Low Oil Pressure

[az chip]

gonna pick up a new sending unit tomorrow...ill post up my findings.

And they almost never do.

[memo43]

Wow the op last posted back in Nov 2012
I agree with you az chip what a tease
Now I know why we call it jeep porn

[1979bettywhite]

I'm having a similar issue, running ~30 psi cold, once warmed up I read 20ish unless idling in gear, then the gauge drops to zero, spiking occasionally. I have yet to check pressure with a mechanical gauge, and that sounds like a job for this weekend.

Well, just to keep the resurrected thread going, I have a somewhat similar issue with my 360 as the one mentioned above. Was going to post this today anyway, but figured since this post was up, would just stick it here.

Upon startup I get a little noise, sounds like it is coming from the bottom end. Takes a couple seconds before I get oil pressure. Shoots up to about 50-60 on startup. Once warm I get almost 0 at idle and probably 20-25 running. Using an aftermarket mechanical gauge.

Running 10w-40. Don't know much about the engine other than it is out of a 1990 GW with estimated 90k miles on it.

Would like to avoid a rebuild, but would also like to know I'm not damaging further. Thought about trying to run some 15w-40 and maybe a bottle of STP or Lucas.

In GA, so not too worried about low temps.

Any thoughts?

[tgreese]

15W40 would be fine in a warm climate. Not sure that STP will help much. Run a good oil filter like Wix (not Fram).

If you have zero pressure at hot idle, that's serious. The rule of thumb is a minimum 10 PSI for every 1000 RPM. So if you idle at 800 RPM, you should have detectable oil pressure of 8 psi or better.

These engines are known for having low hot idle oil pressure at high miles. The main source of the loss could be a worn-out oil pump. There's lots of info on how to refurbish the oil pump on the net. Unfortunately a lot of the threads that show you how to do this have been wiped out by PhotoBucket, so you will have to look around for pictures if you need that kind of help. The TSM describes how to measure the oil pump clearances to see if the pump is within spec. This can be done with the engine in the car.

You also could have bad bearings. Supposedly the cam bearings falling apart are one common source of low oil pressure. If this is the problem, the engine must come out for cam bearing replacement.

With such low oil pressure, you run the risk of rod bearing failure. The engine could run fine for a long time, or it could fail tomorrow. The oil film is all that keeps the crankshaft journal from contacting the connecting rod bearing metal, and maintaining that film depends on oil pressure. Once metal contacts metal at the rod bearing, the bearing fails quickly. When it happens, it will be loudly announced. Then it's time for a rebuild, or a new engine.

[1979bettywhite]

Thanks Tim. I just had a reputable shop replace the rear main seal due to a decent leak there. They do all the work for team WM here in the east.

Don't have a leak anymore. They had to do it twice to get it to stop leaking, for the most part. Said you would never stop the RMS leak 100%, but I would say it's 99% stopped now.

They said things looked good on the underside when they had the pan off. I guess I could get them to look at it again.

Hard to tell exactly what the mech gauge says at idle, but I don't have any noise at idle. Soon as I give it some throttle the needle comes back up and settles around 20-25 at speed.

[fulsizjeep]

Anyone ever read the TSM about this? The 77 TSM says 13# at warm idle is "normal" for AMC V8s. I always replace the sender first when I have doubts.

[tgreese]

Rear main seal has nothing to do with the oil pressure. They would have removed the rear main cap and seen the main bearing there, but that would not have told them much. The bearing could have looked fine. It's the low oil pressure that ruins the bearings, not the bearing wear that leads to low oil pressure.

If you think you might have some oil pressure at hot idle, I suggest you change to the 15W40 and a good filter, and a better oil pressure gauge. This is an excellent gauge - https://www.summitracing.com/parts/sww-82322/overview/ - I have also used this Summit gauge https://www.summitracing.com/parts/sum-g2934/overview/ which shows low pressures well.

If you want to do something that might matter, I suggest you measure the oil pump clearances. There is a procedure in the TSM. That would be a good place to start.

[tgreese]

I believe the 13 psi figure is what would trigger a warranty repair. The new engines I saw back in the day always had way more pressure than that.

[1979bettywhite]

Found this in my research. A good how-to for this item:

http://www.fourwheeler.com/how-to/engin ... -360ci-v8/

I see that BJ's carries it's own relocation kit as well now.

So I guess the first thing for me to do is check my gears and clearances in the current state? See if that is my issue to start?

I believe in reading this tutorial, it would not be too hard for me to do this job myself as a fairly new "mechanic of sorts"?

[az chip]

I am going through the oil pump repair right now. Having read as many threads as possible quite a large number of them start off, "I fixed my rear main seal, then the oil pressure was bad". My extrapolation from that is the oil pick up distance might not have been properly restored after having the pan off. But that is pure conjecture.

My end plate. Needs repair or the mid plate fix.

[1979bettywhite]

Thanks, I am going to take a look at it this weekend. Will go ahead and change the oil, may re-use the filter. It is a WIX and does not have many miles on it.

Guess the mid-plate fix would be the most simple and cheaper of the two options. But the relocation kit sounds nice. Higher volume after and easier access to the filter.

[az chip]

Found this in my research. A good how-to for this item:

http://www.fourwheeler.com/how-to/engin ... -360ci-v8/

I see that BJ's carries it's own relocation kit as well now.

So I guess the first thing for me to do is check my gears and clearances in the current state? See if that is my issue to start?

I believe in reading this tutorial, it would not be too hard for me to do this job myself as a fairly new "mechanic of sorts"?

Here is another thread on Jeepforum that explains a fix for the cover.
http://www.jeepforum.com/forum/f8/amc-v ... d-1050446/

[tgreese]

Thanks, I am going to take a look at it this weekend. Will go ahead and change the oil, may re-use the filter. It is a WIX and does not have many miles on it.

Guess the mid-plate fix would be the most simple and cheaper of the two options. But the relocation kit sounds nice. Higher volume after and easier access to the filter.

From what I've read, the gear end clearance has the most influence on oil pressure. It is possible that the gouges on the oil filter adapter could affect oil pressure, but I think how deep the gears sit into the housing has much more effect on OP. Thus the many tutorials on how to lap the timing cover to improve gear end clearance. The mid plate will not change the clearance unless you use a different thickness gasket. As the TSM shows, the gears are supposed to sit proud of the timing cover, and the thickness of the gasket provides just enough clearance for the oil filter adapter.

You don't need a filter relocation kit. The gear clearances are the critical issue. If correct gear clearances do not improve your oil pressure, then you have to suspect the cam bearings.

I installed the factory relocation kit in my 1973 CJ-5, in 1973. This was made from factory parts for a RHD Matador. On a CJ, the main issue was the front axle coming up and hitting the oil filter adapter. Later oil filter adapters were redesigned to provide more clearance. I don't think you have an interferance problem on a Wagoneer.

[tgreese]

Found this in my research. A good how-to for this item:

http://www.fourwheeler.com/how-to/engin ... -360ci-v8/

I see that BJ's carries it's own relocation kit as well now.

So I guess the first thing for me to do is check my gears and clearances in the current state? See if that is my issue to start?

I believe in reading this tutorial, it would not be too hard for me to do this job myself as a fairly new "mechanic of sorts"?

Here is another thread on Jeepforum that explains a fix for the cover.
http://www.jeepforum.com/forum/f8/amc-v ... d-1050446/

This is a good presentation - and the pictures are still there.

Shows that it's fairly easy to remove the gouges from the oil filter adapter. Lapping the timing cover is the big job.