Car Overheating in Summer: What to Do in Pakistan

If your car starts overheating, switch off the AC, turn the heater and fan to full hot to pull heat away from the engine, and pull over as soon as it is safe. If the gauge is in the red, steam is coming from the bonnet or a red temperature warning is on, switch the engine off and let it cool. Do not open the radiator cap on a hot engine, and do not keep driving to reach a workshop. Driving an overheated engine is how a cheap fix becomes a cylinder head or head gasket job.

Pakistani summers are hard on cooling systems. Long jams in Karachi and Lahore, AC running all day, dusty roads and steep climbs on routes such as the Salt Range on the M-2 all push engines to their limits. The good news is that most overheating gives warning signs first.

Signs your car is overheating

• The temperature needle rises above its normal position, usually the middle of the gauge.
• A red thermometer warning light or message appears on the dashboard.
• Steam or white vapour rises from under the bonnet.
• You smell something sweet, which is often hot coolant leaking.
• The engine loses power, knocks or pings, or the AC suddenly blows warm air.

Many newer cars have no needle, only a warning light, or a blue cold light that goes out when the engine warms up. Check your owner's manual so you know what your car shows.

What to do, step by step

• Switch off the AC. The compressor adds load to the engine and heat in front of the radiator.
• Turn the heater to full hot and the fan to maximum. It is uncomfortable, but it moves heat out of the engine.
• If you are in traffic, shift to neutral or park and raise the revs gently to keep the water pump and fan working, unless the gauge is already in the red.
• Pull over somewhere safe and away from traffic. On a motorway, use the hard shoulder or the next service area.
• If the gauge is in the red or you see steam, switch the engine off.
• Open the bonnet only once the steam has stopped, and keep your face away from the engine bay.
• Wait at least 30 minutes before touching the radiator cap or coolant reservoir cap.

Never open a hot radiator cap

Coolant in a hot engine is under pressure and well above boiling point. Opening the cap releases it in a jet that can cause severe burns. Wait until the top hose feels only warm when you squeeze it with a cloth, then open the cap slowly with a thick cloth, letting the pressure out before removing it fully.

Common causes of overheating

• Low coolant from a leak in a hose, the radiator, the water pump or the heater core.
• A radiator fan that does not switch on, often because of a blown fuse, a failed relay, a bad sensor or a worn motor.
• A radiator or AC condenser clogged with dust, insects and leaves, which blocks airflow.
• A thermostat stuck closed, so coolant cannot reach the radiator.
• A failing water pump, or a broken or slipping drive belt on engines where the belt drives the pump.
• Plain water instead of coolant, which boils at a lower temperature and lets corrosion build up inside the system.
• A head gasket fault, which can push combustion gas into the cooling system.

Quick checks once the engine is cool

With the engine cool and switched off, check the coolant level in the reservoir against the minimum and maximum marks. Look for wet patches or drips under the car and around the hoses. Check that the drive belt is in place. Then start the engine, let it warm up and see whether the radiator fan comes on as the temperature rises. If the fan never runs, that is very likely your problem.

If the coolant is only slightly low and there is no obvious leak, you can top up with the coolant your manufacturer recommends. In an emergency, clean water will get you to a workshop, but have the system flushed and refilled with the correct coolant soon after.

When to stop and call for recovery

• The engine overheated again quickly after you topped up.
• Coolant is pouring out, or the reservoir empties as you watch.
• There is white smoke from the exhaust, or oil on the dipstick looks milky.
• The engine knocks, runs roughly or will not restart.
• You are on a motorway or a hill road with no safe place to keep stopping.

In these cases, driving on is likely to cause serious damage. A recovery truck can take the car to your workshop, and a mobile mechanic can sometimes fix a simple fault, such as a fan relay or a split hose, where you are.

How to prevent overheating in summer

• Check the coolant level weekly in summer, with the engine cold.
• Have the cooling system flushed and refilled at the intervals in your service book.
• Ask your mechanic to clean the radiator and AC condenser fins before the hot months.
• Replace cracked or soft hoses and a worn drive belt before a long trip.
• Watch the gauge on long climbs and in traffic, and ease off early if it starts to rise.
• Carry a bottle of the correct coolant and some drinking water on long journeys.

On very hot days, check the Pakistan Meteorological Department's forecast before a long drive and plan to travel in the cooler hours of the morning or evening. Your engine, your tyres and your passengers will all cope better.