Why do new 4.0's die sooner?

I would like to know why the newer 4.0's seem to die sooner? Is it just assembly problems, or minor design changes? I am in deliberation on either building a stroker and keeping my jeep stocked with an I-6 or trying to find the time, and money to put a 5.9 in it. Without losing sight of the original question... I already have a discussion about the 5.9 going on elsewhere. What are the problems with the newer engines? Can these problems be remedied durring the build up of a stroker? If I build up a stroker, 4.6, I want it to last me well over 100K... hopefully even on par with the timelines of the 4.0 heritage... is this completely unrealistic?

I don't know what to tell you but my '98 has over 130K on it and runs like new. My wifes '01 had 78K on it when it decided to quit pumping oil. Actually her problem was either a bad head, head gasket, or block. There was lots of water going into the oil.

Either way the 4.0L dropped a notch on my belt when I had to replace her motor. Worst part is that the replacement motor got 3K on it when the oil pump drive froze up and damaged the cam drive among other things. The Jeep is now on it's third 4.0L.

B-loose

oye... i guess it's a good thing that my 00' is at 103K then, eh?

There's probably something to the new-vs-old bit...

I've got my 88, running 236K+, and doesn't lose any oil while running (but I've replaced most of the bolt-ons by now...)

My 87 lost its oil pump at about 200K. I replaced the pump, lifters, and crank, and put another 50K on it before it lost vacuum (should have replaced the rings along with everything else) and quit running. That was with a hole blown in the side of the block big enough to put your fist thru (I found the iron chunk and JB-Welded it back in place, it was on the sump skirt just above the oil rail, and was knocked out by the #6 rod...) It has since been promoted to "project truck."

And, my wife's 89 is the "new" one still under 200K (at just short of 190K - almost broken in) and the only major problem I had was a set of clogged lifters - the previous owner seemed to have had a habit of using Pennzoil (ugh!) Still going strong. Six quarts in, six quarts out (I measure the oil change once a year to keep tabs on things.)

5-90

I'd guess the 'bad' older engines have long since died, so you only have the 'good', long-life ones around anymore.

Just an oppinion, but improvements on a proven design have one chance in three of being actual imrovements. Either better, worse or pretty much the same.
Seen Chev. do the same thing with the redesign of the old 350 motor in the mid 80`s. Improved some things, that were actually an improvement, Improved or changed others that really messed with reliability.
Some of the design changes they made in hindsight, were really dumb.
Some/many of the old engineers in the 50`s were pretty darned sharp. Practical engineers, that made good reliable stuff. Didn´t learn there craft in the university, learned it in the garage.

oh well, i guess i'm just gonna have to trust the stroker to be done right then... which means that my dumb@$$ is nowhere in sight while it's being built (as much as I want to build it myself) Having never worked on internals of an engine before, i figured my stroker shouldn't be my first...

my opinion is that chryco and damchry didn't want the truck to last longer and so desinged flaws into it rhather than out of it. my buddies 89 is a way better truck than my 00 in every way except for interior...but i would give up interior comfort in exchange for reliability any day. he's in the 200,000 mi mark and it purrs like a kitten, mine however has more chatter (valve noise) and electrical probelms at 65k mi...so whats the deal?
i have heard here that the older engines had more nickel in the cast iron which makes it more durable.
as for engineers...the constraints put on them are pretty tight. gas mileage, features, and safety are what people are asking for and so the durability of the vehicles is taking back seat. look at the resale value of a 89-92 toyata pickup with huge miles and you will see what true durability and reliability will cost you...far better value than an XJ which cost the same new. perhaps this is apples and oranges...
so yeah do a search for nickel content and see if that sheds some light on things.

Maybe changes change things, maybe not. My 98 is headed for 250,000 or might even be just past there now. With the messed up sender I keep the trip odometer on and don't usually check the odometer. I have done my oil and filter changes, taken care of all the fluids, done my maintenance as needed and more. My 98 runs better than the first couple of weeks I had it for break in, still strong, still fires up, as reliable as a hammer, I would not hesitate to get in it right now and do a coast to coast and back as is. I attribute it to maintenance, though mobil-1 and good filters probably helped alot.
Could be that when the XJ was being discontinued the quality control went south from people fearing for their jobs and being a bit ticked off. I also consider the 97/98 to be the best years they made with the exceptions of the A/C evaporator and the fuel pump sender, never liked painted bumpers and wheel well flares, I'm too rough on all that painted stuff. Being in a hilly area I use 3rd gear alot around here from 30-60mph, with occasional forays into 4th being somewhat rare and 5th only on the once in a blue moon trips on big hiway to NJ or Phila...
As for '6 quarts in and 6 quarts out' , well, thats never happened to me, ever, I've never gotten more than 5 1/2 out even with draining the filter out on the catch basin at 3,000mi and at 5,000mi I get no more than 5 quarts back out...no idea where it goes, engine is clean with no oil leaks....

Audiophile...don't regard the 360 as a bombproof motor until you read some of the postings on the Dodge forums. I had one in my '01 Ram, and needless to say, in the couple of years that I owned it, it was anything but reliable.

nosajwp said:

Audiophile...don't regard the 360 as a bombproof motor until you read some of the postings on the Dodge forums. I had one in my '01 Ram, and needless to say, in the couple of years that I owned it, it was anything but reliable.

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As far as I am concerned, you get good ones and bad ones. The big thing about the 5.2/5.9 is the intake pan gasket. I had a 94 Dakota before the XJ and drove the crap out of it (reg cab, short bed with the 5.2/auto and 3.55 Trak-loc in the 8.25) and other than oil usage and maint (reg oil changes with mobil 1 and a good filter) that truck was unstoppable. :lecture:

I am with RichP on this one..... Qual control sucks when people fear the loss of jobs and I know that was the case in Toledo in 2k-2k1......

As for the stroker verses 5.9 in the XJ.... I love both motors but would have to say 4.6 all the way and stick with the AW-4 :wave:

All this FWIW
Travis

Yeah... i'm back to the I6 way of thinking... i was just thinking that if the swap was even only moderately hard, i could get the engine for a good price... so it might be fun... but i'm ghonna keep saving my pennies for the stroker and just got an e-mail backl from Avenger Superchargers and they told me what I wanted/expected to hear... the charger is easilly useable in a stroker situation, just add more gas. Ed from Avenger said that he is breaking in a 4.7L right now that he plans to supercharge once the break in period is over. Their supercharger adds 55% hp on a stock motor, i'm not sure how much it would lose off that # on a 4.7L but any way you look at it, that's going to be a monster of an engine!

Just my two cents, if your gonna supercharge, there are compression issues, most times they work better at lower compression. Got to be sure you have a substantial fuel supply (if you run it lean, the motor isn´t gonna last long) and cooling ( 30% more HP= more heat). Almost have to build the motor to supercharge. Or tone down the boost conciderably. Wouldn´t believe the size of radiator, I had to put in my Paxton supercharged 318.
The old low compression, carburated smog motors, worked well as a start for supercharging.
Maybe they`ve found a magic bullet, for supercharging motors with high compression. Doubt it. Most guys I know who´ve tried, there motors didn´t last long, mostly fried internals, occasionally catastrophy. They spent a lot of time and energy finding ways to slow down the burn and avoid detonation.

well, i guess i'l be waiting to see the verdict from Ed's testing... it'll be a while until i'm ready to supercharge... but I WAS planning on building it as supercharge-friendly as possible.

8Mud said:

Just my two cents, if your gonna supercharge, there are compression issues, most times they work better at lower compression. Got to be sure you have a substantial fuel supply (if you run it lean, the motor isn´t gonna last long) and cooling ( 30% more HP= more heat). Almost have to build the motor to supercharge. Or tone down the boost conciderably. Wouldn´t believe the size of radiator, I had to put in my Paxton supercharged 318.
The old low compression, carburated smog motors, worked well as a start for supercharging.
Maybe they`ve found a magic bullet, for supercharging motors with high compression. Doubt it. Most guys I know who´ve tried, there motors didn´t last long, mostly fried internals, occasionally catastrophy. They spent a lot of time and energy finding ways to slow down the burn and avoid detonation.

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If you supercharge a high compression motor you need to put the corresponding octane rated fuel in it too. I remember a long time ago seeing a table somewhere that listed compression ratio vs octane requirements. The one that sticks in my mind was 12.5:1 needing 130 octane, sunoco 280 back then, aircraft fuel. My 67 427 mustang would get downright nasty with anything below sunoco 240 and was happiest with sunoco 260 which was an outrageous .35 a gallon in 69.... The L88 vettes and 426Hemis had similar requirements...

Well from what I've been able to gather, the older Renix 4.0's last longer because they have a higher nickel content in the metal making the engine more resistant to warping and wear. The newer HO engines by Chrysler have a lower nickel content making them slightly more prone to damage due to heat and excessive wear. It really seems to be a luck of the draw though on the newer engines I've heard stories of them needing overhaul at 80k, and I've heard a couple of stories where they're 200k and going strong.

My renix 4.0 is coming up on 200k and was maintained poorly and still running strong

I did a long boring 10 page paper on why cars are getting crappier. THe finance department of automobile companies has the engineering department by the balls, and there not afraid to twist. No more inginuity, just cheaper stuff. Which in the long run hurts everone, the economy but imediatly the product. The Reckoning by David Halberstam is a good book if you are interested in all this jazz. The older is better because it wasnt made cheaply.
-Steve D

Got an electronic copy? I'd be interested in your analysis...

5-90
[email protected]

I read on a prior thread here that in 2000 they changed the casting of the head. This casting has resulted in a weaker area between the 3 and 4 cylinders if I remember correctly. This thread was on here about 1 or 2 weeks ago. I'm not sure why the hell anyone would mess with a good thing.

My 4.0L is a 99 with 114,000miles on it with no problems. I've been doing regular oil changes every 3-5K miles with filter. I'm hoping to get over 200,000 miles on it. Might just change to synthetic and extend the change interval.

MAP

Here's the post.

Dr. Dyno said:

Has the engine overheated recently? The 0331 heads on the newer 4.0's have been known to crack on the top side between the no.3 and 4 exhaust ports and if that's what's happened in your case, it's bad news. You might not get any coolant contaminating the oil but merely be losing coolant through the exhaust. I suggest you get the cooling system pressure tested to see if you do have an internal leak. Take the radiator cap off and run the engine at idle. Bubbles constantly appearing in the radiator are probably from the exhaust and will be a sure sign of either a cracked head or a head gasket leak.
The oil pressure is a definite concern. Assuming that the oil level in the pan is correct, you have a new oil filter (not Fram I hope), and the 10psi oil pressure reading at idle is correct, you'll probably need to remove the oil pan and investigate. Possibilities include worn oil pump (unusual at only 62.5k miles), clogged oil pump pick up screen, or worn rod/main bearings.
These are not the sort of problems you'd expect to find on such a low mileage engine but if you only bought your Jeep fairly recently, can you rule out the possibility that it was abused by the previous owner?

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