1994 MERCEDES-BENZ G-CLASS

Typical onset: 120,000-180,000 mi

Symptoms: Excessive oil consumption (quart every 500-800 miles), Blue smoke on startup or acceleration, Loss of compression and power, Failed emissions tests

Fix: The M117 aluminum-nikasil cylinders wear unevenly, especially if low-quality oil was used or maintenance skipped. Full engine rebuild required: bore honing or replating, new pistons, rings, bearings. Expect 35-45 labor hours for complete teardown and rebuild. Many owners opt for short block replacement instead.

Estimated cost: $6,500-12,000

Typical onset: 80,000-140,000 mi

Symptoms: Transmission fluid leaking from front of vehicle, Trans overheating warning or slipping, Metal debris in transmission pan, Sudden loss of all gears

Fix: The external trans cooler lines corrode and the cooler itself clogs or ruptures, especially in rust-belt vehicles. Contaminates transmission fluid with coolant or allows complete fluid loss. Replace cooler, all lines, flush transmission, and replace filter. If caught late, transmission rebuild needed. 4-6 hours labor for cooler/lines only.

Estimated cost: $800-1,500 (cooler/lines), $3,500-6,000 (if trans damaged)

Typical onset: 100,000-160,000 mi

Symptoms: Coolant loss with no external leaks, White smoke from exhaust, Milky oil on dipstick or cap, Overheating under load, Rough idle or misfires

Fix: The M117 head gaskets fail from age and thermal cycling, often between cylinders or into coolant passages. Both heads should be removed, surfaced, pressure tested. Replace all gaskets, timing chain components while in there. 18-24 labor hours for both sides. Often combined with other engine work since it's apart.

Estimated cost: $3,200-5,500

Typical onset: 60,000-120,000 mi

Symptoms: Clunk when shifting into gear, Vibration at idle in gear, Excessive driveline movement, Transmission hitting crossmember or tunnel

Fix: The rubber transmission mount deteriorates from heat and age, allowing excessive movement. On a truck this heavy with an old 4-speed auto, the mount takes serious abuse. Replace mount and inspect driveshaft flex discs simultaneously. 2-3 hours labor, straightforward job.

Estimated cost: $350-650

Symptoms: Hard starting after sitting, Stumbling or hesitation under acceleration, Stalling at idle, Loss of power on hills

Fix: The Bosch K-Jetronic mechanical fuel injection system is sensitive to varnish and debris. Old fuel, sitting for months, or infrequent filter changes cause clogging. Replace fuel filter (should be every 15k but often neglected), clean fuel distributor, check accumulator. If system sat with bad fuel, injectors need ultrasonic cleaning. 1.5-3 hours labor depending on scope.

Estimated cost: $200-600

Typical onset: 140,000-200,000 mi

Symptoms: Knocking noise on cold start that lessens when warm, Metallic ticking under load, Low oil pressure at idle, Metal shavings in oil filter

Fix: Extended oil change intervals or running low on oil causes bearing wear on the M117. Requires full engine teardown, crankshaft inspection and possible machining, all new bearings. Often discovered during compression diagnostics. 30-40 hours labor for complete lower-end rebuild. If crank is damaged, core replacement needed.

Estimated cost: $5,000-9,000