2000 GMC ENVOY

Typical onset: 80,000-130,000 mi

Symptoms: External coolant leak at front or rear of engine valley, Coolant mixing with oil creating milky sludge on dipstick, Overheating or slow coolant loss, White smoke from exhaust if coolant enters cylinders

Fix: Replace lower intake manifold gaskets with updated composite design (avoid Fel-Pro permadry failures), flush cooling system completely. If caught late, this leads to bearing damage and total engine rebuild. 6-8 hours labor for gaskets alone, 25-35 hours if engine internals are compromised.

Estimated cost: $800-1,200 for gaskets only; $3,500-5,500 if engine needs bearings/machine work

Typical onset: 90,000-150,000 mi

Symptoms: Transmission fluid leaking from radiator area, Pink milkshake appearance in coolant reservoir (trans fluid in coolant), Coolant in transmission (cherry-colored fluid, slipping), Sudden transmission failure after coolant cross-contamination

Fix: Replace cooler lines and fittings at radiator, flush both cooling and transmission systems. If coolant entered transmission, requires full transmission rebuild or replacement. 2-3 hours for lines, 12-16 hours for 4L60E rebuild.

Estimated cost: $300-500 for lines only; $2,200-3,200 for transmission rebuild

Typical onset: 100,000-140,000 mi

Symptoms: Clunking when shifting from Park to Drive or Reverse, Excessive vibration at idle in gear, Visible sagging of transmission tailhousing, Driveline vibration under acceleration

Fix: Replace transmission mount and inspect crossmember for cracks (common on 2WD models). Often paired with worn driveshaft carrier bearing if 2WD. 1.5-2 hours labor.

Estimated cost: $250-450

Typical onset: 110,000-160,000 mi

Symptoms: Hard starting when engine is hot, Rough idle with misfire codes on multiple cylinders, Loss of power under load, Fuel pressure drops after sitting (leaking poppets)

Fix: Replace entire Central Sequential Fuel Injection (CSFI) assembly with updated MPFI unit, requires upper intake removal. 4-5 hours labor.

Estimated cost: $600-900

Typical onset: 120,000-180,000 mi

Symptoms: No-start with no fuel pressure, Stalling when fuel level drops below half tank, Whining noise from fuel tank area, Erratic fuel gauge readings

Fix: Drop fuel tank and replace pump module assembly. Often find corroded wiring at tank connector. 2-3 hours labor.

Estimated cost: $450-700

Typical onset: 80,000-140,000 mi

Symptoms: Service 4WD light illuminated, 4WD will not engage, Grinding noise from front axle when engaging 4WD, Binding in tight turns even in 2WD mode

Fix: Replace thermal actuator on front axle or axle disconnect motor and seal. Clean connections and re-grease splines. 2-3 hours labor.

Estimated cost: $300-550

Typical onset: 100,000-160,000 mi

Symptoms: Oil spots on driveway centered under bellhousing, Oil coating on transmission bellhousing, Visible oil seepage at oil pan rail, Low oil pressure warning if level drops significantly

Fix: Rear main seal requires transmission removal, oil pan gasket needs crossmember drop. Both often done together. 6-8 hours combined labor.

Estimated cost: $700-1,100