XJ oil Pressure

coreys · May 30, 2006

I have a 88 XJ 4.0 4x4 with 213,000 miles. What is the normal oil pressure at idle after the engine has warmed up? The engine runs great, but I have noticed my oil pressure dropping around 20 psi at idle. Is this normal?

scca28 · May 30, 2006

I know everyone says not to rely on the stock dash gauge,
but if that is what you are going by, my '88 4.0 runs a little above the 20 mark when warm, in gear with brakes on. That's at 124k with a new oil pump and rod bearings. Actually, it ran at the same reading before all that work....

XJ Jeepin Girl · May 30, 2006

scca28 said:
I know everyone says not to rely on the stock dash gauge,
but if that is what you are going by, my '88 4.0 runs a little above the 20 mark when warm, in gear with brakes on. That's at 124k with a new oil pump and rod bearings. Actually, it ran at the same reading before all that work....

You have an '88 with 124k? Tell me you rebuilt the engine, right? Wowza.

Anyway, I think he's right. The dash gauge is crap, at least it is in my 96. My oil pressure varried from 20-60 this weekend, but I'd say it is usually around 40?

johnlv6 · May 30, 2006

I think that's normal. Mine drops to around 20 at idle. By the time the engine reaches 1,400 rpm or so it's back to 40 psi. My 4.0 has 156,000...it's a strong running motor though.

40 psi is the norm for me though.

97cntryxj · May 30, 2006

Not trying to hijack this thread or anything but in the last week my (97 xj 152000mi) the oil pressure guage has been reading around 10 psi at idle (it never used to be this low), and if i raise the rpms the oil pressure reading goes up and will run around 40 while im cruiseing along, i replaced the oil pressure sending unit about a year ago. has this happend to anyone else and was it just the guage/sending unit or oil pump/ bearings???

87manche · May 30, 2006

Spec for the 4.0 is 17 PSI at operating temp, Idle RPMS.
37 PSI for operating temp off idle RPMS.

Dr. Dyno · May 30, 2006

coreys said:
I have a 88 XJ 4.0 4x4 with 213,000 miles. What is the normal oil pressure at idle after the engine has warmed up? The engine runs great, but I have noticed my oil pressure dropping around 20 psi at idle. Is this normal?

That's normal.

Not trying to hijack this thread or anything but in the last week my (97 xj 152000mi) the oil pressure guage has been reading around 10 psi at idle (it never used to be this low), and if i raise the rpms the oil pressure reading goes up and will run around 40 while im cruiseing along,

10psi at idle definitely isn't normal (minimum should be 13psi) and points to worn rod/main bearings.

OR2000XJ · May 30, 2006

I have a similar "problem" on this thread: http://www.naxja.org/forum/showthread.php?t=85004

I know that my idle at 20 is a new thing for my 80,000 mile 2000XJ. I run at about 40-45 normally, but it has been spiking a bit higher lately. I get up near 70 at times, and I have no clue why. Engine runs great, and I follow all checkups and LOF times. As my DD it confuses me when something like this happens--it really catches my attention!

BillyBob · May 30, 2006

As per the 89 FSM: "At Idle Speed (600rpm) 13psi, At 1600+ rpm 37-75psi"

scca28 · May 31, 2006

XJ Jeepin Girl said:
You have an '88 with 124k? Tell me you rebuilt the engine, right? Wowza.

Not rebuilt yet...But I think it's coming. I had the bottem open for a little knocking noise and the usual leaking rear seal. Seal job went okay, no loose bolts on the T-C, had a set of rod bearing and popped them in. The old ones weren't that bad. Didn't pull main bearings other than the rear one. New oil pump even though the old one looked great inside. But like I said,the oil pressure ran the same before and after. Only problem I ever had was an intermittant pegged needle which was cured with a new sender.

XJ oil Pressure

coreys

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scca28

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XJ Jeepin Girl

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johnlv6

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97cntryxj

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87manche

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Dr. Dyno

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OR2000XJ

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BillyBob

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scca28

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