Overheating

Temp gauge creeps into the red. Coolant boils over. Steam.

Clogged radiator cores, weak water pump, collapsed lower radiator hose, slipping fan belt, stuck thermostat, or head gasket failure (rare on these engines if not previously overheated).

1. 1 Start simple: check coolant level, inspect hoses (especially lower, should be reinforced), tighten or replace fan belt
2. 2 Verify thermostat opens (Volvo spec is typically 82°C). Test by boiling in a pot of water with a thermometer
3. 3 Flush radiator. If it's original, it's probably half-blocked with 60 years of silt and scale. Consider a re-core or replacement (IPD, FCP Euro stock reproduction units)
4. 4 Water pump: inspect for bearing play or weeping. Rebuild kits exist, but a new pump is often easier (~$80-150)
5. 5 If all else fails, pressure test the system and check for head gasket or cracked head. B18/B20 heads crack rarely, but it happens if previously cooked