A month ago, an attempt to speed through a deep mud pit resulted in the grenading of my Jeep’s engine. After a beautiful memorial service for my dearly departed 4.0-liter, I removed the boat anchor and took it apart. Bear witness to the carnage I found inside.
Few things in the wrenching world suck as badly as refreshing an engine and blowing it up promptly thereafter. After my air intake took a dive into the surprisingly deep pit, pistons one and six sucked in giant slugs of dirty water.
The force from the other pistons spun the crankshaft, causing the two pistons to try to compress that water. Unable to do so, the connecting rods bent, snapped, spun and crashed into the oil pan, stopping the engine cold.
The result of my muddy excursion was two gaping holes in my oil pan: one in the very front, and one at the top of the sump in the back of the engine.
Lucky for me, I found a new engine on Craigslist, so it was time to pull the blown-up one out and see the horror that lay within.
Removing The Engine
Engine removal was remarkably simple. It required the unbolting of the starter motor, airbox, battery, AC compressor, exhaust pipe, transmission shift linkage, header panel, heater core hoses, radiator, wire harness, power steering pump and six or seven bolts connecting the engine to the transmission.
I then hooked the engine to my trusty shop crane, pulled it out of the engine bay and sat it down on an engine stand so I could get a better look at the gruesome innards.
Here’s a look at the cylinder head, pistons, connecting rods and cylinder walls.
Cylinder Head
Once the engine was on the stand, I took off the cylinder head. This involved removing the 14 bolts holding the head to the block. Those bolts are gigantic and removing them after 250,000 miles was a herculean task. After destroying an adapter and straining nearly every muscle in my body, I handed the breaker bar to someone whose upper body strength doesn’t resemble that of a fifth grader. He then spun all 14 bolts without breaking a sweat.
Looking at intake and exhaust valves revealed rust in all six cylinders, indicating that at least some water got into every combustion chamber.
On the back of all the intake valves where the intake manifold bolts up, there was also was quite a bit of rust and filth:
Pistons And Connecting Rods
The force of the piston trying to compress the water was so large that it twisted and snapped two connecting rods and broke the piston skirt of cylinder six. Here’s a closer look at the fractured surface:
Here’s what the other half of the connecting rod looks like, still attached to the crankshaft:
The connecting rod rammed into the piston skirt (the piece I’m holding in the picture below) and broke it right off, sending it into the bottom of my oil pan.
Cylinder Walls
I was expecting the connecting rod to have blasted a large chunk out of my engine block, but a close look—particular at cylinders one and six— revealed a relatively smooth surface. Sure, there’s significant surface rust, but with some honing and new piston rings, this engine block is salvageable.
What’s Next?
The $145 replacement engine is already on the engine stand. I just drilled out a broken engine mount bolt, so now all I need to do is tap that hole and throw the new engine into the Jeep and that old XJ will be back on the road (or off it).
As for the blown-up engine: as it was the engine from my first car, I have an emotional connection to it, so it will live again. Perhaps it will wind up with a bigger displacement, but I haven’t yet decided.
I’ll need to hone the cylinder walls, get a new set of pistons and rods with new rings, and this old quarter-million mile torque-monster should live to off-road another day.
She’s down, but she’s not out. Not yet.