Overheating is not caused by hot weather. It is caused by a cooling system that was already marginal and had no margin left.
A cooling system in good order handles a July afternoon on I-27 without difficulty. When one overheats, the heat did not cause it — the heat removed the last of a margin that had already been eaten by something else.
What actually goes wrong
- Old coolant. Coolant has corrosion inhibitors and they deplete. Depleted coolant lets corrosion products build up inside the radiator and block passages, which is exactly the loss of capacity that shows up in August.
- A blocked radiator core. Externally, from dust, chaff and bugs packed into the fins. Out here this is extremely common and it is a five-minute inspection.
- A weak radiator cap. The cap holds system pressure, and pressure raises coolant's boiling point substantially. A cap that no longer holds means coolant boiling at a lower temperature.
- A failing water pump. Bearing noise or a weep from the drain hole is the warning.
- A stuck thermostat. Stuck closed and it overheats quickly; stuck open and it never reaches temperature.
- A failed fan clutch, which stops the fan pulling air at low speed — so it overheats in traffic and is fine on the highway.
If the gauge climbs
- 1Turn the air conditioning off and the heater on full. The heater core is a second radiator and it genuinely helps.
- 2If you are in traffic, pull over and idle rather than crawling. Airflow at low speed depends on the fan.
- 3If it keeps climbing, shut the engine off.
- 4Do not open the radiator cap on a hot system. It is pressurised and the coolant is above its atmospheric boiling point. Opening it produces a scalding release.
- 5Let it cool for at least half an hour before doing anything.
Why it matters so much
An overheat is not an inconvenience. A genuinely overheated engine can warp a cylinder head or fail a head gasket, and that is a repair on a completely different scale from a thermostat or a radiator cap.
We diagnose and repair cooling systems at the shop. If it is overheating, stop rather than pushing on to the next town, and call us once it is safe.
Need this handled today?
Bring it to the shop.
Tire, brake and full auto repair at 13209 Frankford Ave, Suite 29, Lubbock, TX 79424 — serving drivers from Lubbock, Wolfforth, Shallowater, Slaton, Idalou and the surrounding South Plains.