Last night I found myself in a dumb situation only I could have gotten myself into. I had sold a beautiful 1991 Jeep Cherokee to a nice Chicagoan named Tracy, who only managed 20 minutes of her 4.5-hour drive home before her new vehicle blew up. I took the Jeep back, promising Tracy I’d bring the venerable 4.0-liter engine back to life. She took my word for it. She believed in me. She ditched all of her other vehicles, and was now depending on me, giving me a deadline of June 14 or else she’d be carless. Last night, I realized that today I’d be flying to California to drive the 2023 Ford Bronco Raptor, meaning I had to fix the Jeep right now or Tracy was screwed. I wasn’t going to let that happen without a fight.
I write to you utterly fatigued from a cramped airplane on its way to Palm Springs, where I plan to off-road the crap out of a 2023 Ford Bronco Raptor. I’ve got a half-inch bloody gash in my left pinky, oil underneath my fingernails, and — though the woman sitting next to me hasn’t mentioned it — most likely a light smell of ethylene-gycol-based engine coolant emanating from my pores. I know I look like shit, my body definitely feels like shit, and yet somehow I’m on top of the world right now — not because of the Bronco Raptor, though that’s likely to be epic, but because last night I broke out every weapon in my toolbox and finally slayed the mechanical menace that is my beautiful 1991 Jeep Cherokee five-speed.
The overheating episode shortly into Tracy’s drive home had warped and cracked the Jeep’s cylinder head, killing compression in four of six cylinders. The vehicle ran on the remaining two, but it released a sound so traumatzing that I was forced to discard it from memory.
I zipped a cylinder head off the parts engine sitting in my garage, sent that into a machine-shop to be checked and shaved flat, and bolted that lid onto the exposed iron heart nestled between the shock towers of a truly gorgeous but thoroughly flawed AMC-designed box-on-wheels. Unfortunately, despite the engine now running well with its new head, the motor continued overheating and appeared to be gaining oil. I feared the engine had cooked itself during Tracy’s short drive and the block was now cracked.
There’s a reason why I feared the worst. I’d seen these exact symptoms before: A slight increase in oil volume on the dipstick accompanied by chronic overheating. And on all occasions, I’d sent an oil sample to Blackstone Labs, who told me that indeed, there was coolant in the oil. Check out these three Blackstone reports from a 1992 Jeep Cherokee, a 1995 Jeep Cherokee, and a 1996 Jeep Cherokee:
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All of these Jeep Cherokees ended up requiring new cylinder heads. But since I’d just replaced the 1991 XJ’s head, it wasn’t a stretch to take the overheating+gaining oil symptoms as a sign that the block had been compromised.
I’d pressurized the cooling system with a hand pump, and found that there was a slight leak (the pressure shown on the gauge dropped slowly). But I noticed no obvious drips, so perhaps it was internal? A cracked block would explain this pressure drop, and it would explain the overheating and the increase in oil level. But why was the engine making good compression? Couldn’t a cracked block compromise this? Why wasn’t there any steam coming out of my exhaust? Why was this increase in oil not accompanied by the signature milky consistency of a water/oil mixture? Why didn’t my block testing die detect any combustion gases in the cooling system?
I was still not convinced I had a block issue.
I thought about this Jeep all day yesterday when I really should have been writing/editing/running this business. I asked myself two questions. The first was: Am I 100 percent sure that the engine is gaining oil?
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After installing the new head, I’d run the engine and noticed the oil level was elevated well above what six quarts tends to read on a Jeep 4.0 dipstick. But then again, I had poured some Marvel Mystery Oil into those cylinders, and some might have gotten into the crankcase. To get rid of that factor, I then conducted an oil change, but since I feared coolant was getting into my oil, I didn’t want to waste my good stuff, so I just grabbed some spare jugs I had sitting around. I used an old gallon jug of Rotella 10W-30 to measure out six quarts of cheap lubricant, but had I been precise? Was I truly 100 percent certain that this engine was gaining oil?
On top of that, since the oil didn’t look milky, could that have been fuel in the oil? I poured some fuel injector cleaner into my gas tank, and revved the living crap out of the engine. Accelerating that little Jeep made me realize just how magnificent the machine is. There’s just so much power and torque in just a 3,350 pound package; when this engine debuted in 1987, it must have blown people’s minds.
The second question I asked myself yesterday when I was daydreaming during work hours was: Why is the Jeep only overheating under certain conditions? It seemed that high-speed highway driving and idling were the worst-case situations. The former involves lots of engine heat rejection, the latter involves little coolant or airflow.
As I’d previously had issues with coolant temperature sending units on both Jeep Cherokees and Grand Cherokees, I dropped the $8 on a new one to make sure i was at least getting the correct readings on my gauge. Deep down, I knew the sending unit wasn’t the problem, because the temperature gauge was reading right in the middle under medium-speed, low-load driving conditions — especially when the revs were above 2,000 RPM. If the needle reads appropriately under not-particularly-taxing thermal conditions, then the sensor is probably doing its job, and the issue is actually with the system’s thermal capacity.
My soccer game on Monday night had given me a lot of information. I’d driven roughly 40 mph on back roads the whole way home, and the needle stayed firmly in the middle, only elevating when I stopped at my house and let the motor idle a bit. “This cooling system’s ability to reject heat seems to be compromised,” I thought. Sure, a cracked block would prevent the system from reaching its 13 PSI pressure, and could cause the vehicle to overheat, but the pressure leak wasn’t really that bad; I was able to pressurize the system with that hand pump, and the needle remained at 13 psi for quite a while before dipping down to 12. I’d driven a Willys Jeep across the country with a cooling system pressure of fairly close to ZERO PSI (there was a little leak in the radiator), but as long as I kept the rad full, the engine never overheated. I’d had pinhole leaks in radiators before, and those engines still stayed cool as long as they had water (“water,” by the way, is what people in the auto industry call engine coolant, by the way) in them.
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More importantly, as I sat there at my house at 11 PM after my soccer game on Monday, with the AMC straight-six idling and me staring at the gauges like a weirdo, I slid my heater lever to the right and immediately felt those glorious joules that were once contained in gasoline blow through my vents. The temperature needle dropped to the middle. Hmm.
I thought about all of this yesterday after work when I realized that I’d be returning from my Bronco Raptor trip the last weekend before Tracy’s deadline. There would be no time to continue diagnosing the Jeep when I got back. Tracy needed a Jeep by the 14th or she’d be walking, and I couldn’t drive to Chicago during the week due to work. I had to deliver this Jeep to Chicago as soon as my flight landed from California, meaning I understood last night that I had to fix the Jeep RIGHT NOW. That was not the greatest realization, I will admit.
I ordered a radiator at about 6 PM, picked the plastic-and-aluminum heat exchanger up from the store, and began installing it. In my head, it was plausible that the oil increase on my dipstick had been either a leaky injector or just me being imprecise in my measurement, because in the past couple of days (including my drive to and from my soccer game) the Jeep appeared to have gained no oil whatsoever. As for the overheating, I reasoned that if all it took to keep the temps down was a little bit of assistance from my heater core, then maybe a more effective radiator would do the same. So I was praying that my only issue was radiator-related.
A reader named Jeremy had messaged me on Instagram to see if I wanted to meet up, as he was in town from Toronto. We’d agreed to go to a bar, but I switched plans on him. He generously came to my EPA Superfund Site and assisted with my radiator replacement, which would end up costing me a reasonable $135 in parts, all told. The job took about two hours; I removed the entire fiberglass header panel (which contains the lights and grille), took off the upper radiator support beam, undid the coolant hoses from the radiator, removed the electric fan, unfastened the mechanical fan shroud, and plucked the old radiator right out. It appeared to be in fine shape, but it also looked to be the original unit (based on the Chrysler stickers present). That’s an old heat exchanger.
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[Editor’s Note: I’ve seen David’s place in conditions of disarray that make a recently-bombed recycling plant look like Martha Stewart’s lakehouse. If David is saying he doesn’t want someone to see the condition of his house, I’m not sure I can imagine what that could mean. Is it crawling with filth-snakes? Knee-deep in cheese, mold, and mud? Did he just start shitting onto newspapers on the floor? Who the hell knows. – JT]
I had to drill into two of the brackets on the new radiator to make it fit, but — thanks to Jeremy’s help lining the bottom mounting posts up with the holes in the lower radiator support in the Jeep’s unibody — the installation job was largely drama-free. At around midnight, we had the cooling system back together and were pouring gallons of antifreeze into the system.
Then we hit the highway, which was empty at one in the morning. I punched the accelerator pedal until the Jeep was driving 75 mph, generating lots of heat from that 4.0. Then I waited for that needle to rise from its center position, slowly but surely. But it refused. It sat there, unwavering. I hammered the gas pedal a bit harder, but the needle remained pointed at 210. I then pulled off the highway and idled the Jeep; this is typically a taxing thermal condition because all the heat that the engine creates in order to propel the car at high speeds still needs to be rejected (it’s not an instantaneous process), except now you’re at idle with low water flow and low airflow.
The Jeep didn’t give a damn. It continued to run at its normal operating temperature.It wasn’t the relatively cold ambient temperature outside giving me false hope, either; the prior cool night, after my soccer game ended around 11 PM, I noticed overheating at idle. But now, no matter how long the Jeep sat stationary, the new radiator had no problem transferring that engine heat to the incoming air. My overheating issue was gone. It was a clogged radiator.
In retrospect, the coolant coming out of the old rad was pretty damn brown, so maybe I should have known. But I’d been burned so many times by overheating Jeep Cherokees gaining oil due to cracked engines that it was impossible for my mind not to go there.
After four years, the XJ from hell has been rescued. Now it’s time to get rid of it as quickly as I can before it tries to ruin my life further. I wouldn’t be surprised if it performed flawlessly for Tracy for years to come. I truly hope it does.
In retrospect, the coolant coming out of the old rad was pretty damn brown, so maybe I should have known. But I’d been burned so many times by overheating Jeep Cherokees gaining oil due to cracked engines that it was impossible for my mind not to go there.
After four years, the XJ from hell has been rescued. Now it’s time to get rid of it as quickly as I can before it tries to ruin my life further. I wouldn’t be surprised if it performed flawlessly for Tracy for years to come. I truly hope it does.
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Well done! I know I am not alone in having been waiting for this exciting update! Came down to the wire, but well done man! Congrats on finally getting it done. Make sure to give another update, hopefully a much less exciting one when you get it delivered. I truly hope it is like 3 lines long, drove to Chicago, nearly died due to gas prices, dropped off the Jeep from hell to the nice lady, drove/got a ride home, gas prices again caused tears. The end.
Well done, sir. Nothing like walking into the house covered with car dirt and saying “I win.”
Enjoy driving the new Bronco Raptor. I am sure nothing could go wrong with the engine of a brand new Bronco!
Happy to hear you got there in the end, congrats!
Maybe David doesn’t want people to see his human skin lampshades ?
By the way: Thanks to everyone who gave me suggestions! Especially rootwyrm!
Congratulations on the repair. I had an old truck that had the same symptoms as your Jeep. Thankfully I didn’t have to troubleshoot it because the radiator blew a side partially off when I was revving it in my driveway! When it blew apart a ton of black crap spilled out onto the ground.
I watch a lot of YouTube mechanics videos and one guy said a way to diagnose a clogged radiator was to use a temp gun to find cold spots on the radiator. Good tip to keep under your hat!
My pleasure! I’m just glad I could put some of my rusty knowledge to good use. 🙂
FWIW, I was halfway leaning toward radiator but … yeah. You know why I didn’t want to tell you to just replace the radiator, besides cost. That job sucks.
Root cause from a distance, at this point, I think I have a pretty good idea of what exactly happened here. One, you had a silent head failure going on for several thousand miles. But it wasn’t bad enough to warrant pulling it by any stretch. No milkshake, no problem(TM). When the water pump went, the system got hot, which starts dislodging all the Sluj(R) that built up in the system. Add air ingestion into the mix, and you can just imagine the frothy delight going on in your radiator. (Please don’t if you plan to eat today.)
So all that crap got pumped into the radiator, with nowhere to go because the water pump wasn’t working at all. Which consequently clogs up the channels. But these bastard radiators are downflow. Something you probably did not learn in your time at Chrysler: downflow radiators are REALLY fucking good at hiding even significant blockages. You’ll hook up the garden hose going full blast, and get as much out the bottom as you seem to be putting in the top. Even when literally half the channels are completely plugged. (Remember, we didn’t have fancy $40 IR thermometers back then. We were lucky if we had a meat thermometer. :P)
Because the radiator doesn’t have much margin, and has offset fans? Yeah. You know what happens there. It’s why people are completely wrong when they insist 3-row downflow units are ‘better.’ It’s always been the margin versus Coolange(TM) Sluj(R), and the Sluj(R) always wins. Because it’s a downflow. And when you have an entire side getting zero coolant with unequal fans, uh-huh. Which is exactly why you check fans first – bad fan acts like a plugged radiator, but is far less painful to fix.
Glad it got rectified! Onwards and upwards!
Actually considering the clusterfuck this ended up being I introduce the verb rectumfied to our lexicon.
This is the ending we all waited for!!! Congrats!
Filth snakes, slithering in mold-cheese and DT shitting on newspapers strewn on the floor
Although the lady next to me didn’t say anything, I’m sure I smell of polyethylene glycol
wrenching at the expense of my social life, relationships, etc
Glad it is fixed.
The downside is I have the image of Torch’s description of David’s house in my mind. I guess that is revenge for the Torch with Puppies image. Well played sir, well played.
I’m seeing a kind of cross between a Hoarders episode and Roadkill’s parts supply; all shoved into a suburban Detroit 2br ranch house.
Outstanding work DT!
Now get rid of that POS as fast as you can.
Congratulations! There is no better feeling than taking that victory lap and realizing that it really is fixed! The satisfaction of bringing an old car back to life and sending it on its way, confident that it will serve its new owner for years to come is awesome as well!! Good stuff! Now, give that Raptor a good thrashing for the rest of us!!
VICTORY!
Its always a sweet sweet thing when you get there. Makes all the headaches and stress go away. Most of the time, at least.
Congrats, man. Now maybe clean your house?
I probably spent $4000 in total on it. And 6.02×10^23 hours of my life. I sold it for $7 large.
Avogadro’s number!
Never mind you have not been alive that long…
🙂
Neither has the universe…
Since Avogadro’s number of hours would be almost 5 trillion times longer than the age of the universe (which is 13.8 billion years)
This site needs GIFs to acknowledge this achievement.
https://c.tenor.com/dvug8uL9FuIAAAAC/applause-the-rock.gif
Told ya it was something simple! I didn’t mention radiator because believe it or not, you really are supposed to do all those things before condemning the radiator unless you have OBVIOUS radiator failure such as a leak or obvious bulge. Discoloration isn’t enough to be obvious radiator failure. The amount of Coolange(TM) Sluj(R) in 4.0’s means green + clear = toddler diarrhea brown.
You just did the replacement job. You know exactly why we avoided condemning a radiator prematurely. Especially since you had to try the petcock first to try and avoid hose replacement.
The absolute worst trap any mechanic can fall into is second guessing their work infinitely. Absolutely if a mechanical repair doesn’t fix the problem, you double-check your work. But you have to stop questioning your repair if it tests okay. The issue wasn’t the work you did, so you have to go back to diagnosis with confidence and understand that it’s a complicated machine and you’re only human. Multiple problems not only can be, but commonly are present.
In other words, “I didn’t repair the vehicle incorrectly, there is another problem present which I could not see without repairing the first problem.” You could not have possibly seen or diagnosed a partially plugged (it was a partial, not a full) radiator without first replacing the cylinder head, water pump, and ruling out every other potential cause such as faulty sensors and broken fans.
At this point, the Jeep has been gone through with a fine-toothed comb. The only real failure I’d expect for the next 50-100k miles with proper maintenance would be the fan clutch if it wasn’t replaced before, or possibly the aux fan. That’s it. Okay fine, maybe a transmission solenoid pack.
So the old radiator wasn’t radiating?
If we’re gonna adhere to the problem-solving protocols, you can’t really call it the “red X” until you cut the old one apart and actually find the plugging.
I’m hearing: perfectly good old radiator, just add Evap-o-rust.
It was radiating pain and sadness…
It was radiating, but it wasn’t convecting like it should
First off, I want to say congrats! Also, did you remember to take off the headband spotlight before you got to TSA this morning? You are an absolute maniac 🙂
A semi-serious question though:
After its all is said and done, including the drive to Chi town (which, btw, is a maniac thing to do right after a flight from Cali. Forget trench foot, you’re gonna give yourself hemorrhoids!), how much money did you lose in total on the car?
Rule number one of wrenching on old cars you love: Never add up the totals.
Fortunately it would appear any love DT had for this Xj has long since been beaten out of him. Numbers please!
“how much money did you lose in total on the car?”
Only his accountant & (maybe his therapist) are privy to those numbers.
Yay, congrats! Your euphoria definitely comes through!
Also, I believe you have just delightfully illustrated the traditional plot arc of a superb romantic comedy:
–Meet-cute (boy meets XJ)
–Appealing leads with quirks and idiosyncracies
–Vexing obstacles to surmount
–A helpful and charismatic sidekick (from Toronto)
–Happy ending (not necessarily together, which adds evocative depth)
Extra credit: a Chicago thematic element
I can’t wait:
Autopian: The movie
You’d have to watch it at the drive-in, obviously.
…which would be an oil-stained sheet hung off the back of David’s garage, showing the film to people sitting in a his collection of old, rusty, floorless Jeeps. At least for the premiere.
You joke, but I remember he actually did this back in 2020 as a socially distanced social…
A two-door manual XJ is definitely the manic pixie dream girl of the Jeep world.
I have seen Martha Stewart’s lakehouse. David would not be allowed onto the property. I
I don’t know about that. After splitting a blunt with Snoop I bet Martha chills a good bit.
Martha is very uptight. She would have her gardener take care of the problem
#winning
I had a similar issue with my ’87 XJ, it would overheat under specific conditions, but not all the time and had no other indicators of internal engine issues(water in oil, combustion gas pressurizing the coolant system, etc). I eventually changed the radiator for the same reason that you did – running the heater helped quite a bit – and it never had a cooling system problem again. I sold it at 350K miles and I saw it cruising around town for at least a couple years after I sold it. I kinda wish I’d have kept it, it was a rare two-door model and in pretty good shape, but nearly every piece of plastic in the interior was bleached out and/or otherwise ruined and I could never find a two-door in a junkyard to rob parts from.
I have used the “heater fixes it” radiator diagnostic test twice on Subaru’s. I own one of those pistol grip IR thermometer gizmo’s, but there’s just too much crap around a radiator any more. Can’t get a hand on it anymore either.
Wrenching late into the night, peeing in the backyard, and hopefully having a cold one nearby sound like good times. I remember when going to the bar sounded like more fun than this but probably not anymore. Getting older is a strange journey.
Congratulations on fixing it! It’s a wonderful feeling, isn’t it?
David, I knew you could do it! I think you, like me, are powered by spite, stubbornness and sheer force of will.
I think one of the commentors mentioned the radiator yesterday, but it always seems to be the basic stuff that bites a guy. Sometimes you just need to step back and assess.
Yeah I used to be that guy. I would go out of my way to find the brick wall, I would stubbornly thrust my Lance at the windmill. Nowadays not so much. The wall and windmill always win and it eats at your soul.
Hooray! I love reading stuff like this. The trouble, the thought process, the trials and errors, and ultimately the big pay off of victory!
Plus, instead of just having a beer at a bar with David Tracy, he got to do David Tracy things with David Tracy at Chateau David Tracy! Wins all around!
Yeah sounds fun, and I mean that!
I hope there was beer involved at some point, though…
Great job, now enjoy thrashing the Bronco Raptor!