Sudden Loss of Coolant and Engine Overheating Incidents. We recently surveyed the Brickboard and Swedishbricks lists for incidents of sudden loss of coolant and engine overheating. Here are the results from around thirty instances worldwide among Volvo drivers:

-Hose clamp failed; lower radiator hose parted from radiator outlet neck All the coolant suddenly drained out of the radiator,leaving only the coolant in the block. Engine required a new headgasket.

-Plastic-bodied heater water valve cracked; coolant was pumped out

In most of the incidents, drivers did not notice the loss because the coolant was pumped or blown under the car. In most cases, the first evidence was engine noise, slowing of the car, or other signs of serious engine damage.

-Heater hose fractured due to aging and internal crack; catastrophic loss of coolant

-Heater hose chaffed against block, rubbing through and failing; catastrophic loss of coolant

-Radiator plastic side tank fractured; catastrophic loss of coolant

-Radiator hose split due to aging and internal crack. Upper: loss of coolant; lower: catastrophic loss of coolant

-Top radiator hose clamp was over-tightened, cracking plastic neck outlet. Some coolant was pumped out and the engine temp gauge showed overheating but no damage occurred.

-Nobody mentioned a failed water pump as a cause of catastrophic loss-of-coolant.

In almost every case, the lack of an "idiot light" caused drivers not to notice the loss until too late. When the driver finally looked at the temperature gauge, it was invariably far into the red zone, indicating serious overheating. In almost every case, drivers attempted to drive to a convenient destination such as home, a gas station, or a freeway exit. This extended drive usually led to further engine damage. The least damage noted (except in the last instance) was head gasket; in many instances the engine required replacement.

Lessons learned:

1. Assume that your cooling system components have a limited lifespan. Replace them according to an intelligent schedule. I replace hoses every six years and the radiator and water valve at year ten. I replace the water pump either at a convenient maintenance interval or when it starts leaking at the seal. For turbo cars, assume that the higher underhood temperatures will reduce component lifetimes.

2. Give serious thought to installing a loss-of-coolant sensor and an idiot light wired into your instrument cluster. "I didn't notice until it was too late" was a universal experience.

3. If you notice smoke, fluid or other evidence of engine distress, STOP and see what the matter is before trying to go any further. Shut the engine off if you have a loss-of-coolant or oil.