2001 Jeep WJ with 4.0 engine

[jeepman3071]

Originally Posted By: MrRPM
right, i know what the problem is, i have a 2001 so i keep my eyes peeled and am always checking over things to make sure it hasn't happened. Next to that i hear about piston skirt failure (but have only seen 1 real case here it appears, haven't seen it anywhere else, just "heard" about it.) I have also seen tons of oil pump drive gears stripping out on 05/06 wranglers on the web. People are always talking about common problems that can cause failure of the engines. That to me says they aren't the reliable tractor engines they are made out to be. Im also thinking maybe i just spend alot of time online where people go to discuss the problems and I see it alot and feel like its over discussed lol



Like you said I think it has a lot to do with discussion forums. Often people will have a problem and seek out an online forum for help. According to jeepforum.com, about 1/3 of the 0331 heads crack, but that only includes the members of the site, and those who actually cared enough about the issue to participate in the poll. There are many more out there running flawlessly that go unnoticed.

Mine overheated so I replaced the head as a preventative measure even though it never cracked. My previous 2000 XJ didn't crack for the year I had it, my friend's 2000 XJ hasn't cracked yet, and my other friend's 2001 XJ hasn't cracked yet also. I'd just keep up with the maintenance and you will be golden. I've seen later 4.0s that were hydrolocked, then restarted, and some that were even run upside down.

 

[MrRPM]

Originally Posted By: jeepman3071


The 4.0L has had the same basic design its whole life. A few things were changed here and there mostly for emissions reasons. In 1999, they switched to a different head casting (0331) which had smaller exhaust ports to heat up the cat converters faster.


so when replacing the head am i getting an older style head with larger exhaust ports or am i getting the same exhaust ports just a stronger cast that wont crack?

I sure would like to open up the jeep with larger ports if i ever do need to replace the head, i dont care about the Catalytic converters at all. In my area they do no testing, id love to just rip em out but the down stream O2s would get angry. so id like to run high flow cats that keep the jeep running right but after that i dont care since i dont get tested.

 

[Kuato]

Just avoid the 0331 head. Not only did it have smaller ports, but the casting was of an inferior metal, and developed micro cracks after 90k miles or so. Anything before late 98 or after 2001/2 should do ok for you. I had a 1999 GC, and it smelled of coolant from about 80k up until I traded it at 140.

To OP: Yes the 4.0 has flat tappets. I'm currently doing an oil test on the Grand Cherokee with that engine, and M1 (low ZDDP) created more than twice the iron (49ppm) than did Valvoline conventional or Amsoil (21 and 19, respectively).

 

[KCJeep]

Originally Posted By: Kuato
Just avoid the 0331 head. Not only did it have smaller ports, but the casting was of an inferior metal, and developed micro cracks after 90k miles or so. Anything before late 98 or after 2001/2 should do ok for you. I had a 1999 GC, and it smelled of coolant from about 80k up until I traded it at 140.

To OP: Yes the 4.0 has flat tappets. I'm currently doing an oil test on the Grand Cherokee with that engine, and M1 (low ZDDP) created more than twice the iron (49ppm) than did Valvoline conventional or Amsoil (21 and 19, respectively).


That's interesting...Mobil 1 has been getting rapped a lot though for high iron UOA's so it would be hard to know for sure if it was the ZDDP or just the Mobil 1 syndrome. Good old Valvoline came through, it is consistent.

I'll be doing some UOA's on my 4.0 as well, as far as I can tell they tend to shed some iron, anything around 20 is about as good as its going to get, you think? Or can I hope for even less???

 

[edvanp]

I have a 99 Cherokee Classic with 186k miles on it (bought it 12k miles ago for my daughter). I have no idea what the history of it is, I got it from a friend who works at a dealership. Anyways, the engine was a bit noisy, especially on startup. I added a pint of Liqui Moly MoS2 Antifriction Engine Treatment that I picked up from my local NAPA store and it quieted right down.

 

[KCJeep]

I also noted there are some UOA's for 3.6L GM DI engines posted that are also well known for high iron UOA's. One fellow is getting about half the iron of the others that are using high dollar syn's, he's using plain old Valvoline conventional. Interesting. I'm gonna have to put some VWB on my "to try" list.

 

[Greaser]

1999 Cherokee 376,000km and a 01 TJ 275,000km both bought new always used HDEO no engine issues and still running strong !

 

[jeepman3071]

Originally Posted By: MrRPM
Originally Posted By: jeepman3071


The 4.0L has had the same basic design its whole life. A few things were changed here and there mostly for emissions reasons. In 1999, they switched to a different head casting (0331) which had smaller exhaust ports to heat up the cat converters faster.


so when replacing the head am i getting an older style head with larger exhaust ports or am i getting the same exhaust ports just a stronger cast that wont crack?

I sure would like to open up the jeep with larger ports if i ever do need to replace the head, i dont care about the Catalytic converters at all. In my area they do no testing, id love to just rip em out but the down stream O2s would get angry. so id like to run high flow cats that keep the jeep running right but after that i dont care since i dont get tested.



This all depends on your manifold. Does your TJ have the 2 mini-cats on the manifold? If so then you have 4 O2 sensors (California emissions package) and will need to get the later style 0331 head to match your manifold. If you remove those O2 sensors then your jeep won't run right. They make 0331 heads, just improved versions.

Alabama Cylinder head and Clearwater Cylinder head are two companies who make beefed up versions of the 0331. Jeep 4.0's from '03-'06 have the revised casting that won't crack. They will have "TUPY" cast into the head.

If you have the Federal emissions manifold with only one cat converter, then you can swap in the older style exhaust manifold and older style head for more flow.

 

[MrRPM]

I have 2 pre-cats =(

One of these days Im going to pop the valve cover just to end this, if its the flawed head ill replace it and if its already been replaced (i have only owned it for 1 year) with a TUPY head then ill be very happy and sleep better at night.

 

[jeepman3071]

Originally Posted By: MrRPM
I have 2 pre-cats =(

One of these days Im going to pop the valve cover just to end this, if its the flawed head ill replace it and if its already been replaced (i have only owned it for 1 year) with a TUPY head then ill be very happy and sleep better at night.


I use my jeep to commute to college everyday and it is my only vehicle. The 0331 never cracked but as a preventative measure I put on an Alabama head while I had the money, time, and help available a few summers ago. Its not a bad job if you have a good service manual and a buddy to help you. I did it slowly over a weekend. My jeep has been dead reliable so far.

If you don't want to shell out the money for an Alabama or Clearwater head, you can find a TUPY head at the junkyard and swap it in. They are found in 2003-2004 Grand Cherokees and 2003-2006 Wranglers with the 4.0L.

 

[Chris142]

Originally Posted By: jeepman3071
Originally Posted By: Chris142
Pretty common problem with the 2000 and up engines.


I doubt it is common with 2000 and up engines. What is your statement based on? More of them have issues with the 0331 head cracking than piston issues.
The heads crack too. I get my info from the many threads about the problem on Jeepforun and Jeeps unlimited.

 

[Chris142]

Originally Posted By: jeepman3071


If you don't want to shell out the money for an Alabama or Clearwater head, you can find a TUPY head at the junkyard and swap it in. They are found in 2003-2004 Grand Cherokees and 2003-2006 Wranglers with the 4.0L.
My 02 TJ built June 02 has the TUPY head

 

[jeepman3071]

Originally Posted By: Chris142
Originally Posted By: jeepman3071


If you don't want to shell out the money for an Alabama or Clearwater head, you can find a TUPY head at the junkyard and swap it in. They are found in 2003-2004 Grand Cherokees and 2003-2006 Wranglers with the 4.0L.
My 02 TJ built June 02 has the TUPY head

Yeah 2002 was the in between year. Some have the TUPY head some don't depending on the build date. I told him '03-'06 because I didn't want him to have to pull any more valve covers at the junkyard than he has to.

 

[84zmyfavorite]

The valve spring tension is a bit Higher on 87 thru 95 Four Point Ohz, when they went with the beehive shaped valve spring in 96 on the first year NVH 4.0(Noise,Vibration,Harshness), the spring tension lowered a bit to around 100 ftlbs. Low spring pressure lets the feet of the flat tappet and cam lobes alive for sometimes around 300,000 trouble free miles with some Four Point Ohz on just plain Ol 10w-30 Whatever. I have six Cherokees in my possesion now, 4 of which have the Inline 6, from a first year 1987(with currently 293,948 miles on her original everything, a 96 with a bit under 249,000., a 99 with her freshly Built 4.0 this past fall, all broken in now, and my Beloved 2001 SilverStones 64,620 mile 4.0 that All dont mind to much What motor oil they get. Im startin to believe these Jeeps dont Like tooo much Special treatment or Exotic Fluids or components. They just like Good, Basic, regular maintenance,..and to be Driven.

 

[84zmyfavorite]

I have given my 2001 XJs 4.0 some High Quality oil changes over the years, from Mobil 1 Extended Performance 10w-30 with Wix or NAPA Gold oversized 15151 oil filters, to her first oil change I performed on her with Royal Purple 10w-30 and a 301(oversized) K&N oil filter back in September 2006 when i First got Her with 49,420 miles to SuperTech 10w-30 and a Fram PH8(oversized), and I dont think she even Knew the difference. Current Fill for my 2001 SilverStone Merallic Cherokees 4.0 is Quaker State 10w-40 with a Fram PH8. PlainJane and I Think She Loves It.

 

[84zmyfavorite]

My other three Four Point Ohz get run Hard on whatevers on sale at OReilleys or AutoZone. I do Believe a Low mile, GudNTight clearance 4.0 prefers a thinner motor oil, 5w-30 in Cold temps, 10w-30 for just about anywhere, any temp. Shell Rotella T5 10w-30, Castrol GTX High Mileage 10w-30, and Valvoline MaxLife 10w-30 are what I would recommend for Your WJs 4.0!

 

[84zmyfavorite]

Six quarts of one of those brands, not all three mixed together...

 

[KCJeep]

Originally Posted By: 84zmyfavorite
I have given my 2001 XJs 4.0 some High Quality oil changes over the years, from Mobil 1 Extended Performance 10w-30 with Wix or NAPA Gold oversized 15151 oil filters, to her first oil change I performed on her with Royal Purple 10w-30 and a 301(oversized) K&N oil filter back in September 2006 when i First got Her with 49,420 miles to SuperTech 10w-30 and a Fram PH8(oversized), and I dont think she even Knew the difference. Current Fill for my 2001 SilverStone Merallic Cherokees 4.0 is Quaker State 10w-40 with a Fram PH8. PlainJane and I Think She Loves It.


Spot on. My 2004 WJ clearly prefers the to be on the thinner side of grade, whereas my 99 XJ would take about anything without so much as a hiccup.

 

[84zmyfavorite]

ALWAYS Thinkin of what Oil Best Fits my Four Point Ohz...