O - other possible causes

I - most probable cause

problem
Causes	external leakage	internal leakage		poor circ-ulation	Over-heating	Over-flow loss	Cor-rosion	temp-erture too low	water pump noise
Hose leaking	I				I
Water pump leaking	I				I
Damaged gasket	I	I			I
Leaking heater core	I				O
Cracked cyl. block	I	I			O
Faulty pressure cap	I	I			I	I
Oil fittings loose	I	I			O
Faulty head gasket	I	I			O
Loose head bolts	I	I			O
Cracked valve port		I			O
Cracked cylinder wall		I			O
Leaking oil cooler		I
Low coolant level				I	I
plugged radiator hose				I	I
Fan belt loose				I	O				O
Bottom hose leaking	O			I
Faulty thermostat				I	I			I
Pump impeller broke				I					I
Plugged radiator				I	I
Plugged water jacket				I
Ignition timing off					I
Temp. gauge wrong					I			I
Excessive idling					I
Frozen coolant					I
Vac bypass faulty				O	I
Overfilling						I
Blown head gasket	O					I
Coolant foaming						I
No rust inhibitor				O	O		I
Anti freeze too old				O	O		I
high mineral content				O	O		I
Sending unit faulty								I
Heater controls faulty				O				I
Defective seal									I
Bearing corroded									I

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