Hey guys, I just got done after about 9 hours spread over 4 days...swapping my cracked 0331 head to an 0630 on my new 01 xj. Taking baby steps here! Here's my next headscratcher. At cold idle, at the guage, my oil pressure rides around 40psi, at warm/hot idle right around 10psi (first tick mark) on acceleration, it bumps itself up to 30-40psi depending on engine load. My 89 xj rides between 30-40 no matter the condition. I'm leaning toward the pressure sender being bad, but i'm not 100% on this one. I've only ever seen the extremes with them being good, or bad. Any help here would be appreciated

 

Mine is exactly the same way. I think we are okay.

 

You're fine. You can always verify with a mechanical gauge if you want a more accurate reading of your oil pressure.

 

Honestly? It's too low. Just because 100 people say its normal because their old jeep is the same way, doesn't mean its true.

Mine was that way. I replaced the oil pressure switch. Takes 5 mins. No special tool. It's next to the dist cap. Once I replaced mine. It returned to normal. 60psi on warm up. Once warm its 50psi.

My vote? Replace sensor!

Pics below are from my YJ and now my XJ. 105* outside. Trip around town before photo. Your sensor is bad, or oil pump. Don't trust my photo? Call a shop. Tell them your driving around with 10psi on oil. Tell me what they say. lol

 

You idle at 50 or 60 psi? Sounds like your gauge is further off than the OP

 

My Suburban and truck are off too then I guess. Not to mention, my old YJ was off too. What are the odds all my vehicles I own are off? lol

Anyway, OP, anything under I think 20psi (iirc) you should be concerned.

UPDATE: I didnt' verify. But after google search it states the manual says 20psi at idle is the minimum. 40-60psi while driving is the avg.

 

Mine hot idles at a little over 40 so his cant be far off

 

Minimum factory spec is 13 PSI at idle.

OP, what brand of oil filter are you using?

 

Plain and simple your bearings are worn due to the cracked head contaminating the oil. What can you do about it? NOTHING unless you want to rebuild. Just to make you feel better I have the same problem but worse (4 psi at idle and 20 psi at cruise) and have driving it like that for a long time. She is my very busy daily driver with a combination of stop and go city and long range highway miles. IMO don't freak out, when things gets critical your engine will warn you with noise before the catastrophic happens. If you are getting oil to the rockers your good.

 

Amazing!

 

I was getting 10 psi at hot idle, put in a new pressure sensor and now get 20psi at hot idle, 50 psi at cold start, 40-45 psi while above 1600 rpms. I haven't verified these numbers with a mechanical gauge, but consider I wasn't getting much noise out of the engine and it had good pickup, I felt like these numbers were more accurate. Plus, my old gauge looked like the original, and would get worse readings the longer I drove.

Oil pressure sending units are pretty cheap, 20$ off rockauto, only about 38$ if you get a Mopar one somewhere. In theory they don't take long to replace, mine was rusted on a bit but I eventually got it off with some vice grips.

 

Don't fool yourself with the dash gauge it is meaningless....use a good mechanical gauge. I use a mechanics diagnostic gauge.

 

It's true, a mechanical gauge is the only way to be reasonably sure of the what the true oil pressure is.

 

Got a write up to install a new autometer gauge to replace the crap dash one??

 

Agreed with these guys up there ^^^

1. Verify pressure with a mechanical gauge
2. If wrong, replace sending unit
3. If still low, replace filter
4. If still low, there is a high likelihood that coolant ate your bearings before you replaced the cracked head. You can live with it or do a rebuild. If it doesn't drive too bad and you aren't racing, heavy towing, or putting a ton of load on it I'd probably hold off on the rebuild until something else gave out.