How worried should i REALLY be

Ill try to make this quick. I just bought a 2000 xj sport 127,500 miles, in awesome shape in and out, easily the smoothest best running xj ive ever driven and i drive them all the time having a 97 and 98 previously. I am currently in school to become a chrysler technician and have been doing it for a year, general mechanical work for about 6 years. Anyways ive learned from the veteran techs about the 0331 head issue as they crack and ruin the engine if not caught early etc. This is the first car ive really spent some good money on and so naturally im a little nervous and worried, i did a complete inspection after i bought it and noticed coolant on the valve cover by the bolts. traced it down to the upper radiator hose by the clamp, very small cut but the reservoir was 3/4 under full. replaced the hose yesterday and properly refilled the cooling system. never goes over 210 even with the old hose. Basically im torn because on the forums, ive seen nothing but "its not if, but when" these heads crack, and overall a negative look at these two years of xj heads. All of the technicians who have worked on these since they were new have told me almost the opposite, they said it is somewhat rare actually, and that most of them happened in the first 60k and after that as long as you maintain the car like you should, it should be just as reliable as any other year xj. Getting to my main point, How worried should i be? i know all about warning signs and i havent honestly had the car long enough to fully see any of them but id like to just get some opinions to my situation

I've overheated the crap out of mine and as of et have no signs of head cracking.

I too read all the doomsday threads on 0331 heads.

I too worried.

I so far have no indication it's happened to mine.

It happens, it happens to 0331s more than others, it doesn't happen to everyone.

So basically it's not a problem until it's a problem.

Watch your oil, if it gets milky you're changing a head. If you're really concerned you can send off an oil sample and check for presence of coolant.

If none of the above is the case then you are fine. No matter what, an internet forum cannot crack your cylinder head.

yeah thats basically the only conclusion that can be made. oil is golden translucent brown, not milky whatsoever, coolant is bright green. im just going to have to be one of those guys who treats their xj like goddess when im used to beating the crap out of them. on my first one i drove the sh*t out of it for 120k miles with absolutely no service other than 3k oil changes an a/c compressor, water pump and t stat and brakes.

The external coolant leak you found would have nothing to do with a cracked 0331 head. The crack is internal to the head and happens between cylinders 3-4 where there is a known casting defect.

Now that you have the coolant reservoir at the correct level, just keep an eye on that level.

As you now own a 2000, you should check the coolant level every week at the very least. Commit this next sentence to memory. The #1 symptom of a cracked 0331 head is "unexplained coolant loss".

Will all of these heads crack? Absolutely not. But you have been misinformed by your technician friends. The 0331 head can crack at ANY time, any mileage. Poor cooling system maintenance and for sure any overheat will greatly increase the odds of cracking the head. But that said, I've seen vehicles that have been meticulously maintained have the head crack. And I've seen others go to 300k with no crack. A lot of it is luck, pure and simple.

That is why you keep an eye on coolant level. Takes all of 1 minute. As long as you do that, you'll be fine. If you catch it soon enough, you swap out the head, perform a few back to back oil changes and you will be okay. Relax and enjoy your XJ!

Since you already bought it - keep an eye on it, keep a bit of cash in an oh-crap account (you should be doing this anyway... good life choice) and a list of part numbers you need on hand.

Keep an eye on the oil, check the dipstick and oil cap for milkshake occasionally, maybe every few oil changes send some to blackstone for an analysis. Other than that? Run it.

The only time I recommend against a 2000/2001 is when someone is looking at one and not sure or the price is high - mostly because 99s are cheaper (because most people see an older car and say it's worth less), better in every way, and known to not have the problem. They're not massively better in any single way, but if you don't own the car yet, you might as well choose the best, right? Unless the price on a 2000/2001 is low enough to make it a better deal.

@birchlakeXJ
just to clarify these are 20-30 year certified chrysler master techs at the top grossing dealer (service and sales) on the west coast.. they do know what they are talking about. but i do also realize the fact that anything could happen. and that being said the coolant bottle will get checked every 2 days. im going on about a 300 mile trip tomorrow over a mountain pass. supposed to snow up to 3 feet tonight and another 11 inches tomorrow which is unheard of for washington state. so not only will the engine get a nice workout but the 4x4 system as well. Im excited!

@kastein
Ya i already bought it, its getting ridiculous finding a good xj around here now so i jumped on it. i had some throwaway cash for a down payment so im only financing 4500 on it which is trade in value so im good in that respect. If i do have to replace the head a remaned unit is pretty cheap plus its a fairly easy repair other than the head being 84lbs

Sorry dude....anybody that tells you that you're safe after 60k with the 0331 cylinder head is sadly misinformed. No offense intended to your technician friends.

Keep an eagle eye on your coolant level. It will tell the story. I have a lot of experience with this issue.

Here is a link to a very comprehensive thread on the 0331. Required reading for anybody that owns an 00-01. It is good homework; knowledge is power.

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

they didnt say i was safe, they just said they saw the majority of failures happen before 60k

dachacho said:

they didnt say i was safe, they just said they saw the majority of failures happen before 60k

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That is probably because jeeps with over 60,000 miles are rarely worked on at a dealership.

I would watch out for any signs that any cylinders are running lean. Check the spark plugs periodically, or run and OBD-11 live data scan regularly to look for odd fuel trim or O2 sensor issues, that might let any one cylinder run too lean. Keep a close eye on the manifold, check for glowing exhaust at night....stuff like that, might give an earlier warning before the head cracks.

Ecomike said:

I would watch out for any signs that any cylinders are running lean. Check the spark plugs periodically, or run and OBD-11 live data scan regularly to look for odd fuel trim or O2 sensor issues, that might let any one cylinder run too lean. Keep a close eye on the manifold, check for glowing exhaust at night....stuff like that, might give an earlier warning before the head cracks.

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On my 2001 XJ I have a couple of cylinders that are running rich (the spark plug insulators are black almost up to the tip) and haven't figured out why. My plan is to check the 2 precat O2 sensors to see if they are "lazy", but after that I'm pretty much clueless. Suggestions?

HappyDog said:

On my 2001 XJ I have a couple of cylinders that are running rich (the spark plug insulators are black almost up to the tip) and haven't figured out why. My plan is to check the 2 precat O2 sensors to see if they are "lazy", but after that I'm pretty much clueless. Suggestions?

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Which spark plugs are you using?

HappyDog said:

On my 2001 XJ I have a couple of cylinders that are running rich (the spark plug insulators are black almost up to the tip) and haven't figured out why. My plan is to check the 2 precat O2 sensors to see if they are "lazy", but after that I'm pretty much clueless. Suggestions?

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Isolated plugs with an issue will not be an O2 sensor issue. It will be leaking injectors or weak spark (rotor, cap, wire, or coil pack) or a bad spark plug, or a compression problem or oil valve seal leak problem. Are they dry powdery black or wet black?

My 2001 XJ's 0331 Cylinder Head cracked @ ~ 120K miles... so it can happen or not happen at any later mileage. Mine was in part due to a really clogged and poorly functioning cooling system. My radiator was SO clogged I don't know how any coolant got thru.

Mine was purchased 2nd hand (or more) thru a dealership that had got it in as a trade. Looked GREAT on the outside, but had apparently had NO service done on it during it's life. The chance you take on a used vehicle.

Anyway... like it's been mentioned here, unexplained coolant loss is the first sign, but be sure and do a quick oil change and get that analyzed if you are experiencing continued coolant loss. Could be the 0331 head crack is few and far in between, however I had it happen to me and I'm a freak about maintaining our vehicles.

cruiser54 said:

Which spark plugs are you using?

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Champion

I'm sorry, I'm dragging this thread off-topic. How do I fork to a new thread?

Ecomike said:

Isolated plugs with an issue will not be an O2 sensor issue. It will be leaking injectors or weak spark (rotor, cap, wire, or coil pack) or a bad spark plug, or a compression problem or oil valve seal leak problem. Are they dry powdery black or wet black?

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I didn't know whether the engine controller looked at the Bank 1 O2 to adjust the fuel/air ratio of cylinders 1-3 and the Bank 2 O2 sensor for cylinders 4-6, or just lumped them together to adjust the ratio for the whole engine.

No rotor, cap, or plug wires on a 2001.

After I wrote the question I also thought I should check the coil pack because the rich-running cylinders are adjacent to one another. I'll try swapping the packs and see if the rich-running cylinders move with the pack.

I'll have to look at the spark plugs again to be sure which cylinders are running rich -- I think it is 1 and 2, but my memory is a fleeting thing.

Dry or wet? I'll have to pull the current set to see. I replaced the previous set after only 8000 miles to see if I could rid myself of a intermittent miss that is becoming more frequent. I did keep the previous set so I can tell which cylinders are running rich, but they surely have dried out by this time -- unless it was oil.

Thanks for the suggestions!

birchlakeXJ said:

The crack is internal to the head and happens between cylinders 3-4 where there is a known casting defect.

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Its not really internal to the head. Yes, the head cracks, but it cracks between #3 and #4 external to the head. If you pull the valve cover off you can see the area where the crack would be/is.

As you now own a 2000, you should check the coolant level every week at the very least. Commit this next sentence to memory. The #1 symptom of a cracked 0331 head is "unexplained coolant loss".

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Not a great indicator. It can weep ever so slightly that you won't notice until its too late. If you are at the point where you are noticing large amounts of coolant missing your bearings may already be toast.

HappyDog said:

Champion

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Replace them with NGK. 00+ engine really like the NGKs better.

HappyDog said:

I didn't know whether the engine controller looked at the Bank 1 O2 to adjust the fuel/air ratio of cylinders 1-3 and the Bank 2 O2 sensor for cylinders 4-6, or just lumped them together to adjust the ratio for the whole engine.

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On teh cali emission package with 4 O2 sensors they trim the banks based on the O2 sensors for each bank.

After I wrote the question I also thought I should check the coil pack because the rich-running cylinders are adjacent to one another.

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thats not how the coil pack works. The coils aren't firing plugs next to each other. One coil fires 1 & 6 at the same time, 2&5 at the same time and 3&4 at the same time. If they are adjacent to each other its probably the O2 sensor or something fuel related.

Talyn said:

thats not how the coil pack works. The coils aren't firing plugs next to each other. One coil fires 1 & 6 at the same time, 2&5 at the same time and 3&4 at the same time.

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I am not sure why that is relevant to a crisscrossed 1 & 2 missfire?

Ecomike said:

I am not sure why that is relevant to a crisscrossed 1 & 2 missfire?

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He said the plugs are adjacent, so he thought here could be a problem with the coil rail. The coils are not divided like that in the rail. If there was a bad coil it wouldn't produce weak spark on adjacent cylinders.

Talyn said:

He said the plugs are adjacent, so he thought here could be a problem with the coil rail. The coils are not divided like that in the rail. If there was a bad coil it wouldn't produce weak spark on adjacent cylinders.

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Well I have not seen or worked on one of these, so I am no expert, but I was suggesting that the wires could be criss crossed, 1 on 2 and 2 on 1, and he seemed to confirm that was possible even on the coil packs? I was not thinking of a bad coil at the time, but a criss cross. Is that even physically possible?

Do these even have wires, or just a coil on the plug ends?

Is their one coil pack for 3 cylinders, 2, or one cylinder on the late jeeps?

A bad coil pack sounds like a possibility if it feeds just 1 & 2? But are you saying one coil pack feeds 1 & 6? If so now I get it, I see what you are getting at!!!