CarCare

An overheating car can make anyone hot under the collar. The old cliché "heat kills" especially applies to engines: high temperatures make hoses and gaskets brittle, can cause cylinder heads to distort, and create other unhappy problems. Granted, some heat is needed during start-up to burn off condensation that accumulates while the vehicle isn't running (which explains thermostats, EGR valves, and such). But once the vehicle is warmed up, excessive heat becomes the engine's archrival.


Cooling systems operate at a specific pressure. This raises the coolant's boiling point. When the system's intended pressure is exceeded, the spring in the radiator cap is designed to retract, allowing coolant to pass into the overflow "puke" tank and pressure to be relieved. When too much coolant bypasses into the overflow tank, boil-over occurs.

Inspection The old cliché "heat kills" especially applies to engines.
The cooling system is largely an out-of-sight, out-of-mind scenario: Most drivers ignore it until the temperature gauge goes into the red, the car overheats or won't start in the winter, or a green puddle forms on the garage floor. But just as tire pressure and oil level should be checked regularly, the cooling system needs periodic attention.


After every oil-dipstick inspection, give the cooling system a glance. Look for cracks or bulges in the heater and radiator hoses, especially near the clamps (see Tip 8). Hose clamps should be snug enough to seal the hose to the metal or plastic nipple, but not so tight that the metal band cuts into the rubber. Also look for signs of chaffing anywhere a hose touches or comes close to a metal or moving part.


Next, eyeball the coolant's color. Depending on the vehicle manufacturer's recommendation, the coolant should be neon green, pink or orange. The photo above shows a truck that had no antifreeze in the system, only water. Rust formed, a leak sprung, and the fan liberally dispersed the iron-oxide-color fluid over the engine compartment and front suspension. Which brings us to the subject of leaks.

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Photo Guide

Cooling-system problems can happen in a variety of places. Best-case-scenario cooling problems are ones that happen outside the engine block. (Courtesy Prestone)

Begin leak-detection inspection at the radiator. Look for signs of moisture around all hose fittings. (This leak was added for effect.)

Heater hoses are another each-to-check source of coolant leaks. This particular Buick 400 engine has heater-hose connections at the firewall, engine block and mid-engine.

A bad thermostat gasket or a 'stat that isn't properly seated can cause leaks here, as can the heater-hose port at the upper left. While in this area, check the water pump for leaks and giggle the fan shaft. If it wobbles, the water pump's days are numbered.

The radiator cap is another possible leak point. If its rubber gasket is cracked or chipped (like the one on the right), the cap could leak, even though its pressure valve is functioning properly. A new cap is cheap insurance.

While the cap is off, check coolant level, the color of the coolant (if visible; if not, top it off with water), and clean any deposits on the radiator's neck. The radiator core, heater core and radiator overflow tank are other possible sources of coolant leaks.

On-block leak points include the freeze plugs. A trail of "tears" leading down from a freeze plug means that the plug should be chipped out and replaced with a new one that's coated with a sealant.

Many engines have drain plugs. Leaks here can usually be fixed by removing the plug and sealing its threads with either pipe dope or Teflon tape before reinstallation.

Bulging hoses such as this pregnant radiator one foreshadow problems. Also, clamps should be snug but shouldn't dig into the rubber, which hastens cracks and bulges.

Cooling system test kits attach to the radiator in place of the cap. Its thermometer helps troubleshoot thermostat and electric fan problems. Also, the hand pump allows pressure to be applied to the system to check for external leaks; the vacuum gauge reveals internal engine leaks.

Thermostats can be checked in the kitchen with a pot of water and a thermometer. The 'stat's spring should retract at its specified temperature. Temp-gauge sending units can be checked similarly, but using a multimeter.



Related Articles
Winter Car Care & Antifreeze
Radiator and Cooling System Flush
Changing Your Air Filter
Water Pump Basics
Keep Your Eye on the Thermostat


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