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Unread 12-12-2012, 01:54 PM   #1
dropkicksam
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Cracked head?

New XJ owner here - I just bought a 2000 with 103,000 miles a few weeks ago and have since put about 600 miles on it (right at 103,600 now). Everything is running great. When I bought it, the heat was only working intermittently, but the guy said he had the thermostat and everything checked out and it was fine. About two weeks in, I found the coolant reserve empty, so filled it up, and heat worked. 50-60 miles later, I checked the coolant - all gone. Filled it up again, let it sit idling in the driveway for an hour and it leaked no coolant. Drove about 50 more miles, and it was empty again. Coolant under the radiator cap looks clean. Some white smoke coming out of the exhaust when cold, but it slowly goes away and there is none when running hot. No overheating issues - sitting just below the 210 mark since I've owned it. Oil pressure sits at 45 upon starting, about 20 at idle after warming up. Oil on the dipstick looks perfect, but under the cap looks like chocolate milk. I tried to look for a crack in the head under the oil cap but, as you know, it's hard to see in there. What do you guys think? I can post some pictures later if it'll help.

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Unread 12-12-2012, 02:23 PM   #2
BigByrd47119
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Chocolate milk oil and disapearing coolant sure sounds like it.
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Unread 12-12-2012, 02:26 PM   #3
austin6137
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Yup I get you got cracked head
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Unread 12-12-2012, 02:41 PM   #4
buildin1XJ
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Cracked head. Google 0331 heads which is what you have on a 2000 and 01 models and are known for cracking between #3 and #4 cylinders.Please stop driving it ASAP before it destroys the bottom end and have to replace the entire engine.You can buy a new beefed up head from Clearwater cylinder heads which have a very good reputation.
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Unread 12-12-2012, 03:39 PM   #5
dropkicksam
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OK, just looked in again and saw some coolant under the oil cap. I have some questions that I haven't seen answered elsewhere that I'm just curious about. Don't really know much about Jeeps (or cars in general) and trying to learn a little here:
1. Why is it so certainly a cracked head and not necessarily blown head gasket? Seems the symptoms would be similar.
2. Why no overheating?
3. Why no chocolate milk on the dipstick?
4. About how much should installation of the new head cost?
5. What else should be done while the head is off? New head gasket, thermostat...anything else?
6. I'm going to have to drive it out of the city 30-40 miles to get it worked on. Anything I should do beforehand to prevent further damage?
7. How do the Jeeps generally fare after replacing the head? I have no idea how long it's been driven like this since I just bought it, so the vehicle history is not really clear to me. Hoping it can still last a while though, especially with this immediate investment I'm going to have to put in.
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Unread 12-12-2012, 04:06 PM   #6
dmill89
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Quote:
Originally Posted by dropkicksam View Post
OK, just looked in again and saw some coolant under the oil cap. I have some questions that I haven't seen answered elsewhere that I'm just curious about. Don't really know much about Jeeps (or cars in general) and trying to learn a little here:
1. Why is it so certainly a cracked head and not necessarily blown head gasket? Seems the symptoms would be similar.
2. Why no overheating?
3. Why no chocolate milk on the dipstick?
4. About how much should installation of the new head cost?
5. What else should be done while the head is off? New head gasket, thermostat...anything else?
6. I'm going to have to drive it out of the city 30-40 miles to get it worked on. Anything I should do beforehand to prevent further damage?
7. How do the Jeeps generally fare after replacing the head? I have no idea how long it's been driven like this since I just bought it, so the vehicle history is not really clear to me. Hoping it can still last a while though, especially with this immediate investment I'm going to have to put in.
1. 2000-01 had a casting defect in the head leading to a tendency to crack if overheated. Again run a search on 0331 head for more info, on top of this 4.0Ls aren't known for blowing head gaskets. This defect was corrected in 2002 so an 02+ head from a WJ (GrandCherokee) or TJ (Wrangler) is an acceptable replacement, or go with buildin1XJ's suggestion of Clearwater cylinder heads, these are even better but of course cost more than a junk yard head.
2. If the crack is small and there is still coolant in the cooling system, it may not overheat, you likely caught it at a good time before it did any real damage.
3. see #2 it takes allot of coolant to make 6qts. of oil milky, but the oil cap being on the head is exposed directly to the area where the oil/coolant mix is occurring.
4. At a shop about $500 + the cost of the head, if you choose to do it yourself it is not that difficult but is time consuming (budget at least a day if you've never done it before).
5.Gasket (head, valve cover, and intake/exhaust of course), Thermostat, rad hoses, might as well do the water pump while you're at it, and make sure the whole system is thoroughly flushed, if the radiator is plugged with crud or leaking have it replaced as well.
6.Change the oil, just use cheap oil and change/have it changed after the head is replaced, it is unlikely enough coolant will leak into fresh oil to contaminate it to the point where it can no longer protect the bearings in 30-40 mi.
7. As long as there is no bearing damage and you use a good head (not another 2000-01 0331) you should be fine, the 4.0L I6 is extremely reliable for the most part, but the 0331 head in 2000-01 is a known issue, a crack usually occurs after an overheat and you never know if a used vehicle has been overheated. It can also take a long time after the crack has occurred for the symptoms to occur, it starts as a tiny stress fracture and continues to grow over time.
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Unread 12-12-2012, 04:16 PM   #7
dropkicksam
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Awesome, thanks for all the info - really great stuff. I'm aware of the head problem, was just wondering why no one seems to consider head gasket - seems cracked head is just way more likely on the 00-01. I'm feeling a little better about it all now, just probably not good enough to do it myself unless I manage to find a really comprehensive and detailed walkthrough.
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Unread 12-12-2012, 04:23 PM   #8
dmill89
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Quote:
Originally Posted by dropkicksam View Post
Awesome, thanks for all the info - really great stuff. I'm aware of the head problem, was just wondering why no one seems to consider head gasket - seems cracked head is just way more likely on the 00-01. I'm feeling a little better about it all now, just probably not good enough to do it myself unless I manage to find a really comprehensive and detailed walkthrough.
That's pretty much it. It generally takes allot of abuse such as repeated overheats to blow a head gasket on a 4.0L I6, where as a 0331 head can crack with a single overheat, so it is extremely uncommon to find a blown gasket on a 0331 head since the head will usually crack before the gasket will fail.
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Unread 12-12-2012, 04:31 PM   #9
buildin1XJ
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DMill89 above is correct about all he said.The 2002 and above heads were cast stronger by a Brazillian company and those heads will have embossed letters TUPY under the rocker arm cover.The ClearWater head is stronger however and will run slightly less than 500$ completly new and shipped to your door.I would not take the chance of driving it one more mile have it towed or rent a U Haul tow dolly and take it to the repair shop.I myself have bought many 2000 or 01 models that were knocking badly from the bottom end with no sign of coolant in the oil but signs of it under the oil filler cap.If you do not hear any clatter from the bottom end presently you may welll have caught it in time.I would also suggest a complete coolant flush as the PO may well have used some type of sealent in it to mask the problem till you got out of his driveway.
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Unread 12-12-2012, 04:35 PM   #10
buildin1XJ
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Pretty Sure JeepKid on this Forum did a pretty good right up thread on the head swap.
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Unread 12-12-2012, 05:26 PM   #11
tjwalker
It's the crank sensor!
 
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buildin1xj has a lot of experience with this issue; his information is spot on.

If you want to read a thread that I think probably has the most comprehensive information on the 0331 head problem, here you go. Good luck!

http://www.jeepsunlimited.com/forums...d.php?t=391831

I'm a big fan of Clearwater Cylinder Head for new heads. They have helped hundreds of unlucky 0331 head owners.
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Unread 12-14-2012, 01:23 PM   #12
dropkicksam
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Think I got some visual evidence of the cracked head taking some pictures through the oil cap. Can someone please confirm? I think it shows most clearly in the first two. Thanks!
img_7990-003.jpg   img_7996-003.jpg   img_7998-003.jpg   img_8000-003.jpg   img_8001-003.jpg  


Last edited by dropkicksam; 12-14-2012 at 08:20 PM..
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Unread 12-14-2012, 01:56 PM   #13
Millermagic
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What is that a picture of?

There's definitely some evidence of the "milkshake".

I'd get a new head on there and not drive it until then!
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Unread 12-14-2012, 02:30 PM   #14
dropkicksam
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That's looking down at the head through the oil cap
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Unread 12-14-2012, 04:13 PM   #15
tjwalker
It's the crank sensor!
 
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Please resize your pics.
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