Car Overheating on the Road: What to Do First, and When to Call a Tow

You're driving along, and the temperature needle starts creeping past the middle. Maybe there's a sweet smell, maybe steam off the hood, maybe nothing but a dash light. What you do in the next minute decides if the bill is for a hose or for an engine. Heat is what kills engines, and it works fast.

The first things to do

The moment the gauge heads for hot or the warning light comes on, start getting off the road. Don't wait to see if it settles down. Metal parts inside an engine expand with heat, and an engine that's far too hot can warp a cylinder head, blow a head gasket or seize outright. Those are repairs you don't want to meet.

• Turn off the AC. It adds load to the engine.
• Turn the heater on full blast with the fan up. It's uncomfortable, but it pulls heat out of the coolant and gives the engine a little relief while you find a place to stop.
• Signal, pull over somewhere safe and level, and shut the engine off.
• Turn on your hazard lights, especially at night or on a shoulder with traffic.
• Leave the hood alone for a while. Pop it from inside to let heat escape if you like, but stay back from the front of the car if you see steam.

What not to do

Never open the radiator cap or the coolant reservoir cap on a hot engine. The system runs under pressure, and the coolant is well above boiling. Opening it can spray scalding liquid and steam into your face and hands. Wait until the engine is cool to the touch, which can take a good while, and even then, crack the cap slowly with a rag over it.

Don't pour cold water onto a hot engine either. Rapid cooling on hot metal can crack parts. And don't start the car back up to see if it's "fine now." If it overheated once, something is wrong, and running it again is how a cheap fix turns into a costly one.

What usually causes overheating

Your cooling system is a loop. The water pump moves coolant through the engine, where it picks up heat. The thermostat decides when coolant flows out to the radiator. The radiator, with help from the fan, sheds that heat into the air, and hoses connect everything. A fault in any of those pieces can cause the same symptom on the gauge.

• Low coolant from a leak at a hose, the radiator, a clamp or the water pump
• A radiator that's clogged inside or cracked, often at the plastic tank
• A thermostat stuck closed, so coolant never reaches the radiator
• A cooling fan that isn't turning on, which shows up as heating in traffic but not at highway speed
• A failing water pump
• A worn radiator cap that can't hold pressure
• In the worst case, a head gasket leaking combustion gas into the coolant

You don't need to diagnose it yourself, but what you noticed helps. Did it overheat in stop-and-go traffic or at speed? Did you see a puddle under the car, and what color was it? Coolant is commonly green, orange or pink and has a sweet smell. Was there white steam, or did the heater suddenly blow cold? Is the coolant reservoir empty? Those details point a technician toward a leak, a stuck thermostat or a fan problem much faster than "it got hot."

How a shop finds the problem

The standard first step is a pressure test. The cooling system gets pressurized, and a leak shows itself with a drip, a seep or a drop on the gauge. From there the technician checks hoses, the thermostat, the fan operation and the water pump, and looks for signs of coolant in the oil or exhaust if a head gasket is suspected. Once the cause is found, the repair might be a hose, a radiator replacement, a new thermostat or pump, followed by refilling and bleeding the system so no air pocket is left behind.

El Mecanico Auto Repair handles radiator and cooling system repair and replacement in-shop. Ask them what they find in your car's cooling system before you agree to a part.

When to call for a tow

Short answer: if the car overheated and you don't know why, call a tow. Driving a few more miles to "make it home" is a common way an overheating scare becomes an engine replacement. Call if any of these apply:

• The gauge is in the red or the warning light is on after you stopped and let it cool
• You can see coolant dripping or pouring out, or the reservoir is empty
• There's steam or a sweet smell coming from the engine bay
• The car overheats again soon after you restart it
• You're on a highway shoulder, in bad weather, or after dark

Winter doesn't give you a pass. Low coolant and weak antifreeze are problems in the cold too, and the engine still makes plenty of heat on a 10 degree morning.

Stuck in Green Bay with a hot engine

El Mecanico Auto Repair at 1644 Main St, Green Bay, offers towing, local and long-distance, and will take the car to the shop for diagnosis and repair. Call (920) 217-5911, tell them where you are and what the car did, and they'll tell you what to do next. Keep the engine off while you wait.