Engine overheating: what to do right now

Pull over now

General guidance for this symptom. A warning light that is flashing or an overheating engine: stop driving and call.

Likely causes

• Low coolant

  The system is sealed and the level should not move. If it is low, coolant has left through a hose, a clamp, a radiator seam, the water pump or a heater core. We find the leak if it is external, top off and pressure-check the system, and do a full coolant flush once the leak is sorted.

  Coolant flush and cooling system service
• A stuck thermostat

  The thermostat opens to let coolant reach the radiator. Stuck closed, the engine heats up within a few miles even with a full system. It is a small part that a repair shop replaces; we can spot the symptom, a cold upper radiator hose on a hot engine, in the bay.

  Multi-point maintenance check
• A cooling fan that is not running

  The fan matters at low speed. A car that is fine on I-580 and climbs toward the red in the Mount Rose Highway construction line has a fan, relay or sensor problem. We check whether the fan comes on with the A/C running and tell you what we saw.

  A/C service and recharge
• Old coolant and scale in the radiator

  Coolant loses its corrosion protection over years, and the deposits that form narrow the radiator passages. Long-life coolants run five years or more by manufacturer; older green coolant about two years. A flush restores flow and protection, and it is the one overheating cause that is entirely ours to fix.

  Coolant flush and cooling system service
• A head gasket or a failed water pump

  If the car overheats, loses coolant and leaves white steam at the tailpipe, or the pump bearing whines and weeps, that is engine repair. We confirm the signs and recommend a repair shop. Nobody here will flush a system that needs a gasket.

  Multi-point maintenance check

Overheating is the one problem where the next ten minutes matter more than the next ten days. An engine that runs hot once, briefly, usually survives. One that is driven to the next exit with the needle pinned often does not. The cause is almost always the cooling system: low coolant, a bad thermostat, a fan that did not come on, a leak that drained the radiator. We service cooling systems, so we can tell you a lot once the engine is cold, but the first step is yours and it is the shoulder of the road.

At a glance

• Needle in the red or steam: pull over, engine off, now
• Never open a hot radiator cap
• Heater on full can buy a mile in traffic, not a trip
• Low coolant is the usual cause; find out why it is low

On the side of the road

1. Signal, pull off, shut the engine off. Do not drive to the next exit to find shade.
2. Hood up to let heat out, but do not touch the radiator cap or the reservoir cap. The system is under pressure and the coolant is above boiling.
3. Wait until the engine is cool to the touch. In July at Reno's 90 F afternoons that can be a long while.
4. Once cool, look at the reservoir level and under the car for a bright green, orange or pink puddle.
5. If the reservoir is low and you have water, add it slowly with the engine off. That gets you a short distance, not home from Tahoe.
6. Restart and watch the gauge. If it climbs again within a mile, shut it off and call for a tow.

In slow traffic with the gauge creeping up, turning the heater to full hot and the fan high pulls heat out of the engine into the cabin. It is a stopgap for a mile of Virginia Street at rush hour, not a way to keep driving.

Why it happens on our roads

Three things set Northern Nevada apart. Altitude: coolant boils at a lower temperature at 4,500 feet than at sea level, so the margin is thinner. Grades: the Geiger Grade, the Mount Rose Highway and the climb to Spooner Summit on US-50 run the engine at full load for miles. Heat: the Reno airport averages 65 days a year at 90 F or hotter and six at 100 F or hotter (NOAA 1991-2020). A cooling system that is a little low and a little old handles Sparks in April and fails on a trailer pull to Topaz Lake in August.

The fix for all three is the same: a full, clean system with the right coolant type. Our coolant types guide explains why the color and the chemistry have to match what the manufacturer filled.

What we do once it is cold

We check the coolant level and condition, look for external leaks at hoses, clamps, the radiator and the water pump weep hole, check that the fan runs, feel the radiator hoses for flow, and test the coolant's freeze and boil protection. If the system is simply low and old, a coolant flush and cooling system service with the manufacturer's coolant type is the fix, and we do it at Mae Anne Avenue, Longley Lane, College Parkway and US 395 the same day.

If we find a leak at a hose we can reach, we tell you. If the leak is a pump, a radiator, a thermostat or a gasket, we write it down and point you to a repair shop. A flush before the repair wastes your money, so we do not sell one.