Chevrolet 2005 Astro Owner's Manual page 337

100,000 Miles (166 000 km)
Inspect spark plug wires. An Emission Control
Service.
Replace spark plugs. An Emission Control Service.
If you have not used your vehicle under severe
service conditions listed previously and, therefore,
have not changed your automatic transmission fluid,
change both the fluid and filter.
Change transfer case fluid.
Inspect Positive Crankcase Ventilation (PCV) valve.
An Emission Control Service.
150,000 Miles (240 000 km)
Drain, flush and refill cooling system (or every
60 months since last service, whichever occurs first).
See Engine Coolant on page 5-26 for what to use.
Inspect hoses. Clean radiator, condenser, pressure
cap and neck. Pressure test the cooling system
and pressure cap. An Emission Control Service.
Inspect engine accessory drive belt. An Emission
Control Service.
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