I should have been in Chicago on Sunday, but instead I sit utterly defeated here at my house in Troy, Michigan. I’m covered in oil and coolant; lack of sleep has sprouted saggy bags under my eyes, which now stare blankly into this screen as my fingers bang out the words you’re reading with little input from my now barely-functioning brain. I have been defeated. All day Saturday and Sunday — the entirety of my weekend — involved me, a former Jeep cooling system engineer, being absolutely decimated by an overheating Jeep Cherokee XJ. I’m thoroughly annoyed, I’m thoroughly tired, and the buyer of this Jeep Cherokee may be thoroughly screwed.
I cannot even think back to the last weekend where I wasn’t fixing something. Truly, I think at least 90 percent of my non-travel weekends between age 24 and 31 (well, in two months) have involved wrenching on a shitbox. That’s seven years of my youth occupied by the ol’ wrench.
You’d think that the result of a youth spent with machines and not people my age would be an ability to fix damn near anything. And every now and then, like when I — even encumbered by a case of trenchfoot — revived a 1958 Willys FC that had sat for decades, I do begin to wonder if I’m hot shit with a toolset. But more often than not, any budding cockiness is swiftly crushed by the wrenching gods before it ever sprouts; that’s what happened this weekend.
It was a simple cylinder head job; I’d conducted the job four times prior, so I wasn’t anticipating any trouble from the beautiful 1991 Jeep Cherokee five-speed that I’d sold to the family that had ordered the Jeep from the factory way back in 1990. Sadly, 20 minutes after the buyer left with the title (no money has exchanged hands, she was going to wire it to me) to head back to Chicago, she told me the Jeep had overheated.
It was a tough call to get, because the amount of work I’d done to this XJ since going through hell to buy it back in 2018 — just to get it into selling shape — is shocking; The fact that the Jeep still isn’t finished made my heart sink. I was inching towards freedom; soon I’d no longer be weighed down physically and emotionally by American iron, but the AMC gods thought differently, and shoved the 9/16 swivel-head ratchet wrench right back into my hand.
You’ll understand why I was so bummed when you look at this list of repairs I made prior to the sale in April:
- Replaced front left fender (which I had professionally painted)
- Replaced front left fender flare (which I had professionally painted)
- Replaced front left fender liner
- Replaced front bumper (which I had professionally painted)
- Replaced rear bumper (which I had professionally painted)
- Replaced front axle
- Replaced front axle u-joints
- Replaced front ball joints
- Replaced steering tie rod ends
- Replaced steering drag link
- Replaced steering intermediate shaft
- Replaced steering box
- Replaced control arm bushings on front axle
- Replaced front axle seals
- Replaced front axle disconnect motor
- Replaced front wheel bearings
- Replaced front brake pads
- Replaced front left wheel
- Replaced all four tires
- Replaced all four shocks
- Replaced rear leaf springs
- Replaced driver’s seat
- Replaced driver’s door check-strap
- Fixed rear hatch interior trim
- Replaced front windshield wiper motor/transmission
- Replaced engine computer
- Replaced radio
Holy crap that’s a lot of work, and for what? So I could store the vehicle (which I considered the most perfect Jeep ever made when I bought it, with plans to keep it forever) for four years and only drive it a total of maybe 50 miles.
This XJ Cherokee ownership experience has been a failure in every way. I haven’t driven the Jeep, I’ve spent years fixing it, and once I finally had all of those repairs done and I thought I could finally part ways with this mechanical menace that had haunted me for far too long, the XJ decided to come right back and kick me one last time. And this time I’d be on the receiving end of the most painful blow yet.
After the Jeep overheated 20 minutes into the buyer’s (that’s Tracy) drive, she drove back in the car she’d piloted to Michigan, and I’d agreed to mend the engine. I heard a fairly loud knocking sound coming from the bottom of the motor, but once I learned that this was just the water pump banging around a bad bearing, I felt at ease. I could replace a water pump. Unfortunately, the Jeep wasn’t running properly; a compression check confirmed that the cylinder head had failed, and a machine shop later confirmed that it had cracked.
That brought me to this past weekend.
I had a freshly-shaved cylinder head ready to go, along with a new cylinder head gasket, new head bolts, a new water pump, a new thermostat, and a bunch of other replacement parts that typically accompany a head-job. After lapping the valves and swapping the valve stem seals for good measure, I threw the new head gasket onto the cleaned-off deck:
Then I maneuvered the absurdly heavy cylinder head onto the engine. I’ll admit that I didn’t get it aligned perfectly, and had to slide both the head on top of the gasket as well as the gasket on top of the deck. But the surfaces were smooth, and everything slid easily until I could get all my head bolts tightened up.
There’s a specific sequence one has to follow when tightening cylinder head bolts. It’s all about making sure that the head squishes down evenly on that gasket. I followed protocol, and then fastened up a new water pump and thermostat, hooked up the intake and exhaust manifolds, bolted up the power steering pump, slid the belt back on, connected the ignition system, filled the cooling system, and did a whole bunch more to get the Jeep finally ready to fire up.
After an initial ground strap issue, the Jeep followed the request from that ignition switch in the gray Saginaw Steering column and sprung to life. The motor sounded good. So that’s it, right? I’ve fixed the failed cylinder head, now the Jeep is ready to go to a new owner.
As I said before, this Jeep is a menace. You see that list of nearly 30 parts I’ve already had to replace? This XJ is going to make sure the count hits 50. It is on a mission to take the remaining scraps of my youth and turn it into busted knuckles and oily bedsheets.
Despite my new water pump, thermostat, and radiator cap, the Jeep keeps overheating, especially at a long standing idle. Steady-state conditions where I keep speeds below 50 mph, it’ll run cool seemingly indefinitely, but crank the speeds up to 75 or come to an idle, and the need whips clockwise towards the dreaded red.
After buying a special funnel to ensure that the system was completely deaerated, I broke out a bunch of tools to determine what’s going on. The first was a radiator pressure tester. I screwed it onto my radiator, pumped the cooling system up to my radiator cap’s 13 PSI rating, and waited.
The needle fell, indicating that I have a leak somewhere. Sadly, that leak does not appear to be external, as even a close inspection of the radiator, water pump housing, and thermostat housing shows no dripping ethylene-glycol mixture.
The second tool I used was a “block tester” (shown on the left), which basically involves pouring a blue detection fluid into a cylinder, shoving that cylinder into the radiator, and sucking air from the cooling system through the blue fluid. If there are combustion gases in the coolant, they will turn the blue detection fluid yellow, meaning there’s a head or head gasket issue. My test fluid remained blue.
I also broke out my compression gauge, finding all cylinders to read between 100 psi and 120 psi — these are below the 120 to 150 spec, but maybe the gauge isn’t reading right. What’s more important with compression tests is consistency across all cylinders, and my engine has that, and does not burn any oil.
That brings me to the real problem: The motor does gain oil.
Yes, my oil reading on my dipstick is increasing. Between that and my lack of cooling system pressure, I suspect an internal problem. Do I have a cracked block? Did I somehow screw up my head installation? Maybe my bolts bottomed out or my gasket scuffed during installation? I don’t know the answer to these questions.
I may send an oil sample out to Blackstone Labs to have them confirm that it is indeed coolant in my oil and that I am indeed utterly screwed. Until them, I’m going to make a few other adjustments, maybe add some fuel injector cleaner to my fuel (lest I have an injector that’s leaking gas into my oil), tighten some hose clamps, and possibly thread a mechanical temperature gauge into my cylinder head for a more reliable reading.
This Jeep has been a nightmare since I bought it off that used-car lot in Indianapolis in 2018. I was lured by its beauty, its manual transmission, its awesome vent windows — but as they say, it’s what’s inside that counts, and this Jeep is rotten to the radiator core. Just yesterday while trying to suss out this cooling issue, I learned of a failed upper control arm weld, so I’ll be replacing that, too.
Have mercy Jeep gods. Let this just be a bad injector and a loose hose clamp. I don’t want to lift that heavy cylinder head off that engine. I really, really don’t. More importantly, I want to deliver Tracy a reliable Jeep; she’s in a pickle right now, as she was expecting this machine to work, and has no other car to get around. So the pressure is on.
Save ya a sample to Blackstone- get a business card and place a single drop of oil on the back in the center of the card. Put the card drop-side up on a cup or shot glass overnight, then inspect the back of the card the next day. Coolant will make a halo around the oil drop if it’s present.
A couple years ago my 1985 Jeep CJ had a vibration/rattle under the hood that would change with engine speed. I looked for any loose part. I even put strips of rubber under the headlight trim rings in hopes it was something simple. The rattle persisted. I was sure it was the water pump, so I replaced that. Nothing changed. Then I was sure it was the power steering pump which was the original pump. I lined up a replacement. Then, for some reason, I thought maybe the rattle wasn’t coming from under the hood. I slid under the Jeep and smacked on the exhaust system hoping to hear the familiar rattle. I got to the catalytic converter, smacked it, and bang, there was the rattle. After a decade, one of the ceramic inserts had gotten out of position and was literally rattling around inside the metal shell. I pulled it out, put in a straight pipe, and problem solved.
It is funny reading through the list of stuff that you have done to that Jeep as I have done all of that and more on my ’94 F150 which, in contrast, I consider a great truck and never want to part with. I have been tempted over the years to get a different truck, but I stick with “the devil I know”. Every part I replace is one less thing I have to worry about, and I have done a lot of this work preemptively. It also helps that it is not my daily, and I do not have a customer waiting for it. It is all about perspective, I guess. I winced when you mentioned having to possibly redo the head gasket. My inline 6 Ford has a big iron head not unlike what you are dealing with, and it was a BEAR. Good luck getting it finally sorted. David Tracy will not be conquered by any car!
“Then I maneuvered the absurdly heavy cylinder head onto the engine. I’ll admit that I didn’t get it aligned perfectly, and had to slide both the head on top of the gasket as well as the gasket on top of the deck. But the surfaces were smooth, and everything slid easily until I could get all my head bolts tightened up.”
Please don’t ever do this. If the block/head combo you’re working with doesn’t feature alignment dowels, then go to the hardware store and buy four long bolts with the same thread pitch as the head bolts. Cut the heads off, notch the ends so a flathead screwdriver fits and then screw them into the block to act as guides when positioning the head.
Another practice I recommend is to retorque the head bolts after letting them set overnight. Following the pattern in the service manual, crack each one loose and torque it back to the exact same spec. If you mark the heads with a paint pen beforehand, you’ll notice that the bolt head position actually advances a little even though the same torque is being applied.
Additional thought – have you replaced the hoses? I’m wondering if one might be collapsing enough to restrict coolant flow at higher revs.
Farty’s rules for interacting with David Tracy:
1. DO – Read every article he writes. They may inspire you, make you laugh, make you question his (and sometimes your) sanity, and are generally entertaining and informative.
2. DO NOT – Ever buy a car from him, no matter how reliable he says it is or excited he is about owning it.
3. DO NOT – Rent him any home if you are not ok with the property around said home being a parking lot / mud bog.
4. DO NOT – Take his advice about about what a reliable vehicle is (see rule #2). He does not understand what that word means.
Came back to add that we are eager to learn the results of the oil analysis. My suggestion is, until you have those results, get a Coney Island and a Faygo to be good to yourself. If the oil analysis shows contamination, you can quit chasing gauges, sensing units, etc.