High oil pressure at start?

Qban

New member
I'm still looking for overheating gremlins in my engine after I recently replaced the exhaust manifold which had a big crack near to collector.

One thing I noticed is that my oil pressure seemed a bit high. When the engine is warm and I start it up I get about 40 psi, every 30sec or so my idle sounds just a tad different and my oil pressure psi dips to 28 psi then sits there for a bit before slowly going back to 40.

Is this "bouncing" oil pressure psi normal, could it be a clogged oil passage or something else. I'm running rotella 10w30 and a wix filter.

Thanks for your help.
 

Digger87xj

New member
40 is not high, or low, for that matter.

Pressure drop with associated idle fluctuation could be a failing hydraulic lifter, but hard to say over the interwebs.
 

Tim_MN

Freakish Hand Strength
NAXJA Member
Engine rpm's makes the oil pressure vary. Cold oil generates higher oil pressures than warm oil. You should be comparing warmed up oil pressures. Normal oil pressure is 10-15 psi at warm idle, and 35+ psi at 55mph.

All of 5 my XJ's have/had about 40-45 psi at 55 mph.
 

thatxjguy

New member
When you first start your Jeep, your oil is very thick, so it is normal for oil pressure to be high. As it warms up, the oil thins. This is what the ratings, such as 10w30, mean. It has to do with the viscosity at different temperatures.

When your oil thins out after being warmed up, your oil pressure should be around 13 PSI or more. When you're cruising through different RPMs, it is normal for your oil pressure to rise, as your oil pump is sending oil down the journals of your moving crankshaft to lubricate your bearings in volume.

There is nothing wrong with high oil pressure, but yours is definitely not high. It's also not low.
 

Johnnie Walker

Piece of Fish!
NAXJA Member
When you first start your Jeep, your oil is very thick, so it is normal for oil pressure to be high. As it warms up, the oil thins. This is what the ratings, such as 10w30, mean. It has to do with the viscosity at different temperatures.

When your oil thins out after being warmed up, your oil pressure should be around 13 PSI or more. When you're cruising through different RPMs, it is normal for your oil pressure to rise, as your oil pump is sending oil down the journals of your moving crankshaft to lubricate your bearings in volume.

There is nothing wrong with high oil pressure, but yours is definitely not high. It's also not low.
Actually, most modern oils the (10w30, etc) does not mean much. It is just a number. With this most oils are about "200" +/- weight cold, and at NOT typically ~10 weight.
I would buy/rent a manual oil pressure gauge and confirm your oil pressure.
 

thatxjguy

New member
Actually, most modern oils the (10w30, etc) does not mean much. It is just a number. With this most oils are about "200" +/- weight cold, and at NOT typically ~10 weight.
I would buy/rent a manual oil pressure gauge and confirm your oil pressure.
I don't buy that. Stringent specifications are necessary and manufacturer marked for a reason.
 

Qban

New member
The engine was warmed up and at idle with 40 psi. That's what had me concerned. The fluctuation seems weird to me as well...
 

winterbeater

New member
Standard gage doesn't mean much. Key in run position, but engine not started, mine had 30 or 40PSI. I replaced the sending unit. Lost 30PSI at hot idle. LOL.
 
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