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post #1 of (permalink) Old 01-13-2004, 03:12 PM
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99 tj 4.0 oil pressure

my 99 tj's 4.0l oil pressure gauge is acting funny. it goes to 40, then it will fluctuate between 45 and 50 at a constant speed, and when i idle it drops to about 25. is this normal?
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post #2 of (permalink) Old 01-13-2004, 03:19 PM
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Re: 99 tj 4.0 oil pressure

My 1998 4.0 runs about 40 lb. with rpm's, but drops to the 20-25 lb. range at idle. Thats with less than 28,000 miles on the engine. I bought the Jeep with 4,000 miles on it and it hasn't changed since then, so yours sounds to be o.k. to me.
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post #3 of (permalink) Old 01-13-2004, 06:54 PM
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Re: 99 tj 4.0 oil pressure

My 99 4.0 was around 42 at cold start 24 after warm up off idle or going down the road ..and 12-14 hot idle. I swapped in a high volume pump. It appears from some unofficial surveys ..that the "standard" oil pressure in the 4.0 varied quite a bit ..even within the model year.

The fluctuation is a bit odd ..you should be at your MAX pressure COLD at any decent road speed. Once warm ..it should be somewhat lower ..but just as stable and predictable. Your sensor may be faulty.
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post #4 of (permalink) Old 01-15-2004, 03:24 PM
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Re: 99 tj 4.0 oil pressure

sounds pretty normal.

type of oil you are running?
outside air temp? winter/summer?
engine temp?

any way my 98 4ltr runs at 40 to 45 at normal engine temp with 20/50 full sythentic in it, that is under acceleration. at idle and warm around 25.

Hope this helps.

post #5 of (permalink) Old 01-15-2004, 05:27 PM
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Re: 99 tj 4.0 oil pressure

Looks good to me. It moves around abit through out the day.
post #6 of (permalink) Old 01-15-2004, 06:12 PM
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Re: 99 tj 4.0 oil pressure

Mine is a 98, 4.0, D-44, 3in Rubicon Express, Discos, Detroit in the rear, custom bumpers, bobed front fenders, and CJ front turn signals.
post #7 of (permalink) Old 01-15-2004, 09:01 PM
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Re: 99 tj 4.0 oil pressure

thanks everybody for the help!
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