Cooling System Problems and Possible Causes

[CaffeineTripp]

Cooling Symptoms

1: Temperature Gauge Reads Hot at Idle and at Speed (70%+ on gauge)

Possible Causes:

Thermostat stuck closed
Low Coolant
Blockage in radiator
Collapsed Radiator Hose(s)
Water Pump Seized
Major leak in cooling system


2: Temperature Gauge Reads Normal at Idle, drops at low cruising (40%- on gauge)

Possible Causes:

Thermostat stuck open
Faulty Temperature Gauge Sender
Cooling Fan(s) Consistently On


3: Temperature Gauges Reads Normal at Idle, at Speed, luke-warm heat

Possible Causes:

Air Bubbles in Cooling System
Thermostat Failing
Thermostat Stuck Open with Heater always on
Small coolant leak at thermostat housing
Heater Core Blocked
Heater Core Hoses Blocked
Blend Doors Stuck Shut


4: Lower Radiator Hose Hot, Upper Significantly Cooler

Possible Causes:

Water Pump failure
Blockage in Radiator


5: Heater Core Inlet Hot, Heater Core Outlet Cold with Heater Off

Possible Causes:
Heater Core Blocked
Heater Hose Blocked
Collapsed Hose(s)


6: Temperature Gauges Reads Hot at Idle, Normal at Low RPM Cruise

Possible Causes:
Cooling Fan(s) not turning on
Faulty Coolant Temperature Sensor
Water Pump Failure


7: Erratic Coolant Temperature Sensor Readings

Possible Causes:
Air bubbles in cooling system
Faulty Temperature Gauge Sender


8: Overflow Tank Bubbling/Radiator Fill Neck Bubbling or Smelling Bitter/of Exhaust

Possible Causes:
Blown head gasket(s)

9: Metallic/Black 'Floaties' in Coolant

Possible Causes:
Water Pump failure
Radiator/Heater Core aluminum breaking down
Cooling Hose(s) breaking down

10: Coolant is Milky/Sludge-y/Smells Burnt

Possible Causes:
Blown head gasket(s)
Radiator/Transmission line failure (A/T only)


A proper cooling system will have coolant that is a 50/50 mixture of antifreeze and distilled (boiled) water. Antifreeze is essential in both cold and hot environments. Antifreeze helps keep the water from freezing in -40 F* weather and helps raise the boiling temperature of water in desert conditions. Antifreeze also helps in absorbing the heat of the engine and the transmission. Ideally, a 50/50 mix is best. But straight antifreeze or straight water is not. Consistently higher and higher readings of the temperature gauge, over months, while no coolant has leaked, burned, or steamed, have to be looked at as old coolant. Coolant breaks down and will eventually lose it's ability to retain heat as well, causing temperatures to increase.
As a side note coolant also impacts your fuel mileage. If your fuel mileage has decreased, get a complete cooling system flush. Heat retention is what your ECU's warm up cycle depends on for proper fuel mileage.

The water pump, of course, helps circulate the the coolant around the engine, heater core, and radiator. A good working water pump will not leak out of the weep hole, keep cooling system pressure, and ensure that you have optimal heat in the winter.

The thermostat is like a timed stop light. The ones that you see when you merge onto a large highway at rush hour. It opens to allow a lot of coolant to flow, and closes when the temperature cools too much. Thermostats are mechanical, therefore they can fail, and will fail. They can fail open causing a 'no heat' situation or fail closed causing a 'high temperature reading' situation. It is possible to see a gradual failure of a thermostat; high temperature reading, then going to normal operating conditions for quite some time at idle and at speed.

Cooling system hoses do break down, bulge, crack, and split due to age. Check all hoses for bulging or squishy-ness.

If I've missed anything substantial, or even something that is small that is often over looked, let me know and it'll get edited. Also, even the simplest things, like installation, proper burping of cooling system, or other how-to's let me know and they'll get done step by step.

[20b]

Thanks man, this will be useful as a reference if anything ever goes wrong with the car cooling wise!

[CaffeineTripp]

Thanks man, this will be useful as a reference if anything ever goes wrong with the car cooling wise!

Doesn't cover everything, but I think I hit most points on it.