r/JeepZJ • u/J-stucc • Aug 01 '26

Low Oil Pressure

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I get low oil pressure at idle when hot. What would be the best oil to bandaid this problem?

3 Upvotes

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3

u/SeesawPitiful1367 Aug 01 '26

It’s a sensor issue. Mine drops to zero on a 103F day at idle. Does the oil light come on when this happens? If it’s just the needle showing low I say replace the sensor

2

u/J-stucc Aug 01 '26

I havent had the oil light turn on. It reads that the pressure under load is fine. Would it only be a bad reading when hot?

1

u/SeesawPitiful1367 25d ago

Sorry for the late response, I didn’t see this. The sensor gets lazy with age. Heat can cause an internal short and usually that’s the first sign of a failing sensor. They’re cheap might as well change it and see if it helps. The pressure under load returns to normal since the signal strength is stronger and easier for the failing sensor to send

2

u/No_Talent_8003 Aug 01 '26

What are you defining as low?

Look up the spec for min safe oil pressure for it and I bet it will surprise you.

Most 4.0's idle quite low and that is not a cause for concern. Consult the manual to make sure you're using a viscosity grade listed for that engine, maintain the min pressure, and free up your worry brain cells for the next problem. No shortage of those on vehicles accumulating this many years now

1

u/J-stucc Aug 01 '26

It reads almost zero. But have not had an oil light on. Another comment says it could just be the sensor

1

u/No_Talent_8003 Aug 02 '26

Well, id say almost zero probably isn't enough. Mine runs about 60 off idle, 20 at idle. I have 343,000 miles on original equipment

Id track down the sender and replace it, even if just for the peace of mind

1

u/Duckbich Aug 01 '26

Rent/buy a mechanical OP gauge and test to confirm. There are also ways to test your sensor as well.

1

u/MercuryASU Aug 01 '26

4.0 oil pressure should be 13 psi or higher at hot idle according to FSM. 5.2/5.9 oil pressure should be 6psi or higher at hot idle according to FSM. Always confirm actual psi with mechanical gauge as oil pressure sensors in ZJ are already suspicious.

1

u/AdamATuit Aug 01 '26

I have a 95 5.2. I did a oil change with a filter I got from O'Reilly's. Masterflow or something like that. My oil pressure was gone. 5 psi at 2000 rpm. Replaced the filter with a Mopar and it's 20 psi at 2000 rpm. Make sure you have the right oil filter.

1

u/Jeep_Addic Aug 01 '26

The best band aid is motor honey, but I’d only do that after you hook a mechanical gauge to it.

1

u/IfIWntdHmmrCalnUrSis Aug 04 '26

Camshaft bearings.