oil pressure Q's

hey guys, got a question about oil pressure.

history was a cracked head ('00 XJ 4.0L auto) at 164,000 kms ... replaced that with a '93HO head, kept the '00 intake and added a SS '93 exhaust. Anyway on to the heart of the question ... I hit about 3.5-4BAR at cold start, and the guage doesn't dip below 1.5BAR until it's run for a few hours ... on the road it climbs back up to 3Bar at 2000rpm and will go to 4Bar when just warmed but stay's at 3Bar after it's run for a few hours. At idle after running for a while the needle will dip to .75-1Bar but climbs back to 2-3Bar when driving.
there is also a slight very quiet tapping at all times since before the head issue which I assumed to be a minor pistion slap as every jeep engine (2.5L and 4.0L) I ever heard eventually makes it. it hasn't gotten worse since the head swap.

could this be oil pressure issue be damage from coolant in the oil pan (there was never any vissible mixing in the pan that I ever saw ... no milkshakes here. But even a small amount mixing can cause damage from what I understand.
Or ... am I just being paranoid and it's just another JEEP 4.0L with 175,000 kms.
There are no oil leaks as I fixed the usual oil filter adapter issue with the head swap.

Damn you Canadians and your metric system! lol.

The characteristics of your oil pressure seems normal for last gen XJs (97-01) from what's been posted here.

I.E., http://www.naxja.org/forum/showthread.php?t=1005688

However, given that...assuming 1 Bar = ~14.5 psi...your idle pressure after running a while seems a little low...0.75Bar * 14.5 = ~10.8psi.

I'm guessing that you are reading from the dash gauge? If so, it has been posted here that those gauges are notoriously inaccurate. Best to use a mechanical gauge.

And if not asked already...what oil filter are you using...the Fram brand and copies seem to cause the oil pressure to be a couple psi lower (vs. using another brand of oil filter).

yeah 1 Bar = 14.7psi ... if i could swap the guage out I would ... I go back to before the metric system so I just as confused sometimes. Not to mention most industry here still yaks psi not Bar and Kpa.

anywho ... normally I use a Ford FL-1A (generally a synthetic media purolator pure one) but recently I had to toss a Fram tough guard PH-8a on (I stopped using the midget filter years ago - yes I cross referenced the filters with a secret decoder book I snagged from a mechanic buddy of mine - an oil filter crossover manual). It adds an extra 1/2L or so to the oil capacity and doubles the filtering capability. But either way the issue was there prior to the crap filter.
Yes, that's the dash guage I'm going off ... maybe I'll try a mech guage in the engine bay then.
Also of note I use 2L of Synthetic and the remainder is traditional oil on all changes with a 1L bargain brand oil to flush with prior to filling if that's of any consequence.

And one further detail ... the engine still pulls strong ... real strong, as in the new (older) head really woke the beast up. I guess the larger intake and exhaust ports really do make a big difference. but that's another thread.

Yeah, I'm using the 80's 5.0L mustang filter on mine...adds about 1/2 quart capacity.

Well, according to specs that's been posted here...the min pressure at idle is around 13 psi which is about 0.88 Bar.

So, I'm thinking that your pressure is okay and that the dash gauge is not accurate.

Also, forgot to mention...if you are running 5w-30...you might try 10w-30/40...some of us like me run the 15w-40 oil. I don't think it will do any harm or good, but if it causes your oil readings to be just a little higher...it is a psychological thing, I guess.

My 2000 (with a cracked head) runs high oil pressure. When cold, it almost maxes out the gage, and never gets below 25 at hot idle. Maybe by oil pressure relief valve is clogged up with water/coolant slush. Hopefully I'll get my 97 head on soon. Mine also makes a lot of piston (or something) clatter. 110k miles,

Devil, the numbers you mention are identical to what my 98 runs: 0.75 Bar at hot idle and 3 Bar at 2k RPM. No issues here. I think you are being paranoid. I also notice that certain oils will make the pressure higher or lower depending on the viscosity.