2004 MERCEDES-BENZ G350D W463

Typical onset: 100,000-150,000 mi

Symptoms: Sudden loss of power under load, Metallic knocking from lower end, Metal shavings in oil, White or blue smoke, Seized engine in worst cases

Fix: Complete engine rebuild or replacement required. Typical scenario involves dropped piston skirts, spun bearings, or crankshaft damage. Engine-out job: 40-60 hours labor for full teardown, machine work, reassembly with new pistons, rings, bearings, gaskets. Many shops recommend sourcing low-mileage used engine instead due to cost.

Estimated cost: $8,000-18,000

Typical onset: 120,000-180,000 mi

Symptoms: Overheating with no external leaks, White smoke from exhaust, Coolant loss with no visible leak, Oil milkshake under cap, Misfires and rough idle

Fix: Both head gaskets commonly fail together on V6 diesel. Heads must come off (25-35 hours), check for warpage, machine if needed, new gaskets, ARP studs recommended. Often find other issues once opened up—injector sleeves, valve stem seals.

Estimated cost: $4,500-7,500

Typical onset: 80,000-140,000 mi

Symptoms: Transmission slipping or harsh shifts, Pink milkshake in coolant reservoir, Transmission overheating warnings, Coolant in transmission pan

Fix: Internal cooler in radiator corrodes, allows coolant/ATF cross-contamination. Requires new radiator, complete transmission flush (sometimes multiple flushes), new transmission filter. If caught late, transmission rebuild needed. 6-10 hours labor for cooler/flush, add 20+ for trans rebuild.

Estimated cost: $1,200-2,500 (cooler only), $4,000-7,000 (if trans damaged)

Typical onset: 60,000-100,000 mi

Symptoms: Harsh clunk on throttle application, Vibration at idle in gear, Visible drivetrain movement, Clunking during shifts

Fix: Rubber transmission mounts deteriorate from heat and oil exposure. Requires lift access, transmission support during replacement. 2-4 hours labor, straightforward job but essential for drivetrain longevity.

Estimated cost: $400-800

Symptoms: Hard starting when cold, Loss of power under acceleration, Rough idle, Engine stalling, Check engine light with fuel pressure codes

Fix: Diesel fuel quality issues cause premature filter clogging. Water separator often full of algae/debris. Requires fuel filter replacement, water separator drain, sometimes fuel system purge if injectors affected. 1-2 hours labor, but can cascade into injector issues if ignored.

Estimated cost: $200-500

Typical onset: 90,000-140,000 mi

Symptoms: Deep knocking that increases with RPM, Low oil pressure warning, Metal debris in oil filter, Sudden catastrophic failure

Fix: Rod bearings wear prematurely, likely due to oil starvation or debris from other engine wear. Once knocking starts, you're on borrowed time. Engine-out, full lower-end rebuild minimum: crank polishing, new bearings, connecting rod inspection, 35-50 hours labor. Often discovered during diagnosis of other engine failures.

Estimated cost: $6,000-12,000