Remember The Jeep That Overheated 20 Minutes After I Sold It To A Nice Lady? Well, Its Engine Suffered Severe Damage

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This sucks. It really, really sucks. I’m selling what I consider the perfect example of my favorite Jeep — a 1991 Jeep Cherokee XJ Laredo five-speed 4×4 — for one main reason: I’m tired of working on it. So it’s pretty absurd that that, after I sold it, I’m now covered in grease, tearing into the vehicle’s broken engine, whose cylinder head I just took to a machine shop to be diagnosed. What the machinist found was not good; let’s have a look.

I have so much regret. I should have taken the XJ on a long-ish test drive before selling it, because I know I would have noticed a thermal issue far before the engine overheated. The buyer — like most people who expect their cars to, you know, work — did not, and continued driving until the Jeep literally spewed steam out of its exhaust pipe and would no longer start. The result of my inaction is that, instead of just replacing a water pump in two hours, I’m rebuilding the top end of an engine. Actually, to be more precise, I’m replacing it.

This last part is news I just received from my machine shop, whose kind, towering, heavy-set foreman called me earlier today to say only two words: “It’s cracked.”

To be honest, I already knew this was the case. I have owned four Jeep Cherokees in my lifetime, and have cracked cylinder heads on all four of them. I even once wrote about how, while traveling through Colorado, I stayed an extra week to fix my best friend’s family’s XJ, whose engine, I’d been told, was drinking coolant. That ended up being a cylinder head crack as well. (Its crack is shown at the bottom of this article).

As great as the AMC 4.0-liter engine is, that long cast-iron head is unforgiving when subjected to high temperatures, and given that the Jeep Cherokee XJ was designed initially to cool only a 2.5-liter, 100 horsepower inline-four and a 2.8-liter, 110 horsepower V6, its engine bay isn’t exactly ideal for the 190 horsepower fuel injected straight six. The short, wide radiator, along with its two tiny fans (one mechanical, one electric) are just not enough to reliably keep the Jeep cool in a variety of conditions, especially if the cooling system parts aren’t in tip-top order.

Obviously, in this case, the problem had less to do with the XJ’s marginal cooling system and more to do with a water pump that leaked out all the coolant, but my point is that I’m tired of replacing 4.0-liter heads. I’d rather do just about anything else at this point.

Usually I snag a new head from O’Reilly Auto Parts for about $400, but because my donor vehicle for my $350 red overlanding Jeep was a rusted-out Green ZJ with a good motor, I’ve had a spare sitting in my garage for a number of months. I zipped its cylinder head off and took it to the shop today to be checked and shaved perfectly flat; I have no doubt it will be crack-free based on the condition of the 205,000 mile engine (it’s remarkably good).

Now let’s get back to that cracked head.

Here’s a look at the crack that the shop identified:

That’s pretty substantial; I mean, the fact that it’s clearly visible to the naked eye, and that it’s over an inch long tells me that this engine got very, very hot.  What I find interesting is that the crack propagated between two cylinders; my previous experience with a cracked 4.0-liter head in my friend Bobby’s Jeep involved a crack forming between two valves of the same cylinder:

What a nightmare scenario for all involved, really. You sell a car after spending years replacing its entire front suspension, front fender, fender flare, fender liner, rear bumper, front bumper, driver’s seat, ECU, power steering pump, front axle vacuum disconnect motor, radio, and on and on — you’re certain that finally, after all of those fixes, the car is worth enough to be sold for at least a small profit. You didn’t buy it to sell it, of course; you wanted to keep it forever, but it’s been too much of a hassle, and now just want it out of your hair. Then finally, you find a buyer, who drives away and then 20 minutes later — boom: You’re stuck fixing the Jeep yet again.

I truly believe that, if a car has been unreliable enough, it will feel like it’s betrayed you, and you’ll fall out of love with it. That happened long ago between me and what I once thought was the most perfect Jeep on earth. I want it out of my life.

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87 Responses

  1. I think you just have bad luck man. I am on my 4th XJ as well and none of them have cracked the head, even the 2000 I had. And the 2000 was the one that the lower radiator hose broke and it did overheat!

    1. Seriously… to say this XJ is the perfect example is a major stretch. It’s rusty and has a cracked head, it’s filthy on top of that, needs tires, who knows what else.. it’s a mess. It’s fun to watch someone wrench on cars that should otherwise be in a junk yard thought. The entertainment value is pretty high.

  2. I’ve always thought the I6 to be incredibly tough, but now I am a bit worried about my own as twice in its 21 years of existence, it has overheated as the electric fan cut off and I didn’t notice until the it beeped at me and told me to look at my gauges. There was also a period when it was running between 210-220 for years…should I pull the head and get it inspected. Running great currently but would hate to get stuck somewhere! Currently consistently runs around 200 or less and isn’t drinking coolant so hoping it’s good!

    1. No, just send an oil sample to Blackstone. They’ll tell you if coolant is getting into your crankcase (that’s how I learned on two occasions after noticing a SLIGHT increase in oil volume on my dipstick).

      The XJ’s achilles heel is that crappy little electric fan, which is REQUIRED in order to keep the engine cool. ZJs (which I prefer if equipped with a non-Chrysler transmission) just need one mechanical fan to stay cool.

      Modern cars use electric fans, but I get the impression that they’re built to last longer than an XJ “auxiliary fan.” Also, if they stop working, you’ll be notified, and the car will go into limp mode.

      XJs are just too easy to overheat.

      1. Thinking that something like this should be on your radar. If done right, this should be a massive improvement in cooling ability.

        I know, you love parsimony like you love Jeeps. But sometimes if you spend more up front, you end up saving long-term.

  3. David – sometimes when we’re angry or hurt, we say things we don’t mean to the ones we love. You just need to take a deep breath, go for a long walk, and cry some [rusty] tears. You were made for each other. Everything is going to be alright, man.

    1. There’s always someone trying to keep an abusive relationship going. Next you’ll tell David that he can’t do any better than this demon Jeep, and that the neighbors will start talking about him if he doesn’t keep up appearances.

  4. Ironies abound. My friend *gave* me his Scott”s (by John Deere) lawn tractor because (he said) he didn’t want to work on it any more. (He”d just bought a new one.)
    Then he proceeds to help me drop the mower deck so he could weld its several major cracks.
    (Do I owe him, like, a beer or sumpin?)

  5. I feel your pain David. A big part of the reason I love your stories is because I can’t relate to them so very well. I’m sure others feel exactly the same.

    In other words, you are not alone. Keep on persevering.

  6. I feel your pain, I had a E39 BMW 528i. I really liked it at the start, but by the end I just got sick of the way it burned through a litre of oil every 1000kms, all the little plastic parts in the engine bay kept breaking, every service would cost me at least $2000 with all the things that kept going wrong. I hated it by the end.

    1. Wow, exactly mirrors my experience with my first “nice” car that I got…. 2003 530i. I though I was out of the woods by getting the final model year of a popular model… nope. Loved the driving experience so much and even to the end I’d be amazed how no other car compared the BMW’s solid feel and buttery I-6.

      But the endless leaks and malfunctions and random plastic parts crumbling during every repair and replacing parts which don’t even exist on normal cars made me realize that every time I drove it, there was a subconscious fear of “what’s next on the list to go”.

      In my case the money wasn’t even the main issue since I did all the work myself… it was the prospect of yet another evening/weekend sacrificed to the god of BMW cost cutting that made me realize it was time to move on. Still felt a pang of regret watching it drive away, but it was certainly the right decision after 10 (!) years and 110K miles.

  7. Ugh, it’s like a relationship (human one, not a car one) going south. You put in the work then one day the effort outweighs the benefit but it took too long to figure it out. Look at all those half finished project cars in the world! So many of us have been there.
    On the flip side, that’s why these car culture stories can be so endearing, you can feel the resolve of someone who just got it right, and got a bit lucky too. Fills me with automotive hope.
    I’m sorry you had a bad one, and once you clear up that fleet, maybe you’ll love the next one more. Or not, but you’ll know it a lot quicker.

  8. “I truly believe that, if a car has been unreliable enough, it will feel like it’s betrayed you, and you’ll fall out of love with it.”

    My brain and the permanent rose-tinted memories of my 1989 Renault Espace From Hell would beg to differ.

    Just yesterday I was picking my daughter up from school and somehow the Espace came up. She’s only 8 so she has no memories of it, but she does ask about it a lot (the engine died when my daughter was 2). This time she was surprised that it was a Renault – maybe because I always refer to it as “The Espace”. At some point I just said that if we got crazy rich I’d be driving to France to buy the best looking Espace Quadra MK1 for sale (but let’s not fool ourselves, if that was to happen, I would not do that trip to buy *just* the Espace).

    1. Ahahaha, my daughter has a similar relationship with my old Volvo 245 – which I crashed, falling asleep on the highway (grad school) the day before her 2nd birthday. When she wants to punish me she will draw a picture of a Volvo on fire for me.

    2. I would like to take a moment to talk to you about Renaults. I have two 4CVs and need parts. I have NEVER owned French cars before and am running into serious roadblocks in getting parts for them from companies that will actually ship to the U.S. Can you point me in a good direction for those? I’ve joined forums but they are slim pickins when it comes to info for North American customers.

      Thanks in advance!

      1. I’m interested in a good US source for Renault parts, too, in that my Volvo 66 GL (a.k.a. DAF 66) uses a Renault Cléon-Fonte engine and I haven’t had much luck with finding anything locally, except in the sense that the 66 GL parts car in my driveway is local.

  9. The most surprising thing in this article is that David has owned four Jeep Cherokees.

    That number seems way low considering the amount of ‘holy grails’ that have been through the mud pit in his backyard.

  10. Personally, it is my opinion that the reason the Jeep Gods have subjected you to so many cracked 4.0 heads, is that you are being gently nudged to build a monster 4.0L with an aftermarket Edelbrock #50169 performance aluminum cylinder head. You should listen to the Universe. It knows what’s good for you.

    1. A Stellantis cooling engineer that keeps running 4.0’s behind that deficient radiator? Nah, that’s not the hint he’s been ignoring. He needs to nerd out, come up with a better cooling system for these that can be implemented cheaply, and market the damn things as XJ by DT cooling systems or something. Make a few bucks and keep a lot of Jeeps on the trails.

    1. No, he needs to go deeper. David, get in touch with your german heritage and buy BMWs.

      I can guarantee that even a base-spec E46 will never stop giving you wrenching opportunities. Plus you get an excuse to buy yourself a whole set of Torx bits (good for electronics repair too).

      1. He is fond of the mk1 Audi TT, we can probably start a pool of readers at a buck a piece and find the most rusted out quattro in north America and just drop it on his lawn and see what happens.

  11. Hot take coming.

    This is not your fault. This is/was the new owners fault. I would have told her to pound sand, but I understand you are a bit of a public figure at this point, as anyone looking to get into having hobby vehicles NEEDS to know how to keep them in good condition; there were no idiot lights back then. She found that out the hard way. I think you should charge her something for the repairs. It was under her watch and she destroyed it. I’m all for being nice. But part of being nice is not rewarding stupidity. We must reward being smart. She was not smart. She was dumb and couldn’t watch the gauges she needed to while driving a vintage vehicle. But she’s going to be rewarded with a rebuilt head. The circle of stupid continues.

  12. Just for the record: I have been a friend of The Nice Lady for over 30 years and she is perhaps not actually divine, but a goddess of the more human sort, and thus deserving of the benevolence and karmic right-making David is heaping on here.
    All kudos to David for being a stand up guy (from the initial meeting with TNL) and all subsequent transactions, and the universal scales of justice and whatnot do level off.

  13. Hey David!

    Been watching this, and I have one fear that I will share…….and possibly (likely) piss you off to consider.

    If the engine got THAT hot, by those cracks and Rootwyrm’s explanation, this baby got hooooooooooottttt with a capital F, hahahaahahah. What’re the odds of the piston rings losing their temper?

    I ask, because I have had this happen a handful of times over the 30 odd years I have been working on cars. It’s not often that it occurs, but it does seem to happen when you give one a real through nuking.

  14. Real mechanic would have drilled and pinned that crack, heated the head up in the oven in the rental house, Welded it with the battery DC stick welder and then smoothed out the weld with a flat file

  15. Idk if I’d call a cracked head “severe engine damage” if everything else is fine. Cool you had a spare. Weird about the location of the crack; I don’t get how that can happen either.

  16. Yes XJ’s through their design mis-steps were built to overheat, I finally cut ours up to take a YJ radiator and mechanical fan. So far so good but if that doesn’t work it’s getting a V6 so at-least the wall of acc’y components is back a little bit.

  17. “I truly believe that, if a car has been unreliable enough, it will feel like it’s betrayed you, and you’ll fall out of love with it.”

    I’ve had this feeling towards my RAV4 a couple times now, and yet when I take it for ‘one last drive’ I think “this is far too nice to get rid of” and then spend a bit more money on it to keep it going.

    Now excuse me while I go order a brand new fuel tank from Rock Auto…

  18. “To be honest, I already knew this was the case. I have owned four Jeep Cherokees in my lifetime, and have cracked cylinder heads on all four of them.”

    These vehicles are garbage. 100% engine failure rate on any personal fleet is not normal.

    1. I’m also very confused by “the unkillable 4.0” statements, when time after time they are proven absolute garbage.

      This is coming from a guy who has owned lots of Alfa Romeos, a couple Fiats and a whole bunch of Citroens and VWs and has never been stranded or experienced an engine failure in any of them.

  19. Fell your pain here. Yet, every time there has been an overheat on any car I’ve worked on is, 9 times out of 10, that the head gasket failed and/or the cylinder head cracked. Really doesn’t matter if its an iron or aluminum head. One car in particular, the heads were fine after being checked, later found a cracked cylinder wall. My favorite was discovering a cylinder sleeve in a 1.9 Saturn had actually dropped down in the block causing coolant and oil loss. Every 4.0L I have diagnosed that has overheated, the head was cracked.

  20. Long ago I sold a Fiero to my girlfriend’s Dad. A few months later, while putting a new (used) Iron Duke into it, I decided to never again sell a car to someone I know. David, you’re a kind and honorable man. Too kind.

  21. There’s no way that’s the only crack, or that it’s solely heat damage on this one. That’s… deeply concerning for that specific head. Once the shop found that one, the head was already condemned, and I would absolutely not attempt a weld on it. That’s through-and-through; too much risk of not getting good penetration toward the center. (I’m sure they already said as much.)

    There has to be a secondary internal crack though. Fact is, no manufacturing process is perfect, mistakes happen, things randomly fail. But the position of that crack at 3-4 is exactly where I expected and also exactly not where it should be. The bowing exacerbated it, no question, but that crack had to already be there.
    It’s really simple: go look at the other cylinder head you posted in this article. Note the location of the crack – it’s at the valve seat area. Which is one of the hottest areas of the cylinder head, with the least coolant flow. Now, look at the head that failed in this case. The crack is actually through a coolant channel – the coldest part of the head. Simple overheating wouldn’t have caused that, because it STILL would be one of the coldest parts of the head with coolant boiling off. And bowing of the head obviously compresses the metal at 3-4. That’s more like a separation from pull.
    Just about the only way that happens is if you already a void, microfracture, or similar defect or failure in that exact spot already. And it then got blown wide open. Otherwise you’d have something more similar to the second head you posted. You’d expect a stress crack at a point of higher stress.

    And of course, it STILL doesn’t explain cylinders 5 and 6. Let’s assume for a second that the crack was present and was leaking. Coolant would be going into cylinders 3 and 4 with low compression, resulting in misfire. But nope. Didn’t have that. So we have to assume a typical silent head crack in sealed area. Well, that’s the key point – it’s in the sealed area.
    (Look, can I get like special permissions to post illustrations or something? That would be so much easier. Anyway.)
    Look closely at the head gasket. You’ll see that between the fire rings and coolant channel, there’s an usually an additional sealed off area which has additional holes in it. (It varies by head gasket manufacturer. I recommend Fel-Pro MLS personally.) That setup means that where the crack is located would generally be in the secondary sealed area, which drains to the front or rear coolant passages.
    https://www.cleggengine.com/media/catalog/product/cache/7bd10f723b854a7346d165f731f91370/4/3/43e78083f8c0a79ff0bb5a7a46af4773.jpg
    (Seriously, let me post multiple URLs at least!)

    So then 5 and 6 could be explained by a failed fire ring right? Wrong, because 5 and 6 had good compression! Head gasket wasn’t failed there. If it was failed and not damaged in removal, it was at 3-4. So yeah, this is REALLY bugging me. I mean obviously the head is already scrap. It possibly could be repaired but it’s almost certainly not economical. And it’s making me really bloody curious as to what the hell was really going on.

    I really think you should keep that head and learn you some NDT (Non-Destructive Testing) in depth. I bet if you reach out to the folks at Magnachek (they have a location in Madison Heights,) they’d be happy to do some press with the Autopian and educate folks on the various NDT processes.

      1. I mean, who doesn’t love magnets measured in Teslas and high powered X-rays? (Don’t stand over there unless you never want to have kids.)

        At this point though, I have a feeling it’s cracked up in the guides on at least #5 and #6, and possibly up on #1 and #2. There’s just got to be something dumping water into those cylinders. Up where you just can’t see. Might even be pinholes or something. It’s just bizarre that it’s dumped THAT much into the block with absolutely no symptoms.

  22. God I am glad I did not buy that thing. I didn’t need an XJ I couldn’t drive in winter because it was too nice.

    That said, I suppose I would probably have noticed the overheating right away, but still.

  23. The buyer though…she’s gonna get a good deal out of this debacle. New head/valve job, refreshed cooling system, that’s really several XJ issues out of the way, honestly. Sure, maybe she could invest in a custom aluminum radiator; I’ve done that with good results. The only major thing left to worry about is “death wobble,” but that may be a ways down the road.

    And David, you got several articles out of it. Reminds me of all the unwanted work I had to do on my kid’s ’91 XJ, but it was worth it in the end.

    1. It’s REDUCING the fleet that got me into this mess, Shop-Teacher. Had I not decided to sell it, I’d have driven it, caught the leak, and swapped the pump. I’d be cruising to the hum of that glorious straight six!

        1. The AMC Six is pretty much bulletproof if it’s properly cooled.

          As David pointed out, the XJ was designed for an inline-four (same basic engine, minus two cylinders) or a GM-sourced V6, both of which had considerably less mass to cool than the Six. Of course, Jeep did the math and determined the existing radiator was (just) enough to do the job when they opted to install the bigger engine and didn’t bother to upgrade.

          The moral of the story is to pay attention to the temp gauge and maybe consider upgrading the radiator if you live in a hot climate.

          I once had a shop in El Centro, Calif., build one for me from scratch for my old Scirocco. They specialized in building upgraded radiators because the stock ones in most new cars just couldn’t’ handle the desert heat. The one in my VW worked so well that I ended up disconnecting the electric fan so I’d have a heater when I returned to Seattle.

              1. LOL

                I got a Mk7 GTI with a stg2 tune that lives its life at the red line under 30+ psi of boost as my track car.

                It’s at 65k miles right now on the original turbo and zero oil consumption.

                The TSI is not your dad’s mk5 🙂

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