Oil pressure falling

[Tombredone]

Ok,,, When I start up the oil pressures sits around 70,, as I drive along and the engine warms up, it drops. It usually will sit somewhere between 0-5... Its a brand new guage and sending unit,, It is an electrical guage, and it is on a 82-cj5 6 cycl... I know as the oil warms, that will cause it to lower some, but almost to 0,,,, any ideas..

Thanks
THomas

 

[Tug-n-pull]

My ol 79 258 starts out at about 55 PSI in the morning and after she warms up a bit drops to like 5 PSI now I use to really worrie about it but now I just let it run where it runs. Check the oil every other day or so as I do most of the fluids and just keep on truckin. If you find out why let me know too. tug

 

[redrooster]

Yep, it's definitely got a Jeep motor in it.
Do the sixes have the aluminum oil pump housing similar to the V-8?
That's normally where the V8 has the problem. The aluminum will get scored by dirt or whatever that isn't caught in the filter and the tolerances will get to great for the pump to work efficiently. That may be the problem on your six cyl. I just can't recall at the moment what the pump setup is like.
Putting 20w50 in there will bring the pressure up but may be harder to start if it's extremely cold.

 

[redrooster]

I heard it said somewhere on line the rule of thumb was 10 psi for every 1000 rpm. I don't like that scenario though. I prefer my oil pressure to sit on 20 psi or higher at idle.

 

[GreenReaper93]

My '93 does that all the time. The Stealership said that it's common and to just watch the guage every now and then. Normally I wouldn't trust 'em but a couple of friends work there. Don't know what else to say but the same thing Tug said. Good luck!

 

[Tug-n-pull]

Recently was told by a local ol school jeeper to run an A/C Delco oil filter and it would bring up the oil pressure. Not sure of there is any truth in this and or a reason for it to work. But the guy has a collection of old jeeps and they are all good running rides. If I have a question I can not get an answer for he is the man. Just thought I would throw that out for you. tug

 

[Tombredone]

Just seems the pressure dropping that much, and down to that little would mean an issue somewhere in there...

But I am learning as I go..

Thomas

 

[1981CJ5]

My '81 cj5 w/258 I6 oil pressure runs at around 55-60 at start up and then falls to around 20-25. It is pretty constant, thank god.

I am like Tug, but I check my oil everyday before I head home from work
just to be safe. Then again I do have a slight oil leak from somewhere.

I have read that if you do not have some type of oil leak then you do not have a jeep, is this true? I am beginning to believe it.

Joel

 

[redrooster]

That's so very true. A year ago I had no oil leaks. Now it leaks at the drain plug (easy fix) and at the front pinion seal and rear axle seal. I guess that's what you get for letting it sleep for weeks then taking it out and running the snot out of it for 2 days and putting it back up for weeks again.

 

[odjeep]

I tried the AC delco filter and it made no difference. Since then, when i last changed the oil, i decided to add Lucas engine oil stabilizer and, seeing as how its as thick as molasses, it raised my idle pressure from about 11 to low twenties. It seems to work fairly well and it doesnt start hard in the cold mornings as it would with 20w50 or even 10w40. Im currently running 10w30 and it starts and runs fine.

od

 

[redrooster]

Pressure is caused by resistance to flow. You can make even a worn out motor get oil pressure by adding thicker oil or possibly changing the filter (filter design may restrict flow). The problem is that you want the oil pump putting out the flow it was designed for so that it circulates through the engine properly.
I would guess that the problem is more than likely in the design or wear of the oil pump. It is very common on older Jeeps to run low oil pressure at idle.

 

[graewulf]

my guess is this is a high mileage motor... your oil pump is getting worn out.. if you drop the pan and install a new one, you should be able to get it back up to 30lb or so when its warm.... oil presure below about 15psi at idle is not very good... if I read you correctly, it does this while driving down the highway, this is very bad... it should not go below about 30 down the highway.

 

[mudbug]

Mine runs about 60psi when I start it when it warms up at idle it runs about 25-30 psi, at 55mph or above it runs 55psi, I always run a wix filter but I used a fram one time and I had a pressure of 10 psi so I switched the filter the next day and it went back to normal. P.S. I use a mechanical gauge, don't have much use for that electrical stuff.

 

[Sacredgroove]

hmmm at idle mine sits around 20,but when driving its up around 75-80....my gauge or sender may be shot though,they are original to my knowledge

 

[odjeep]

Is this oil pump wear thing common on most AMC 6's and 8's? I used to have a 79' CJ7 with a 360 that came from a 79' waggie which came from a 76' waggie and i never had any problems with it. It would start at 65, hot idle at 35-40, and run at like 50-55. It had a mechanical guage as with my wrangler. Is there an aftermarket out there that anybody has found that remedies the problem with the OEM pump? I have a new/slightly used pump that i took off of my last 258 which i had put in a few months before i overhauled it. Im trying to find time to put it in but if there is a far superior oil pump out there id like to put one of those in instead. Thanks for any help.

od

 

[graewulf]

oil pumps wear out, some faster than others.. i had a similar probem on a van i had.. once we replaced it, i did about 25psi at idle.

 

[Tombredone]

Re: Getting to know your peers

The pressure at idle is the same as traveling,, once it heads down,,, it only takes about 5 miles or so for it to head from 60 to 10 or lower. I am going to change the oil weight in it this weekend,, but sounds like by pump maybe bad?

 

[GreenReaper93]

My Jeep had a fairly new engine when I bought it (somewhere around 56,000). Thanks to a very generous wedding gift I was able to change mine out. Like Graewulf said, some simply wear out faster than others. Good Luck!