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Here’s Why That Jeep That I Sold To A Nice Lady ‘Blew Up’

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“Hey, the Jeep is overheating and there’s black smoke coming from the exhaust,” the nice lady who had just bought my Jeep 20 minutes prior told me over the phone. A few moments later: “Now the Jeep won’t start anymore.” I grabbed my keys and drove 30 minutes southwest to Northville, Michigan to assess the damage to a Jeep that I had been so damn close to finally being rid of. I had nearly taken a step in culling my herd of vehicles, but the Jeep gods struck me down with a mighty blow. Let’s see how hard that blow was by assessing the damage.

Last Tuesday was a nightmare, as you read in Jason Torchinsky’s live blog. It was supposed to be a glorious, rare day in which I actually reduced my vehicle fleet in what has to be the most painfully glacial move towards any goal ever — the goal being me having some semblance of a social life. Look at how happy the buyer, Tracy (whose dad is the Jeep’s original owner) is:

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And look at how happy I am for finally being rid of this Jeep. I’d bought the Jeep in 2018, but soon thereafter knew I had to part ways with it. I realized that I’d get less money for it if it remained broken, so I replaced the dented fender, fender flare, and front and rear bumpers — all of which required paint from my local auto body shop. I also replaced the front axle, steering box, steering intermediate shaft, engine computer, driver’s seat, floor mats, leaf springs, radio, and so much more. In the fall, I finally had the Jeep in a sellable condition — one that would bring me more than just a pittance in profit, and one that would ensure that the Jeep lives on for years to come. Selling the Jeep back to the original buyer’s daughter was a great moment:

Sadly, the moment didn’t last; instead of parting ways with the machine, I experienced a seller’s worst nightmare: Immediate vehicle failure only moments after sale.

I arrived on the scene half an hour after Tracy’s call. Her husband had limped the Jeep into a gas station parking lot, and now it was time for me to see what was up. The first thing that became obvious when I popped the hood: There was coolant all over the engine bay. The motor was bone dry on the inside, but dripping wet at the front:

Tracy had told me the motor had been struggling to fire up; this concerned me. After checking the oil (it looked clean), I cranked the key over to see what was wrong. What I heard nearly made me weep; the AMC inline-six engine was crying in pain:

How had this happened? How had this motor developed a severe knock? I had changed the oil a few years prior, but I hadn’t driven the Jeep. Had moisture gotten into the crankcase in the interim? Surely not that much moisture would get in from sitting, right? Had I accidentally left automatic transmission fluid (which I use to protect cylinder walls against rust) in the cylinders when I threaded in the spark plugs? And did this cause me to hydraulic the motor and bend a rod? I racked my brain for days as I tried to get AAA to tow the Jeep, only to be turned down because the company couldn’t find anyone to yank the Jeep a measly 29 miles. These are weird times we’re living in.

When the local police department called to notify me that it was placing a 48-hour notice on the Jeep and that if I was unable to remove it it’d be impounded, I made removing the vehicle (about which I had notified the gas station owner, for the record) my top priority.

I bugged AAA, and eventually gave up when the company told me it just couldn’t find a way to tow my XJ back to my place. I reserved a U-Haul trailer, and planned to yank the vehicle back to my place on my own. But then a tow truck driver called me unexpectedly, I convinced him to wait 30 minutes for me to arrive, and finally the Jeep was on its way back to my place.

Getting the motor started after the tow truck driver dumped the Jeep in the street in front of my house was difficult, but after the driver hopped in and cranked the key with the gas pedal down, the depressed iron lump sputtered to life and slowly powered the off-roader into my driveway.

Assessing The Damage

Yesterday, after nearly a week agonizing over it, I set about determining what the heck had happened. I was baffled because the AMC inline-six engine in this XJ is supposed to be unkillable. In fact, its durability is a major tenet of my religious views, and just on my philosophies in life. How this motor just failed like that for apparently no reason? Would I need to seek salvation elsewhere?

I was shook.

The first thing I did to get to the bottom of this was change the Jeep’s oil, figuring there would be significant metal shavings/bearing bits in it and the filter. Strangely, the 10W-30 that drained from my pan looked clean, and so did the inside of the oil filter. How could the main or rod bearings fail but not produce significant wear particles? That didn’t make sense to me. I poured in clean oil and fired the Jeep up to learn more.

Again I was greeted with a harsh, metal-on-metal knock. Confused, I decided I wanted to let the car idle for a little longer. Since I didn’t want to risk damaging the motor, I poured some coolant into the radiator, replacing what had billowed out during the overheating incident. Unfortunately, everything I poured in flowed straight back out onto my driveway. The source of the leak? The water pump.

I fired the engine back up, and kept an eye on that pump pulley — it was wobbling all over the place! I listened closely, and it appeared that this was the source of the knock! I’d never seen a water pump that loud before; I assume the bearing got so bad that the impeller on the back side of the pulley was hitting the engine block.

To test my theory, I used a screwdriver to slip the serpentine belt off the pump pulley; this way the water pump would not spin, since its pulley would no longer be powered by that of the engine’s crankshaft. The result: The knock went away!

This was great news, of course, but there was still a problem: The engine didn’t quite seem to idle as well as I’m used to. So to try learn if the straight-six had been damaged by the high temperatures caused by the failed water pump, I conducted a compression test by threading a pressure gauge into each spark plug hole, one at a time. During the compression stroke of the four-stroke internal combustion engine, the piston rises and squeezes the intake air/fuel mixture; in the case of the 4.0-liter engine, that air/fuel mixture should be squeezed by the piston to between 120 psi and 150 psi.

Sadly, the only cylinders that met the spec were one, five, and six. Two, three, and four all made just 60 PSI of compression, or about half what the engine’s spec calls for. This behavior reeks of a bad head gasket; I assume it failed between cylinders two and three and between cylinders three and four. It’s also possible the head cracked or warped.

In any case, I have to remove the top of that engine to see what happened. It’s going to be a long job, but I’d much rather do it than swap out an entire four-liter motor. Once my head job is done, it’s over ‚ I’m selling the Jeep to Tracy, and whatever happens after that is between her and her Jeep gods. I wouldn’t be surprised if it ran flawlessly for the next decade while not under my ownership.

It seems these Jeeps will do whatever they can to stay with me. Luckily, I don’t think it will take too much convincing to get this XJ to finally just let go; after all, it’s heading south, away from rust.

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66 Responses

  1. Crazy that you had issues finding a tow. AAA picked up my SVX on the left side of 75N in Madison Heights in the snow, and dropped me off in Farmington, no issue. Not sure if they serve as far out as Troy, but I had Hadleys’s towing tow it home from the collision estimate and they did a great job and were reasonably priced. Highly recommend them.

  2. I know this feeling of unbridled elation.

    A couple years ago, I had a 2009 Dodge Ram 1500 with the 4.7 (before they were just RAM). I was a block away from home when I heard it knocking like a Jehovah’s Witness.

    “No,” I replied, “I haven’t heard of your lord and savior Catastrophic Engine Failure, not would I like to become acquainted.”

    I was in the depths of sorrow, certain the engine was lost, the foremost fear of 4.7 owners. After checking it out, I couldn’t find any clues indicating the motor was lunched. Eventually, I found what was looking for: a seepage from the weep hole on the water pump so slight, it didn’t manifest as a puddle under the truck. Having realized I dodged (pun) a huge bullet, I gladly bought the parts for a water pump R&R and rolled up my sleeves.

  3. As much trouble as you had finding a tow, and knowing the number of cars in your possession that lack motive capability, methinks your next purchase should be a Jeep that can safely haul another Jeep from one place to another. Or at least make friends with a local with a truck and trailer…

      1. My Dad worked for then ran a Skelly station in Iowa back in the early-mid 60’s, the guy he worked for and took over the business from refused to do business with AAA. They didn’t want to pay full price for tows, if you could get them to reimburse any of it with 6 months of the job. A lot of stations that towed on the side would just refuse if they were told that the person was going to be using AAA.

      2. Used to have AAA. (key phrase *used to* )

        Called them to assist with the simplest of things; a dead battery.
        Complication 1: Labor Day weekend
        Complication 2: we were camping
        But! campground was less than 15 miles from nearest town with stoplights, gas stations, etc.
        Still AAA could not get it together to send aid. Said to myself (and many within shouting distance) What am I paying for if not to get roadside assistance?
        Ended up jumpstarting from fellow campers rig, and luckily got home.
        Cancelled AAA next day, never looked back.

        Lesson for you other pilgrims: Get your roadside assistance elsewhere; suggest USAA if you can access it – very affordable!

    1. It is. I bought a Legacy GT out of town from an iffy dealer years ago (they aren’t exactly common cars so I had to take what I could get). Got it checked out at a Subie dealer down the road. After a long day of driving and waiting and signing papers, the turbo blew about 5 miles from my house. Dealer told me to go fly a kite and ghosted me.

      Not a fun experience to say the least.

    2. Very true. I have been in this situation. Bought a 2005 Forester XT. It didn’t make the 2 hour drive home. Was a very strange failure. The ring with the starter gear teeth separated form the flywheel. So when trying to start the car the ring would spin and the flywheel would not, thus the engine would not turn over. Got it fixed and have been driving it for 2 years now though 🙂

      1. My OBXT got the low compression bug within a year of owning it, I yanked the POS 255 and installed/tuned a twin-scroll JDM 2.0. To say we got shafted with the 2.5 is an understatement, the smaller engine is a honey compared the the USDM tractor, and absolutely sounds better without unequal-length fart exhaust.

  4. Fingers crossed you can get away with just a skim on the cylinder head.

    Bought a Subaru Brumby for my mum at the start of the year off a farmer who thought it had been overheated as it conked out when he drove it back to his farm from town.

    Went to fire it up and it idled fine but drove horribly. After putting a borescope down the cylinders all looked okay and there was no sign of damage.

    The poor running turned out to just be the carby, now it runs excellent though I replaced the whole cooling system to be sure, including radiator.

    Do you have a borescope DT, if not it might be a good purchase for diagnosing stuff like this in the future.

    1. I believe thats what David thinks. The water pump is quite low in the cooling system, so when the pump failed it allowed all the coolant to run out of the engine. As the heads are at the top of the engine, they will have lost coolant early in the failure and may have overheated more than the rest of the engine. Heads have a tendancy to warp relative to the engine block when they get hot, especially if the head gets hotter than the rest of the block. This can cause a head gasket failure. NOTE: anyone who really knows how this process works, feel free to correct me, just this question was unanswered, so I’m having a stab at it.
      As soneone who once lost all the coolant out of my Mk.2 VW Golf 8v, as the engine temperature sensor is in the coolant, if all your coolant is on the road, the temperature guage may fall to cool. Fortunately I also had an oil temperature guage in the rudementary “computer” display. By the time I remembered this was there and figured out what might be going on, the oil was nice and toasty. As David points out, I took the head to a local machine shop who scimmed it flat, I refitted it with a new gasket and head bolts and the engine ran really well.

  5. “the nice lady who had just bought my Jeep 20 minutes prior told me over the phone. A few moments later: “Now the Jeep won’t start anymore.” I grabbed my keys and drove 30 minutes southwest ”

    You sure were taking your time.

  6. Just had this issue where I was convinced I would be shopping for a new car, only to then find a puddle of coolant had collected on the plastic shielding under the car which eventually led me to the water pump. Volvo 5 cylinder has the water pump tucked down deep in the engine compartment running off the timing belt so I couldn’t pinpoint the sound for the life of me. Spent hours googling the sound and never found a good example until I watched your videos.

  7. Here I was halfway through the story thinking “Hmm, a trip to Michigan for a busted keep isn’t too far. Maybe I could just grab the engine out of my parents’ garage.” Maybe next time.

  8. When life starts to treat you well it’s best to pause and consider how suspicious that is…

    On a much lighter note, I’m sending you all the wrenching good vibes I can and hope for smooth sailing from here on out. And one more thing I’m LOVING The Autopian. You all are doing so great with this site from the content to your writers it reminds me of the heydays of a certain website from our collective past. You should be very proud of what you and the team are doing here. GREAT JOB!!

  9. Y’know, this is just a content style comment.
    I really like how clean the written and video interplay here. It made for a good smoth read and each wound up supporting the other.
    Good job on setting articles up so they are fun, not a chore, to read.
    I’m looking forward to the resolution on this XJ, carry on!

  10. I mean, the 4.0 is absolutely a reliable engine, but like anything else they aren’t unkillable… I’ve heard of a few engines that have turned #6 into piston mcnuggets, with the following result: https://youtu.be/9NoqS_yDa98?t=258 (the teardown is here, at the moment of reveal: https://youtu.be/pTE2bFyZtBI?t=838). Hopefully those sights and sounds don’t shake the foundations of your religious beliefs too much, though… wouldn’t want you to suddenly ditch the Jeeps in favor of, like, only Toyotas powered by the 22RE or something. That would be soooo boring.

    But you definitely got lucky! I can’t even remember the number of times I’ve seen guys remove belts in the hope that some accessory is the source of that sickening knocking sound, and I am pretty sure this is the first time I’ve seen it actually turn out NOT to be catastrophic engine damage. Maybe next time you sell something that’s been parked for months and months as a running driving usable vehicle, you’ll actually drive the thing around for a week or two beforehand to make sure it actually still IS running, driving, and usable 🙂

    Side note, have you ever thought about doing a 4.6L stroker build, like the latest Hagerty Redline Rebuild series? Pretty sure it uses all factory AMC I6 parts, just from different model years, to get a bit more displacement out of a modern-ish 4L block (their goal was to source all parts from RockAuto, their sponsor, so it couldn’t be anything custom).

  11. My ’97 ZJ has gone through many water pumps; most of the time, there was noticeable leakage prior to failure, but one time the only symptom was a vague, intermittent rattling sound near the front of the engine. The pump failed at highway speed, sending balls from a failed bearing through the weep hole (they make a distinct sound when they hit the underside of the vehicle) and creating impressive clouds of white smoke. As a bonus, the belt came off the pulley, shredding the nice liner on the inside of the hood. I was able to get off the road in time to prevent any further damage (or collisions, amazingly).

    1. That’s not the point. The point is fixing something so it lives on…. junking something when it just needs a $30 gasket and a $50 waterpump is still, given the condition of the rest of the vehicle.

    1. Easy solutions: she drove faster, they met somewhere he had driven away from, or she called before limping it a little farther to the gas station.
      Easiest solution: rounding error.

  12. “I had changed the oil a few years prior, but I hadn’t driven the Jeep.” What. A year, I could understand. But a FEW years?! Daaaaaaaviiiidddddd! This engine tear down is an appropriate punishment even if, as it seems, it had nothing to do with what actually went wrong. Even if you weren’t driving it, this just seems very, very wrong. Meanwhile there are some long-neglected fluids in one of my cars that I will now assume will fail as my own karmic punishment, but it won’t be the engine oil. Also, how long was the GAS sitting in that Jeep, if you hadn’t driven it anywhere? That, I know, does break down just hanging out, unless those Stabil guys are lying to me. And they would never do that.

    1. It’s basically brand new oil that, instead of sitting in a plastic bottle, sat at the bottom of a crankcase. Yes, it’s exposed to air and whatever moisture gets through that air filter and into the crankcase vent tubes, but honestly, it’s fine.

      1. DT, an oil bottle is a sealed unit. Engines breathe. The crankcase has a vent. There are exhaust valve(s) open. There are intake valve(s) open. There may be both open. The throttle plates do no seal off the intakes.

        When the atmospheric pressure changes (weather systems or just temp changes), air moves in or out of the engine and brings with it moisture. When the outside air is warmer then the engine components, that moisture condenses on the engine parts and doesn’t leave. It sits on whatever and if enough collects, it drips down into the oil. In the oil, the water changes the chemistry, including pulling out waxy solids which will no longer be around to help lubricate moving parts. The pH of the oil changes.

        Running an engine for a few minutes isn’t enough to burn off that water. You have to get the oil over the boiling point of water and keep it there until the water is gone. That means loading down the engine and making it work.
        When aircraft

        1. Stupid no edit and enter to post comment system.

          When aircraft engines go into storage, they get pickled. Oil is drained and the crankcase, intake, and cylinders get fogged with a preservative oil that creates a film over all the surfaces that will not drain into the oil sump. Then the engine is bagged up and sealed until needed again. Oil is not added until it’s time for it to go back into service. After a god engine run, it’s drained and replaced to make sure only good oil is present in the engine and as much contamination has been removed.

        2. I agree with your description of what happens to the oil, and I’ll also add that the oil with its additive packs will oxidize as well. The pH change you mention can be caused by the water mixing with various things in the crankcase and other passages and using up the buffer acids and buffer bases that are part of the oil additive pack.

          To David’s point, yeah, it’s probably “fine” for some values of “fine.” I wouldn’t choose to run an engine on aged oil for an extended period of time. My grandfather used to keep a 50 gallon drum of oil in the garage that he used for oil changes on his cars – I wouldn’t do that with what I know now. However, he never had a catastrophic engine failure, and I doubt there would be measurable differences in engine wear/damage on the jeep from its run on old oil. If you ran two engines from new, one on aged oil and one on fresh oil at each oil change, you could probably see a difference at end-of-life.

      2. I had to rebuild my Triumph’s engine because someone let the oil sit undisturbed in the pan too long and it turned to sludge.
        Granted, that could have been, like, 20 years or more for all I know, but the point remains.

  13. So it wasnt a piston skirt as we had originally suspected. Well that’s a relief, now I’m gonna hazard a guess and say that what probably actually happened that caused all this was the head cracking, like they all do on that revision of the 4.0L
    Head cracked, overpressurized the system, and destroyed the already weakened water pump making the engine make that noise. Good thing taking the head off is “easy” on those jeeps

    1. What year is this thing anyway? I know later models suffered head cracks, unless it was a TUPY head (2002+ depending on application). Thing is, older heads have different exhaust ports I think, and many mod that to put old heads in a newer 4L. Sounds like something DT would do. 😉 I am of the opinion that failed motor mounts contribute to stresses on the head, so hopefully DT checks and replaces those to finish the job right.

  14. Good to hear the fix is progressing and you are to honest to be a used car salesman. 🙂

    As far as AAA, I dumped them years ago. I was a member for over 10 years and the three, yes three, times I called (two tows and a battery replacement) I was told “We cannot help you.”

    So I cancelled and when they called to ask why I told them. They didn’t care.

    Now if I need a tow I use Blink Roadside’s on demand tow app.

  15. This is such a relief!

    I’ve actually had very similar happen on both of our 4.0 Jeeps.

    I once did a complete cooling system overhaul on my ’98 XJ, then immediately drove it 300 miles. The first time I stopped I noticed a knock so bad that I stopped and called a tow truck to take me the last 10 miles, thinking this was the end of my trusty 4.0.
    I realized a day later I’d simply failed to tighten the pulley to the water pumps properly. Tightened four bolts and she was good as new!

    Similar happened in our ’97 ZJ. It had a strange vibration at higher RPMs for a few weeks, which turned into a horrible knocking/clanking noise. I feared the worst again, but eventually figured that the water pump pulley had failed, causing the fan mounted to it to bash about.

    On a separate note, today is my 10 year anniversary with my XJ! My first car, still going strong.

    1. My old ‘91 XJ went through water pumps every couple of years. The aftermarket pumps are not always good, so the bearings never last. But once you get a “lifetime” warranty, you just keep trading in until you get frustrated and buy a quality pump…which is what I finally did. So give this buyer a quality pump!

  16. That’s good(ish) news. I just went through my first head gasket change on a Peugeot 307 and it took me about 40 hours to complete, so it’s not exactly a small job.

    The bugger still doesn’t run right though.

  17. If I know David, he’ll work day and night to fix this and get it done just in time, right before some random deadline, all the while sustaining himself only on a bowl of rust flakes and regular swings of diff fluid

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