 11 Old 07-14-2009, 07:33 PM
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It is normal for the pressure to drop when the engine reaches operating temperature. It is not normal for it to go to zero though. You also need 6 quarts of oil not five. I would rent/buy a manual oil pressure guage and install it to verify oil pressure.

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