Hey everyone. I recently bought an 01 Cherokee with the dreaded 0331 head. I'm sure this question has been asked many times, but I can't find good answers. What can I do as the owner and maintained of the jeep to lower my chances of the head cracking, maintenance wise?

Thanks
USAFlyer3000

 

My first question is what does the oil look like?
Next I would look down the oil filler cap looking for the letters TUPY.
If you see them that means the head has been swapped out and this is a good thing.
Not cooking the engine would be a good start. Not that guys have reported cracked heads in an engine that was never cooked but...
So I would flush the system and put in fresh anti-freeze. Make sure that the cooling system is operating as it should.
That includes making sure your fan clutch operates as it should and that you have the shroud around your mechanical fan.
Thinking I would change the oil.
Then you drive it. Keeping an eye on your temps and for the common symptoms associated with a cracked 0331 head.
Milkshake looking oil, unexplained loss of anti-freeze, and little or no oil pressure at a very hot idle.
And so you know 13 lbs at a very hot idle is acceptable.
Probably should hook up an oil pressure tester to get an accurate reading.
I rigged up my '00 so that I could run the cluster gauge and the tester at the same time to see how the two compared to each other.
Let her idle in my driveway for a long time to get her nice and hot. About 22 lbs at a very hot idle and the cluster read about the same.



And none of this means the head will never crack. Just if it happens you want to catch it quick before it trashes the lower end.
My '00 was a kinda running not really drive-able purchase 7 years ago. Was aware of the head issue going in.
Well best I can tell all is fine. I just don't know if it is the original head or been replaced by one of the previous owners.
I do know it is not a TUPY head though. Very OCD about maintenance. I use green anti-freeze and swap it every other year.
I pull plugs yearly, especially to look and #3 an #4, see if anything jumps out at me.
Have run a compression test and a block test also. And at some point want to do a leak down test.
Not for any problems just trying to get a handle on what the condition of my engine might be.

 

Also look for the "0331: molded into the top edge of the head right next to the valve cover on the throttle body side. It'll be under any heat shield that may be there. If it's not there, it's a Clearwater or other aftermarket head. There once was an "Alabama" head available. SO...no markings, it's not an 0331. With markings and no "TUPY" inside the valve cover, it's an original head that has to be watched. Take a close look at this picture:

 

The BEST answer I ever heard was:

"There are 2 types of 0331 heads. Those that have cracked, and those that are going to crack."

 

Admittedly, it's like shooting dice. Sometimes you get lucky, sometimes not. I'm beginning to think the problem is those cast iron exhaust manifolds causing a hot spot in the worst possible place any straight cylinder engine could have. Right in the middle. Ask yourself, where do blown head gaskets usually happen? Answer, in the middle of a bank of cylinders where thermal flexing is at it's worst.

 



 

About the only thing I can think of that might help is to get a steel tube header and adapter for it. Then move the converters farther down the exhaust stream. This would require fabricating a custom split header and exhaust pipe and extending the 02 sensor leads. This might not even work. I'd be curious to know the figures on how many Federal emissions jeeps heads cracked as opposed to how many CA emissions jeeps heads cracked.

 

^^ that would be a good stat to know. Mine is a CA emission jeep although I don't have proof but I do believe my head has been replace as not a 0331 number showing thru filler hole or on pad outside of valve cover and exhaust gasket looks new and appears to be two of them stacked together.. I have too many tell tell signs like low oil pressure for a jeep with less than 140k besides head and gaskets looks new. Right now mine idles hot at 8-11psi and at 1800-2000 rpm its like 35-38 psi not really low on off idle low but feel it should be higher and this is with 10w40 oil and a MC oil filter. No bad knocking so gonna run it till it blows!

 

Damn 18 Jeeps?!