Cooling Systems & Cabin Heat

No heat is a safety fault, not a comfort complaint

A car that will not blow hot air in Milwaukee is a car whose windshield will not clear, and that is a visibility problem before it is a comfort one. The usual causes are a thermostat stuck open so the engine never reaches temperature, a low coolant level from a slow leak, a blocked heater core, an air pocket in the system, or a failed blend door actuator - which is not a cooling fault at all but presents identically.

Those have wildly different prices, and this is a repair where guessing is expensive. A thermostat is a modest job. A heater core is often a dashboard-out job. Diagnosing which one you actually have before ordering parts is the whole game.

Antifreeze is not a fill-and-forget fluid

Coolant's freeze protection and its corrosion inhibitors both degrade with time, and the inhibitors usually go first. Old coolant with spent additives quietly eats water pump seals, radiator end tanks and heater cores from the inside. Then it leaks, and everyone blames the part rather than the fluid.

A freeze-point test takes two minutes with a refractometer, and it tells you both how cold your coolant will survive and roughly what condition it is in. We do it free on any visit here, because a car in this city with coolant good to only 10 degrees is a cracked block waiting for the right night.

Overheating in summer, and why it looks different here

Temperature that climbs in stop-start traffic on the Marquette Interchange and falls once you are moving is airflow - a cooling fan, its relay or its control circuit. Temperature that climbs at highway speed is flow or capacity - a failing water pump, a blocked radiator or a stuck thermostat. Those two symptoms send you in opposite directions.

A car that overheats is one of the few where a mobile mechanic saves you real money, because the drive to a shop is exactly what turns a $300 repair into a warped head. Stop, call, and let us come to it.