IGeeky1

Hello all! I'm the current owner of a 95 Wrangler and, as of a couple days ago, a 2001 Cherokee Sport.

Of course during test drives I saw nothing of warrant. Today I see oil pressure drop to nearly 0 at idle and I have read the huge range of possibilities that could be. I have not done enough testing at this point to talk in that arena. (fwiw sending unit appears to have been recently replaced)

While doing my research on this problem though I ran across something of interest. Somebody that by process of elimination pretty much figured it was his bearings and wanted to buy time simply used a heavier oil. This brought his pressure back up.

My question is this. By using the heavier oil and bringing the pressure back up, are you just making the gauge happy or are you really helping the vehicle limp along a bit further?

I guess the crux of my quandary is this. If using the thicker oil is helping to fill the bearing leaks and therefore helping oil to be properly distributed elsewhere, it seems good. After all liberal oil that is a bit too heavy for perfection is better than little to no perfect oil. The opposite thinking of mine says that the parts are getting a good lathering of the 10w30 oil then you are just making the gauge happy by using the heavier oil.

Anybody care to set me straight here?

Also found somebody that sort of did a flush with 1 qt oil and the rest kerosene. Ran at idle for a few minutes then replaced with proper oil and filter, Ran for a couple hundred then change oil and filter again. Sounded interesting to me. Thoughts for or against?

Thanks

Mark

Xj88

If your oil pressure goes up from simply adding heavier oil then you most likely have bearing issues. Id start by checking to make sure your sending unit is working properly. Verify your pressure with a mechanical gauge before you start dumping heavier oil in.

By the way. I enjoy your use of language.

cbush314

My 01 says it calls for 5w20. I figured since it was a high mileage engine that I would just run a little thicker oil in it, so I got some 10w30. Fired it up and let it run for ten minutes and it was ticking like crazy. I didn't know what the hell was going on. I called a local shop and they told me that use of specified oil weight was important and due to the limited clearance between the rockers and the valves, that thicker oil would cause a ticking noise. I changed the oil to the right weight and the noise went away after about 10 miles.

jbdpayne

x2 to xj88, the sending unit is pretty common to go, and its a quick fix if thats the issue, if not it could be the bearings but good luck to ya let us know how you make out man

IGeeky1

Thanks all.

XJ88, I see what you are saying with the heavier oil compensating for the wear "space" in bearings and giving a better pressure.

However, cbush13's post rather exemplifies the possible reason NOT to go heavier. If 10w30 is borderline too heavy, 10w40 may well be beyond happy. If so the pressure would look good but the oil isn't getting to where it needs to be.

If pressure is too low, 5w30 may not be being pushed to where it needs to be...

This is all hypothetical to me so I appreciate the voices of experience!

bigbadon

Your just making your gauge (and you) happy with thicker oil BUT your making your engine unhappy. Pressure is not a function it is an indicator of engine wear....repeat; Pressure is not a function it is an indicator of engine wear. All the pressure in the world will not eliminate worn bearings. Thicker oil will cause a restriction at the bearings that are not worn which will sacrifice them. Flow is what is important and believe or not, when pressure goes down,flow goes up. Bottom line there is nothing you can do for a tired engine except rebuild. I have been driving mine a very long time with only 4psi at idle and 20 at cruise.

Xj88

After some extensive searching and some reading over on bob the oil guy..
I will probably be going with rotella t6 5w40 in my jeep next change.

RTorrez1

The first question I have is. What brand of oil filter do you have? Assuming you have a 4.0 and you are talking about the XJ. Our 4.0's need a good quality oil filter such as Wix, Mopar or Napa Gold. If you have a Fram get rid of it. You may want to verify your oil pressure with a mechanical oil pressure gauge that you can rent at any auto parts store.

IGeeky1

Please share reasoning or link.

While looking for the post you may have seen I saw one from a biker that said while it starts out great it was pretty deteriorated after 2000 miles...bikes are likely different though.

IGeeky1

hmmm...you had me with you until this part. Set me straight if my mechanical knowledge is afoul here.

Oil pressure is the result of the oil pump trying to push oil from down low onto the moving stuff up above. The pumps flow is relative to rpm but for ease let's say @ 1000 rpm it pumps with sufficient force to push 10 oz of oil up the tube, against gravity and backpressure, and onto rockers etc.

I think it is easy to see that if the tube had a hole in it, say 1/4 of the way to the top (or in this case bearings the oil could push through), maybe now only 5 oz per minute will reach the rockers.

At some point the hole in the tube becomes large enough that all the oil can escape through it (path of least resistance) and none will make it to the desired rockers.

So while the oil pump may be having the easiest time of its life due to not having to push oil WAY up the tube (pressure down, flow up). The oil pump would now be pumping oil at its max potential (flow) and at maximum volume of oil (flow) our DESIRED flow has gone to Zilch. Or at least this is the way my head puts it together..
pressure down, flow up, while true, would be the sum of the desired flow of oil and the non-desired

Very curious though bigbadon, as a guess how many months/years is the "long time" that you 've been running at the 4psi idle and 20 psi cruise? Was your issue originally created by the infamous cylinder head crack or just many miles?

Thank

Mark

Xj88

Lots of opinions here.
Have fun:

http://www.bobistheoilguy.com/forums...2359446&page=3

djb383

Here are the facts about oil viscosity and the difference between pressure and lubrication.

http://www.supramania.com/aehaas/

IGeeky1

Purolator on their now, I intend on changin oil and putting a napa gold on...haven't decided on what oil yet...

First I wanna see if it has sludge in pan...maybe flush first? Anyone hear of the kerosene/oil thing I mentioned? I've heard pretty mixed opinions about seafoam to the point I don't feel warm and fuzzy there.

IGeeky1

Thanks for the link xj88 and djb383 !

djb383

It's always a good idea to have the goofy factory electric dash gauge readings verified with a known accurate mechanical test gauge.