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Old 06-08-2012, 10:57 AM   #1
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4.0 Cracked Head

Just been reading about the common problem of a cracked head on early TJ's with the 4.0.

I'm worried that I may have one of the weak heads in my Jeep. I noticed the coolant has been low and have replaced some twice now in about a month long period.

Apparently, the problem head is stamped 0331 and was used from late '99 till around '01. Just checked the build date on my TJ and it's 4/00

I'm at work now so I can't look to see if I have that head but with my luck I'm almost 100% sure that's what the problem is.

Only had my Jeep for a month and now I'm wishing I would have done more research before buying her

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Old 06-08-2012, 11:53 AM   #2
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sucks to have that problem, used heads with low nickel content and thats what resulted. a lot were replaced and have a TPU on the them and those heads are not the problem ones. if you have an original 0331 good chance its cracked, only way to tell is the pull it and have it checked to be sure other than guessing unless its cracked badly and u can see the mixing of antifreeze and oil forming a line in the crack between #3 and 4 cylinders

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Old 06-08-2012, 02:13 PM   #3
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I haven't went out to look at the number on the head to see if its a 0331 but I'm certain it is. Not sure what to do now, keep it until the inevitable repair or sell it or trade it in and take a hit on the value.
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Old 06-08-2012, 02:25 PM   #4
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A leaking radiator or a water pump going out are a lot more common causes of coolant loss. I wouldn't panic yet!
If it is the head, bite the bullet and get it fixed and never have to worry about it again.
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Old 06-08-2012, 05:18 PM   #5
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Just went out to see if I could find the cast number on my Jeeps head. I had some trouble finding it but then unfortunately, I finally saw the ugly number 3.

I've decided to just hang on to it for now and maybe get the head replaced on down the line.

Does anyone know if it would be possible (or cheaper) to have a machinist weld the crack as opposed to buying a new head?
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Old 06-08-2012, 05:20 PM   #6
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A leaking radiator or a water pump going out are a lot more common causes of coolant loss. I wouldn't panic yet!
If it is the head, bite the bullet and get it fixed and never have to worry about it again.
I hope you're right about the pump or radiator but so far I haven't been able to find a leak anywhere
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Old 06-08-2012, 09:25 PM   #7
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Ive seen a few cracked heads & on the ones I saw I could look in the oil fill hole & see the crack.
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Old 06-08-2012, 10:05 PM   #8
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Ive seen a few cracked heads & on the ones I saw I could look in the oil fill hole & see the crack.
I've read that others have been able to do this as well. I'm going to give it a try tomorrow and see if there is a crack.
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Old 06-08-2012, 10:28 PM   #9
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check your oil if its kinda milky there is water in it if not there is something ells might be a head gasket. pressure up your cooling system and see if you see leaks if not pop the oil cap off and see if you see any coolant if you still see nothing might be the gasket. i am in the same boat i have an 01 with 120000 mi and i am seeing what happens. i work on motors a lot so any other questions let me know.
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Old 06-09-2012, 01:51 AM   #10
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I wouldn't drive it too long, or it could hurt the rest of the motor.
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Old 06-09-2012, 02:17 AM   #11
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check your oil if its kinda milky there is water in it if not there is something ells might be a head gasket. pressure up your cooling system and see if you see leaks if not pop the oil cap off and see if you see any coolant if you still see nothing might be the gasket. i am in the same boat i have an 01 with 120000 mi and i am seeing what happens. i work on motors a lot so any other questions let me know.
Checked the oil on the dipstick today and no signs of milky oil on it. I changed the oil last week and everything seemed normal.

I've heard about people pressurizing the coolant system but I've never figured out they do it. Do you connect an air compressor somehow?

I appreciate the advice!
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Old 06-09-2012, 02:27 AM   #12
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The crack in the head assuming there is one, may not necessarily lead into an oil passage, and may go directly into the combustion chamber, and depending on how big the crack is it may not be letting enough in to see smoke out of the tail pipe, but you might be able to smell it
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Old 06-09-2012, 03:11 AM   #13
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Originally Posted by iflylow74 View Post
Checked the oil on the dipstick today and no signs of milky oil on it. I changed the oil last week and everything seemed normal.

I've heard about people pressurizing the coolant system but I've never figured out they do it. Do you connect an air compressor somehow?

I appreciate the advice!
Any mechanic should have specialized tool that they can use to pressurize the radiator. Have them remove the valve cover before they do it and look closely between the #3 and #4 cylinders. If you have a cracked head, you might be able to see coolant leaking through the crack. It may look something like this:


If you have a leak, don't wait to repair or replace the head. If you do, the coolant will destroy certain parts in your motor, such as the rod bearings and lifters. If that happens, you may notice lower oil pressure than usual and noisy lifters. At that point, you either need a complete rebuild or a new motor.

If you can't afford to repair it now, stop driving your jeep until you can get it fixed.
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Old 06-09-2012, 11:03 AM   #14
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The crack in the head assuming there is one, may not necessarily lead into an oil passage, and may go directly into the combustion chamber, and depending on how big the crack is it may not be letting enough in to see smoke out of the tail pipe, but you might be able to smell it
I haven't noticed any smoke or smell from the exhaust but once I did notice a slight smell of coolant when I was pulling out of the driveway with my window down. Reminded me of when my heater core went out in my Chevy.
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Old 06-09-2012, 11:12 AM   #15
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Checked the oil on the dipstick today and no signs of milky oil on it. I changed the oil last week and everything seemed normal.

I've heard about people pressurizing the coolant system but I've never figured out they do it. Do you connect an air compressor somehow?

I appreciate the advice!
I have a pressure kit.It is a adaptor that screws onto the rad neck like the rad cap then you use a pump thats connected to that adapter with a hose and just pump it up until you get the desired amount of press in the sys.Safety glasses needed also!
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Old 06-09-2012, 11:43 AM   #16
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I have a pressure kit.It is a adaptor that screws onto the rad neck like the rad cap then you use a pump thats connected to that adapter with a hose and just pump it up until you get the desired amount of press in the sys.Safety glasses needed also!
That's cool, I learned something everyday!

Unfortunately it won't be necessary now. I just took a look under my oil fill cap and there was the neon green of coolant under the cap. My heart sunk to the floor.

Man I wish I would have done more research before buying!!!

My love affair with my Jeep is officially over, time to start figuring out what plan B is
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Old 06-09-2012, 09:00 PM   #17
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That's cool, I learned something everyday!

Unfortunately it won't be necessary now. I just took a look under my oil fill cap and there was the neon green of coolant under the cap. My heart sunk to the floor.

Man I wish I would have done more research before buying!!!

My love affair with my Jeep is officially over, time to start figuring out what plan B is
its cheaper to repair then to just replace you jeep. its only your head not the hole engine get a quot from a few local mechanics it shouldn't be overly expensive. if you were closer i would do it for you. sorry to hear the bad new. get some quotes and go from there it should be under $2000 its not that hard or expensive for the parts. good luck
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Old 06-09-2012, 09:51 PM   #18
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its cheaper to repair then to just replace you jeep. its only your head not the hole engine get a quot from a few local mechanics it shouldn't be overly expensive. if you were closer i would do it for you. sorry to hear the bad new. get some quotes and go from there it should be under $2000 its not that hard or expensive for the parts. good luck
After talking with my wife we've decided the same as you that we'd be better off fixing instead of selling.

I appreciate you kind offer to help me with it! I wish you were closer too!

I think next week I will get some quotes on the new head install and go ahead and get it done so it will be ready before deer season.

Worse case scenario, I have a friend whose a mechanic who might be willing to help me work on it if the professionals are too expensive.
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Old 06-10-2012, 08:39 PM   #19
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Its really not a hard job.Just time consuming.
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Old 06-10-2012, 09:37 PM   #20
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Its really not a hard job.Just time consuming.
I may end up doing it myself if the mechanics ask too much to do it . Do you know if there are any special tools needed?

I'm not the best mechanic but I put a new crank and all new bearings in my Willys once so I think I could handle it if there aren't any special tools involved.
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Old 06-11-2012, 05:47 AM   #21
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I may end up doing it myself if the mechanics ask too much to do it . Do you know if there are any special tools needed?

I'm not the best mechanic but I put a new crank and all new bearings in my Willys once so I think I could handle it if there aren't any special tools involved.
No special tools needed.What I do is I get new head bolts then I take 2 of the old bolts,cut the heads off & put a slit on the end so i can use a reg screw driver on it.I now have a couple "guides or studs" to slide the head onto the block.The head is very heavy & this makes it a lot easier.
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Old 06-11-2012, 11:22 AM   #22
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I spoke with a mechanic today and he said he could do the job for around $800 parts included.

I also asked him if the new head would be stronger and less likely to crack. He said he couldn't say for sure if the new heads are better but that the 4.0 motor was "expected" to have one cylinder head change in it's lifetime. (not sure if he used these exact words but something close)

Has anyone else heard this? I would hate to spend that kind of money just to have another cracked head in 50,000 miles.
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Old 06-11-2012, 11:50 AM   #23
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Is it a NEW head or just a new, good, reworked head?
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Old 06-11-2012, 11:56 AM   #24
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Is it a NEW head or just a new, good, reworked head?
Good question, I was assuming a new head but not for sure. If I decide to go with him I'll ask to find out for sure. I bet at that price it's a re manufactured one.

On a side not, I called the local Jeep dealer for an estimate and they quoted me $2200!!! I can get a crate motor for that price!
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Old 06-11-2012, 01:30 PM   #25
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I sell new castings and use your valves, springs for 450.
Just to give you an idea.
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Old 06-11-2012, 01:39 PM   #26
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I sell new castings and use your valves, springs for 450.
Just to give you an idea.
Thanks for the info, sounds like a fair price. The problem is, this mechanic told me he won't install a head that I bring because he will only stand behind the one he orders.

Makes me think that surely the one he orders will be a decent one. If I can get another 100,000 miles out of it then I'd be happy.
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Old 06-11-2012, 08:22 PM   #27
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That sounds like a fair price if he is a good mechanic.I still think you should do it yourself if you have the mech ability & a place to do it.
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Old 06-11-2012, 09:01 PM   #28
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Get a quote from Alabama cylinder head and find a knowlegable mechanic to install it and be done! Or install it yourself!
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Old 06-11-2012, 09:29 PM   #29
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I've heard a lot about Alabama cylinder head and also Clearwater Cylinder heads. Seems like clearwater is a little cheaper but not sure if there's a quality difference. I'd really like to do it myself but just a little chicken I guess since its my DD
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Old 06-11-2012, 09:38 PM   #30
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fly how meany miles are on your jeep? i have a week off at the end of July and i have the worry about mine. i normally do a road trip with my friends on my week off. i don't want it to crack away from home. just getting an idea of how long or over due i am for my head.

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