Jeeps are cracking heads

[HawkeyeScott]

I was just reading in the Gas UOA forum about some late model Jeep 4.0s having a tendency to crack heads. I hadn't heard this before, so my ears perked up when I read it. I'm particularly curious since my wife has a 2001 Cherokee, which we bought with plans of driving very long term.

So what do you know about this? Is it luck of the draw? Is it happening in cold weather areas? Anything a guy can do to prevent it? Like I said, this is the first I've heard of it, so is it even that big of a deal?

Thanks for any thoughts.

 

[VNTS]

Havent heard of that, go over to the jeeps unlmited board and ask on the WJ section.

it cant be to much of an issue or they would be $itching over there.

 

[D189379]

I know it's the 0331 head used in 2000 and 2001 Cherokees. I'll post some links when I get home.

 

[HawkeyeScott]

Thanks, I'll be anxious to see those.

I assume that head was used in all 4.0s in those models?

 

[D189379]

Quote:

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Thanks, I'll be anxious to see those.

I assume that head was used in all 4.0s in those models?

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I know it started in the 2000 models and maybe up until 2003?

Here's a link. (Hope I'm not breaking any rules?)
http://jeepsunlimited.com/forums/showthread.php?t=721472&highlight=cracked+head

You could also go to www.naxja.org or www.jeepforum.com and search for cylinder,head, crack, etc.

Try not to get too freaked out about it. There are alot of people that haven't had issues and have put alot of miles on their 4.0's.

 

[Chris142]

The heads are cracking under the valve covers....Not in the combustion chamber side like heads normally do.

 

[Gary Allan]

4.0 heads are cheap and relatively easy to change.

 

[sw99]

Is there any other way of checking to see if I have one of the bad ones? The dealer installed that heatshield contraption on my 4.0L and I cannot see where the nubmer is cast into the drivers side. My WJ is a 2000 also. I think a UOA is in my near future.

 

[Greaser]

If you are loosing coolant and there is a milky mash under your oil cap in the valve cover look-out.I've talked to my brother ,whom is a 30 year D/C tech at a major dealership in this area, and he said he hasn't seen/heard of a great rash of cracked Jeep heads.

 

[Challenger71]

My 01 XJ is solid as a rock. The issue has circulated for some years now but it is very rare to hear about it let alone actually experience it. You can go get a compression test if you're really concerned about it but I would'nt remotely lose sleep over it, I'm not.

 

[D189379]

Quote:

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If you are loosing coolant and there is a milky mash under your oil cap in the valve cover look-out.I've talked to my brother ,whom is a 30 year D/C tech at a major dealership in this area, and he said he hasn't seen/heard of a great rash of cracked Jeep heads.

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I don't doubt he hasn't seen a lot of these. These usually happen around the 80 to 90 mile mark. So most likely they are out of warranty, and the difference in price between the dealer in my area and an independent shop is about $900 to $1000.

I don't think this affects a lot of Jeeps. Apparently there's just a bad batch of heads out there. Like everyone is saying, it's not a huge problem and it doesn't effect a lot of 4.0's. A few months ago I was one of the people saying how exaggerated the problem was. Just keep an eye on your coolant.

Correct me if I'm wrong, but I think since 2000 all 4.0's had the 0331 head. I guess time will tell if this was a one time problem or an ongoing one.

 

[g20ooh]

1 ) On some of this casting # 0331 it appears as of 1MARCH07 ( way to few to tell ) - If the cooling system is neglected , abused or really " overloaded " ( almost to the point of severe - need to rebuild damage in general ) then you can get this weird little crack from the outside in .


2 ) Also , this has shown up on some rebuilt heads that " PROBABLY " were overstressed as per the above .
This may have to do partially or fully with rebuilding procedures depending on the head .
( My opinion only ; think rapid severe heat and then cycled .)




Easy fix either way - you don't have to get another core - unless its attractively cheaper .
If this occurs it would be wise to correctly and fully service the cooling system at the very least .


Can't give you the first , but here is the second .



The following is an acceptable excerpt ( strictly defined ) from essentially an synopsis .

The full description is obviously at AERA .


Cylinder HeadCracks On 1999-2004 Chrysler/Jeep
4.0L VIN S Engines

The AERA Technical Committee
offers the following information regarding cylinder head cracks on 1999-2004 Chrysler or Jeep 4.0L VIN S engines.



Reports have been received concerning coolant loss on engines shortly after a valve job .


After no visible signs of external coolant leakage were found, the cylinder head was removed for
inspection.


After chemical cleaning, a magnetic particle inspection process was implemented on the suspect cylinder head.
No positive indications were found.


Additional testing was done by performing a submerged pressure test.
The test revealed a slight leak between the rocker arm stands on the topside of the head.
This head carries the casting number 0331.


After the head was removed and dried, the casting was again
checked by magnetic inspection in the leaking area.


No “real”cracks were found, only what was described as “false” impressions or a “rotten” looking casting.

The area was repaired by spray welding and returned to service.

Perhaps this thread belongs in our service / maintenance and repair section ?

 

[widman]

One of the tricks to that engine (I had a GCL for several years) is purging the air from the cooling system when changing coolant. It traps air and has to go through 2 cycles of heat/cool to draw from the overflow tank. Otherwise you risk overheating (and not admitting it or relating this error to the problem)

 

[Chris142]

Quote:

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One of the tricks to that engine (I had a GCL for several years) is purging the air from the cooling system when changing coolant. It traps air and has to go through 2 cycles of heat/cool to draw from the overflow tank. Otherwise you risk overheating (and not admitting it or relating this error to the problem)

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That may work but the proper way is to fill the cooling system through the heater hose that connects to the stat housing.

Put a funnel in the removed hose and fill it through the heater core. When water starts to come out the place on the stat housing where the heater hose goes put the heater hose back on and fill the radiator the rest of the way.