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Is 80 (max on gague) a high oil pressure reading for a '96 XJ 4.0?

B

bradleyheathhays

NAXJA Forum User
Location
Lexington, KY
Long as I've owned this 4.0 I've never really paid attention to the oil pressure gague. So whatever it's normal operating psi is I just don't know. Recently I noticed when pulling a moderately heavy empty single axle trailer I was showing 80 (max) on oil pressure all of the time. I thought that might be because of all the extra weight. But after observing my oil psi without the trailer I"m not so sure. Afterwards, during a very easy acceleration up to 60 mph without the trailer the oil pressure maintained at least 80 (max) and often moved above the gague's limit to around 90. Did notice it slipped down to around 60 for a bit but that was only during coasting and braking. In general, my oil psi is pegged close to 80 almost all of the time.

Is this normal?
 
Oil gauges are hit and miss sometimes. Anytime my 92 4.0 would peg out at 80 I never really got worried. 60 psi was normal for mine and every now and then get to 80 randomly. But now that I swapped to a 5 speed and had to change the oil pressure sensor I don't think it has ever been to 80 since then :)
 
Your sensor could be intermittently failing. I know on the newer ones that when the gauge fails, it will peg out. They are not very expensive to replace.
 
Are you running a Fram filter?
 
I think your gauge being shot is more likely than your 4.0 pegging 80+psi at any time.
Put a mechanical gauge on it and see.
No, 80 psi isn't normal. Even 60 is high on a 4.0
 
yossarian19 said:
I think your gauge being shot is more likely than your 4.0 pegging 80+psi at any time.
Put a mechanical gauge on it and see.
No, 80 psi isn't normal. Even 60 is high on a 4.0
Click to expand...

i get between 65-75 psi under acceleration. but once crusing it drops to about 40-60 psi depending on speed.
 
I'm legitimately happy for you.
I cruise at 40, get to 60 under acceleration (now that I think about it) and have a hot idle around 10-15.
Pegging the gauge, I maintain, is more likely an electric issue than honest pressure.
 
Mine runs about 55-60 at cruise, about 20 when totally warmed up.

In hind sight, I changed the sender, then the filter. I now think it was a sender issue vs a filter pegging the gauge. Tayln made me rethink my thought process.Got to focus on scientific thought:)
 
I thought I had freaky high oil pressure for couple of years until i noticed that i had 40 with the motor not running. Replaced the sending unit. 0 with not running. Normal to low now running.
 
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