I entitled this thread "High Oil Pressure, Bad Cam Bearing" for the benefit of those searching the forum.

That said, I just confirmed I have a spun cam bearing.

Symptoms:

1. Valve train noisy,

2. Timing chain area noisy,

3. Thump type knock deep in the engine, which follows the throttle,

4. Low oil flow to rockers through the push rods,

5. Oil pressure follows the throttle, i.e., after starting the engine the oil pressure settles at 50 psi, but will slowly drop to 40 psi, then wander back to 50 psi, at random. When the throttle is advanced the oil pressure will follow steadily up to around 1900 RPM, then the oil pressure will zoom up to 75 psi (relief valve) then drop back to 60 psi. This is repeatable.

I hired one of the Chrysler/Jeep experts on "Just Answer" to analyze my symptoms ($18) and he confirmed it was a spun cam bearing. I asked him if there was a certain bearing that historically went bad. He said normally it is the front one he has found that has failed on the 4.0 engine but that he usually replaces all of them while he has the engine open.

I guess I need to open my motor up to see what's up. It's too bloody cold in my garage during the Michigan winters so I'll wait until spring.

Thoughts?

 

Do you have a diagram of the oil flow through a 4.0? It sounds like the #1 cam bearing bore feeds the lifters as well, the bearing spins and blocks the port, then starves the lifters. You want to look very carefully for a wiped lobe or two while you have it apart.

Either that or just slap a long block in it now before it gets really freaking cold.

 

I am having oil pressure issues as well the engine seems to be running fine, but the oil pressure meter has a mind of its own jumping around the place, but generally right off the reading as if extremely high. I have replaced the sender unit and this just reads off the chart high also, but does not jump around.?

 

If with the wire lead disconnected from the sending unit the gauge still goes full swing, the problem is with the wire itself grounding somewhere. (or you got the sending unit for the dash lamp & not the one for the gauge)

 

I replaced the sender unit that is located next to the oil filter, is there another one somewhere ?

 

Next to the oil filter is the correct location but Turbo is right. If you accidently got a sending unit for a light, it won't act correctly.
Mine would max out at 80 on start up, drop to 60 and sometimes as low as 40 after warm up and climb up to about 75 at highway speeds.
Put in a new sender and now, the readings are closer to what they should be and fluctuate very little.

 

A spun cam bearing should not block oil to other parts of engine. Check this http://www.jeepz.com/forum/attachmen...tion-chart.gif

 

Further progress on this issue.

Foolishly, I had forgotten my Root Cause Analysis training and jumped to conclusions. The first question in RCA is "What Changed".

Well, last September I replaced all the rocker arms because I had valve train chatter and when I pulled a rocker there was wear in the pivots, so much so that I could hook a finger nail on the edge of the wear. So I bought and installed a set of Sealed Power rockers from NAPA (this is what changed). Closed up the valve cover without checking oil flow to the rockers. I still had valve train chatter. I pulled the oil filler cap and looked at the only rocker visible with the engine running. There was very little oil flow at idle.

Yesterday I pulled the rocker cover and inspected the 'new' rockers and noticed that the oil hole in the rockers (at the push rod pivot point) was too small compared to the old rockers, and that the hole was not positioned like the OEM rockers. I reinstalled the old (worn) rockers and cranked it up. Got full flow oil at the rockers. See pic.



So, now back to NAPA to see if I can get my money back on these aftermarket POS rockers. Lesson: Use OEM rockers.

The oil pressure issue existed before changing the rockers.

I pulled up the '99 wiring diagram for the oil pressure sensor and noticed that the OPS ground is shared by the CC Speed sensor switches and they pass through the Clockspring. So, today while driving to Lowes the oil pressure started the bit about climbing to 80 psi around 1900-2000 RPM, so I turned the steering wheel back and forth while rolling and the oil pressure indication started to go up and down. WTF? Tried it with the cruise turned on and off, both. I was so interested in what was going on, I almost spilled my beer. This will need further troubleshooting with my VOM. I'm also going to see if a direct reading of the OP will show anything.

To be continued....

 

This has been the high point of my day. Thank you...

 

I believe that i have got the right oil pressure sender, its a valley forge unit. So i was reading about how the inline 6 in the early years was known to have a faulty oil pump after about 150,000 miles mine has only 135,000kms so how can i check my oil pumps working any ideas ? Thanks