troyflynn

Hey guys... I really need to reach out to a larger pool of ideas to help me solve this issue. My Jeep is a 2007 JK 3.8L, 2 door with 180k miles and is 100% stock, I purchased it with 30k miles in 09 and have always maintained it to a high standard. A few months ago, it started to ring the oil pressure alarm so fast that I could barely see what flashed on my dash. I thought it was due to low oil since my engine has always consumed oil between oil changes. Adding oil made the alarm go away. However, a few weeks ago, when the engine was warmed up after driving 5 to 10 miles, the alarm would come on when the engine was at very low RPMs and flash & ring on and off like it was barely being tripped. Being concerned that I had an oil pressure issue I stopped driving my jeep to work and started to diagnose the issue.

Step 1: I removed the oil pressure switch and attached an oil pressure tester gauge. Since it was a temporary gauge I could not close the hood and drive on the road. The results of stationæry testing with the oil pressure in my garage did not show any signs of low oil pressure at any RPM.

Step 2: The results of step 1 seem to point at a faulty oil pressure switch. I replaced the switch with an aftermarket switch but the issue quickly returned with the same symptoms.

Step 3: Since the switch seems to be fine, I decided to go after the wiring. The single wire going to the switch passes by a lot of edges and high-temperature areas. I decided to replace the wire from the switch to as far as I could access the wire on the front of the engine before it went under the intake. The same issue returned...

Step 4: Since my JK has 180,000 miles, I thought it would be wise to rebuild the oil pump and replace anything that was easily serviced during this repair. I replaced the following items: Complete Oil pump kit from Mellings, replaced the oil pick up tube and o-ring, oil pan gasket, front cover gasket, timing chain and gears, water pump, idler pulley, tensioner pulley, serpentine belt, spark plugs and wires, upper and lower radiator hose and thermostat, oil change with 5w-20 and new coolant. There was zero evidence of any metal in the oil. The same issue returned after 5 to 10 miles... really?

Step 5: Replaced the oil pressure switch with another brand new aftermarket switch and visually inspected the grounding strap from the frame to the engine for corrosion or damage. The same issue returned after 5 to 10 miles...

Step 6: I'm running out of ideas. My thought is to reattach the oil pressure tester gauge and see if there's any way to have my wife watch the gauge while I drive past the 5-10 mile point when I start to see this issue. I hope to be able to do that tonight.

Any help with this would be AWESOME!

Thanks
Troy

Jay2013jk

Welcome to JKF.. With all you have replaced the only item that comes to my mind is Engine Wear.. I do like the Step 6 before really leaning to Engine Wear.. Knowing the actual pressure with a gauge will be beneficial.. post up your findings. A good group of members here and not bashful with opinions and suggestions.

Skytow

Mechanical oil pressure gauge to find out where you really are. Man I hate electrical gremlins. Go drive it and get the oil hot with the mechanical gauge in line and see what you find.

Mr.T

Here's a link to installing an electronic oil pressure gauge on mine. I like it a lot, hate not being able to see oil pressure. A quick and dirty test could be tubing up a mechanical gauge held on by duct tape in front of the windshield. Also, there are oil filter adapter plates with a pressure port that are quicker than using a tee as in the link above.

Here's a quick test with no gauge, if low pressure indication only happens at hot idle after running at high throttle on the road: Put in a more viscous oil, or even a quart of Lucas. If the problem goes away, then it's probably worn bearings, a stuck oil pressure relief, a low pressure switch alarming too early, or similar non-electronic malfunction issues.

Having the problem after only 5-10 miles, but oil pressure looking good with a test gauge after a long time at hot idle does sound more like a wiring/electronic issue. What was the oil pressure at hot idle, and how long was it idling when reading the gauge?

Hate to say this, but when you had the oil pan off it was the ideal time to check and/or replace the con rod bearings.

Sixty4x4

Whose oil you using? Have you tried a high quality oil such as Pennzoil, Royal P or Amsoil? What about filter? I use Mobil1, Wix or NAPA Gold (same as Wix). Could be the bypass valve in the filter.

Mr.T

Troy, have you made any progress on this?

troyflynn

Thanks for checking in on me. We adopted a silver lab puppy last Friday and I’ve been following him around cleaning up messes! So, not a lot of time to wrench! Tonight I finally got back in the shop. Based on the feedback above, I decided to go ahead and replace the rod and main bearings. I pulled the oil pan tonight and tomorrow I’ll start rolling them in. I’ll post my results.

Thanks again for your suggestions.

Troy

rob_engineer

I had this low pressure on a CJ7. I "fixed" it by running a lower temperature thermostat and using 4 quarts of 30 wt oil + one quart of motor honey. I ran it for a couple of years like that.

troyflynn

Ok guys... here's an update:

I pulled the oil pan and intended to replace the rod and main bearings. I did replace all the rod bearings but I was intimidated by the rusty side bolts that hold the center mains in place. They screamed, "I'm going to snap!" So I let all the mains go. After I buttoned everything back up, my test drive showed no change to my oil pressure issue. Crap.

So this morning, I installed my oil pressure test gauge and had my wife watch it while I drove until the engine was hot. The gauge confirmed that the pressure drops at temperature and low idle to 4-5 psi. In fact, it stays around 10 psi cruising at 2,000 rpm.

Can worn main bearings affect the oil pressure this much?

I see two options going forward.

1. Replace the main bearings and pray the bolts don't snap. If they do... replace the engine.
2. Replace the engine now.

Unless there is something else to try. I may try oil additives but that seems like it's only delaying the inevitable path to a new engine.

Thanks!
Troy

troyflynn

I've always used high mileage Valvoline, Pennzoil or Castol GTX and standard or the fancy Fram oil filters. I've have this issue before and after replacing the oil filter.