2002 MERCEDES-BENZ G-CLASS

Typical onset: 60,000-120,000 mi

Symptoms: Blue smoke on cold start that clears after warmup, Excessive oil consumption (1+ quart per 1,000 miles), Rough idle and misfires that worsen over time, Metal flakes or glitter visible in oil during changes, Sudden loss of compression leading to no-start condition

Fix: The M113 5.0L has nikasil-coated cylinder liners prone to scoring from sulfur in fuel and short trips. Once scoring starts, it's progressive engine death. Requires complete engine rebuild with re-sleeved or replaced block, all new pistons, rings, bearings. Some opt for used engine swap. 35-50 labor hours depending on approach.

Estimated cost: $8,000-15,000

Typical onset: 80,000-150,000 mi

Symptoms: Transmission fluid leak at radiator or along cooler lines, Pink fluid under vehicle (ATF mixing with coolant), Transmission slipping or delayed engagement after coolant contamination, Overheating transmission, especially when towing

Fix: The cooler lines rust through or fail at crimp points; worse, internal cooler in radiator can rupture, sending coolant into transmission (the 'pink milkshake of death'). If caught early, replace lines and external cooler (3-4 hours). If coolant contaminated ATF, add transmission flush/rebuild. Always inspect radiator internal cooler during line replacement.

Estimated cost: $600-1,200 (lines only); $3,500-5,500 (if transmission damaged)

Typical onset: 70,000-130,000 mi

Symptoms: Clunking or thudding when shifting from Park to Drive/Reverse, Excessive vibration at idle in gear, Visible transmission sag or misalignment when inspected on lift, Harsh engagement into gear

Fix: The 722.6 five-speed transmission sits on rubber mounts that crack and collapse from age, heat, and the G-Class's truck-duty cycle. Requires replacing front and rear transmission mounts. Access is tight but straightforward with proper support. 2-3 hours labor.

Estimated cost: $400-700

Typical onset: 90,000-140,000 mi

Symptoms: White smoke from exhaust (coolant burning), Overheating with no external leaks, Coolant loss with no visible puddles, Oil cap/dipstick shows milky emulsion, Compression test shows adjacent cylinders low

Fix: M113 head gaskets fail from age or overheating events (often cooler-line related). Job requires removing both heads, resurfacing if warped, new gaskets and bolts. If caught before warping, 18-22 hours. If heads need machining or engine has scored cylinders, you're into rebuild territory.

Estimated cost: $3,500-5,500

Symptoms: Hesitation or stumbling under acceleration, Hard starting after sitting overnight, Loss of power at highway speeds, Intermittent stalling, especially when fuel tank below half

Fix: In-tank fuel filter clogs from sediment, especially in trucks that sat or used questionable fuel. Mercedes spec says lifetime filter, but real world is 60-80k miles in dusty or humid climates. Requires dropping tank or using access panel if equipped. 2-3 hours labor.

Estimated cost: $300-550

Typical onset: 80,000-150,000 mi

Symptoms: Gear oil drips or puddles under front axle or transfer case, Visible oil coating on differential housing, Whining noise from front end if oil level drops significantly, Burning oil smell after highway driving (oil hitting hot exhaust)

Fix: The G-Class's full-time 4WD system has multiple shaft seals that weep with age. Front pinion seal, axle seals, and transfer case output seals are common culprits. Not urgent if caught early and fluid topped off, but neglect kills bearings. Seal replacement typically 2-4 hours depending on location.

Estimated cost: $350-800