1997 MERCEDES-BENZ G-CLASS

Typical onset: 80,000-140,000 mi

Symptoms: white smoke from exhaust on cold start, coolant loss with no visible leaks, milky oil on dipstick or oil cap, rough idle and misfires, overheating under load

Fix: Both head gaskets typically fail together or in sequence. Job requires pulling both heads, resurfacing, new bolts, timing chain verification. 18-24 labor hours at a competent shop. While you're in there, do valve stem seals and water pump or you'll be back in six months.

Estimated cost: $4,500-7,500

Symptoms: random misfires that move between cylinders, intermittent check engine light, rough running when engine is hot, crank position sensor faults, sticky residue on harness near engine heat

Fix: Mercedes used soy-based wiring insulation in this era that literally disintegrates. Engine harness replacement is 8-12 hours depending on how much you chase into the firewall. Aftermarket harnesses exist but OE quality varies wildly by supplier.

Estimated cost: $1,200-2,400

Typical onset: 90,000-150,000 mi

Symptoms: transmission fluid leaking at radiator connection, pink fluid pooling under front of vehicle, transmission slipping or delayed engagement, burnt transmission fluid smell, coolant mixing with ATF in severe cases

Fix: The steel lines rust through where they connect to the radiator-mounted cooler. If coolant mixes into the trans, you're looking at a full transmission rebuild (add $3,500-5,000). Preventive replacement of lines and external cooler is 3-4 hours. Do NOT ignore seepage.

Estimated cost: $600-1,200

Typical onset: 120,000-180,000 mi

Symptoms: deep knocking sound from bottom of engine, worse when cold, metal shavings in oil, low oil pressure at idle when hot, sudden catastrophic failure with no warning in worst cases

Fix: Rod bearings wear on the M119 if oil changes were stretched or wrong viscosity used. Requires full engine-out teardown, crank inspection and possible machining, all bearings, new oil pump. 25-35 hours. Many shops recommend short block swap at this point since you're that deep already.

Estimated cost: $6,000-10,000

Typical onset: 60,000-100,000 mi

Symptoms: clunk when shifting from park to drive, excessive vibration at idle in gear, transmission feels like it's moving around under hard acceleration, visible sagging of transmission tailshaft

Fix: The rubber mounts turn to mush. Front and rear trans mounts plus engine mounts should all be inspected together. Trans mounts alone are 2-3 hours on a lift. Don't skip the transfer case mount if equipped with 4WD.

Estimated cost: $500-900

Symptoms: hard starting after sitting, sputtering under load, loss of power at highway speeds, fuel smell from tank area, visible rust around fuel filler neck

Fix: Steel fuel lines rust from inside out, especially if the vehicle sat or saw ethanol fuel early in life. Fuel filter should be changed every 20k but many owners skip it. Filter replacement is 1 hour, but if lines are compromised you're chasing rust particles through injectors and pump. Budget for pump and full line inspection.

Estimated cost: $400-1,800