1998 GMC Sonoma Owner's Manual - Page 363
1998 GMC Sonoma Manual
Page 363 highlights
Long Tripmighway Maintenance Schedule 150,000 Miles (240 000 km) 1 I DATE MILEAGE 0 Drain, flush and refill cooling system (or every 60 months since last service, whichever occurs first). See"Engine Coolant" in the Index for what to use. Inspect hoses. Clean radiator, condenser, pressure cap neck. Pressure test and the cooling system and pressure cap. An Emission Control Service. 7-41
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