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Discussion Starter · #1 ·
I’ve been wondering about this for a while. I feel my oil pressure is low after warm up. The picture is idling after a good long warm up period. Should I be worried? It’s running 10 PSI per 1000 RPM.



Thanks.



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1) What weight oil are you running?
2) How long (miles and time) since your last oil change?
3) What does the oil pressure gauge read at highway speeds?
4) What does the oil look like on the dipstick? (amber, kinda dirty or black)?
5) Do you run any additives in the motor oil?
6) How many miles on the motor?

Good Luck, L.M.
 

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Discussion Starter · #3 ·
I’m running 10w-30 that was changed last August. The oil only has around 1000 miles on it, as I rarely drive the Jeep. It’s a weekend toy. The oil is still Chrystal clear and clean, a little dirtier than out of the bottle. No additives in the oil.

The Jeep has 249,000 miles on it. I just did the water pump today and checked the timing chain to learn it has been recently replaced. I think this engine has had some work in its past as it has many new gaskets. I’ve had it for a year.

I changed the oil sending unit this time last year, as the pressure would go darn near to 0. It got better with the new unit. My next check will be a mechanical gauge.

It’s 59 degrees out here today. It runs about 20 PSI at driving speeds (45-55).

Thanks.




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Rule of thumb is 10 psi for every 1000 RPM as you mentioned. 45/55 at what RPM, barely turning in 5th or?? You could try a 5/40 or 10/40 oil and see if that helps out, sure cant hurt.You're at about 80% of a reasonable service life so you may have to live with what you have until you rebuild or replace.
 

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Well, you're nearing time for an engine rebuild, that is for sure. Like 8thtimer said, 10psi per 1000rpms is baseline minimum.

Do you have a lot of engine blow by?

Does it have any knock developing or excessive valve train noises?

If not, run it till one of the above starts then rebuild it.
 

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Rule of thumb is 10 psi for every 1000 RPM as you mentioned. 45/55 at what RPM, barely turning in 5th or?? You could try a 5/40 or 10/40 oil and see if that helps out, sure cant hurt.You're at about 80% of a reasonable service life so you may have to live with what you have until you rebuild or replace.
c5wagner;34632341 said:
Well, you're nearing time for an engine rebuild, that is for sure. Like 8thtimer said, 10psi per 1000rpms is baseline minimum.

Do you have a lot of engine blow by?

Does it have any knock developing or excessive valve train noises?

If not, run it till one of the above starts then rebuild it.
Quotes in red are kinda my sentiments too. 8thtimer suggests 5W-40 or 10W-40. Depending on how cold it gets where you live and if you keep your Jeep in a garage, you might consider 20W-50. If your jeep lives outside, you might consider an engine heater if it gets real cold and the 20W-50 helps with the oil pressure.

You state that your engine might have had some work in the past. Why not do a compression test and a leak down test. If both tests show a healthy engine, you might think about replacing the oil pump.

Good Luck, L.M.

P.S.
Cold weather, heavy oil (20W-50), the vehicle living outside, and infrequent use make for difficult cold starts. One thing I've learned through the years is an engine warmer and a battery tender are great assets in making cold weather starts a lot easier.
 

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Discussion Starter · #7 ·
Thanks for all of the suggestions. The Jeep is generally parked for the winter, but I may have to daily drive it soon for a few months. It sits inside now.

I’ll put in a thicker oil next oil change. Since we are entering our coldest time now, the 10w-30 should get me by. Once we get back above 32 for the norm, I’ll step it up and keep my eyes out for an engine.

The next oil change may involve dropping the pan and inspecting the bottom end. I’ll also do the compression and leak down tests.

Thanks!!!


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Your gauge or sensor could be dyslexic.
This is something to consider also. The one in my 91 is never consistently reading the same. Junky gauges/wiring, another jeep quirk for us to play with. Before doing anything serious Id get a good quality liquid filled gauge and stick it in the block and see what you get. If you're gonna drop the pan for a looksie, something like a Melling high volume oil pump wouldn't hurt. There pretty tough engines, but I did have one 4.0 XJ with lower pressure like you have and make no noise for whatever reason.Chit happens ya know.
 

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You can always put a mechanical gauge on a "T" fitting at the oil filter fitting.
You'll have to lift the hood to see the gauge, but you can get a better idea of the true oil pressure if you use a quality gauge.
With the gauge at the oil filter, you won't have to modify your dash to install a gauge that you'll only need to compare readings with your stock gauge that may or may not be "dyslexic".

Good Luck, L.M.
 
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