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4.0 Problems and found solutions/suggestions for long life

10432 Views 121 Replies 33 Participants Last post by  bbusch
So with all the new 4 liter motor problems going on out there and with many of the problems being preventable I thought it would be a good idea to start a thread for others with lower mileage to possibly save their rigs motor before it dies on them at 120K or less. If anyone has suggestions as to how to prolong your motors life please chime in.. 8)

*Mods... may be a good idea to make this thread a sticky.

As for a trend I have noticed many of the older rigs (03-04) are starting to have cam and lifter problems at higher mileage (80 -120K mile range) and 05 to 06 models going out much sooner (some not even hitting 10k miles). It is my limited understanding that both year ranges could benefit from the use of a high flow oil pump (much like the Hesco unit that adds a spray line for the OPDG and cam) so that the cam and OPDG are properly lubed. Newer models may look at using the cam sync from an older model year if they also change over the sensor (if this can even be done) for a more reliable unit.
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Re: 4.0 Problems and found solutions

sorry post is acting up on the other screen so I am starting a new post...


Personally my Cam Sync recently started going out (the op drive gear is another story) and started making a churp noise that was extremely difficult to diagnose. If I could go back to 30K (or newer, 35K is where I think I started to notice problems) mileage I would have changed my oil pump to the Hesco unit and being mine is an 03 I am willing to bet it would be good to go to this day (not to mention years to come). Because I didn't diagnose that cam issue early on I ended up dumping money in here and there and now could have a nice sum to put down on a Hemi (thinking every time my engine would get better and I could keep all my extras like the OBA). It would have been nice for Jeep or one of the shops I frequent to have known about the issue and helped me through it from the start of notice but instead I learned the hard/expensive way.

I could keep going and may as this thread progresses but don't want to lose site of the threads point on prevention. So if anyone can help out with either their experiences or knowledge please chime in.

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As I'm on the third OPDG assembly now, thought I'd chime in with the very limited stuff I know or have found as of late.

A modification of some kind which is currently under review could/should be performed to the bushings/OPDG assembly to prolong it's life. This is currently under review and when a determination has been made as to the "best" way to handle this, I'll run it.

In the short term, it appears many folks have decided that higher ZDDP levels in the oil are necessary. Some folks don't mind adding a can of ZDDP additive so they do. Other folks-myself included-don't WANT to spend more money adding extra oil additives to the oil already in the engine. I have run Royal Purple exclusively since my original OPDG failure/recall issue at less than 1,000 miles on the clock. I ran 10w30 weight up until now. I recently sent an email to the folks at Royal Purple explaining my condition with the 4.0 engine and my two prior issues with the OPDG and wondered what their take on ZDDP levels was, how much I should run and if I should really add extra as an additive or not. I got an email back later that day stating that NO, I should not add extra additives to the oil, it was never a good idea to do that. They went on to say that the current oil weight I ran had a nominal ZDDP content of 1000 ppm and that the best thing for me to do in this 4.0 engine that they've seen good luck with was to switch to a slightly heavier weight oil in the 10w40 flavor which has a higher ZDDP content of 1300ppm and has shown to be enough for our engines. The slightly heavier oil has a higher allowed tolerance for ZDDP levels by the Feds so with this, no additive is necessary. Whether this is true or not for other brands, I don't know. I have since taken back the last 6 in the case and exchanged them for the heavier 10w40. Have NOT yet changed it as I'm not due yet, but will soon. Will report back if any noticeable change is deteremined when/if it occurs. Not sure how else to judge other than parts wear/failure.

I currently have an '05 LJ Rubi with 74K on the engine. Original full rebuild at less than 1000 miles, currently on 3rd OPDG assembly.

Look forward to others thoughts/opinions on how to prolong our engine life...

Best of Luck

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I have heard the same about using more ZDDP. 10W40 is good for warmer weather, but for colder weather I am considering Mobil 0W40 ACEA a3. My only concern is the rear main seal starting to leak again with the synthetic oil. That seal seems to be the weak point on the 4.0 engine for leaks.
Just an FYI... I started a case with Chrysler and will keep this thread updated with any info I can find out. Should hear back from them no later than Monday night. I will be interested to see how this goes as I am making no requests for warranty work (normally wouldn't waste my breath but would love to have an impact on this matter).
I suggest taking Valvoline up on its 300k engine warranty. Gotta change oil every 4k with Valvoline Syn., and keep records and register, but seems like cheap insurance for whatever comes down the line.
I'm going to keep an eye on this, my '05 recently hit 70k. I don't want it to blow up in my face.
[quote='05TJLWBRUBY]I currently have an '05 LJ Rubi with 74K on the engine. Original full rebuild at less than 1000 miles, currently on 3rd OPDG assembly.

Best of Luck


Mike - other than the original rebuild, on the subsequent to OPDG changes, did you also change the cam shaft? In other words, if the OPDGs were replaced due to wear, there would be corresponding wear on the cam gear as well. Just replacing the OPDG exposes the new gear to a worn cam gear, likely shortening the life of the new OPDG substantially.

I am not criticizing, just inquiring. I have 87k+ on my '-5 LJ and just pulled the CPS unit to check the wear on the gears. Both are showing wear, but have not progressed to the point of requiring replacement (yet). I expect that in the next 15-20k miles I will be replacing the OPDG and the cam shaft as well.

I will also be switching to a "high mileage" application oil from either Mobil or Castrol with the next oil change, but the horse is already out of the barn on this cam and OPDG.

As to the original post, I am comtemplating changing the cam to full roller, and/or changing the rocker arms to roller as well. There are higher spring pressures with the roller cam, but an entirely different dynamic at the intereface of the cam lobe and lifter.
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In my Rubi I just run 5W-30 Amsoil year round. No problems as of yet and I have 45k miles on her. Did the same with my other 4.0 and she ran like a champ and still does. I have 170k miles on that motor and it has never been rebuilt. I am in love with my first 4.0 and hope the same love affair can continue in this jeep
Now that some of the early "new" 4.0s (03-04) are starting to fail I am a bit concerned.

I rebuilt the motor at 12K miles due to a hydrolock (#1 and #2 rods were snapped in half by the original owner) and now have 105K on the Jeep, or 93K miles on the rebuild. At the time of the rebuild, the cam/lifters/crank/bearings were throughly inspected and deemed 'nearly new'. Just by chance I have always run Castrol Syntec 10w-30 which meets the ACEA A1/A5 specification. I feel that I should pull the cam position sensor to check the drive gear or excessive wear, if not just for my piece of mind.

I hope it does not have any cam or lifter issues in the next few years or I may be up a creek with out a paddle since my DD MJ is down to the shell!
desertfox1 said:
Here's another good read:


Thanks for the link, Doctor D is the best.

If you really think about it most 4.0 motors have ticking issues (after the "break-in period" oh and lets not forget how "bullet proof" our 4.0's are... told that by the Jeep Service Manager), I really do sum it up to poor oil flow.
My 04 ticks (sometimes) @ start up -if i shut if off re-start it its fine (don't know why)

have been running the ACEA-3 oil for years
Knock on wood, my 05 w/50k is running just fine with a replacement cam at about 3k (was recalled). Have run Mobil 1 HM 10W30 since new change every 4-5k or six months. It ticked once at startup while I was parked uphill, and had just put an amsoil filter in. That came out and it's never done it again.

Have not even checked my OPDG, it's not making noise and the jeep runs fine; rear seal has blown just enough oil to form a dry crud pile around but never dripped. Compared to the costs of wheelin damage I've done, motor seems just about perfect!
Mine had A1/A5 for the first 25K miles, and A3 for the last 45K. It ticks on startup once in a blue moon, never lasting more than 5 or 6 seconds. I'd say it has done it 4 or 5 times a year, since it was about 2 years old.
I was at Wal-mart the other day, looking at various bottles of oil. Two 5 gallon jugs of Mobile 1 10w/30 full synthetic had identical markings on the front of the bottle, but one had only API ratings on the back (the little circle that says SM, etc in it) yet the other bottle had the ACEA specs on it, which always seem to appear above the API rating.

in this thread: another member said they ALWAYS check the back of the bottle when buying the same oil they bought last time. The fact that I found two bottles of supposedly the same oil, points out that like said earlier, is that it is important to "look before you buy" when buying the same oil you always buy.
I always do the same. The Walmart store brand synthetic used to be A3, but now is just API rated. I used it as long as it carried the A3, but switched to Mobile 1 HM once they dropped the ACEA rating...
I have even seen Mobil 1 HM without the ACEA A3 designation. The big gallon jugs that you see on sale every now and then, notorious for NOT being ACEA A3.

Just as others, I read every bottle every time.
Okay. I think I'm doing the right thing.
I have always used the ACEA A3 M1 HM oil in a 10-30 flavor.
I use the big Donaldson filter usually, currently I have a Wix large size on.
I run Chevron with Techron gas or Shell gas to help keep the valve stems clean.
Although I feel silly pulling the OPDG deal out to check the gears at 19,000 miles I may do it.
I have an '06 model and warranty is good for almost 2 more years.

It looks like a high volume oil pump will help avoid issues. Is the addition of an after market oil pump going to void my warranty?
bob1340 said:
Is the addition of an after market oil pump going to void my warranty?

Not unless the unit fails and causes other damage (if you're looking at the Hesco unit it may be a good idea to ask Benny if he has ever seen a unit fail). Given you have an oil pressure meter you can monitor you should be able to tell if it's not working properly (*edit... I can't really say if the unit will void the warranty, that is a good question).
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