Engine Overheating in Thailand: What to Do

If the temperature gauge climbs into the red, a warning light comes on, or steam appears from under the bonnet, stop as soon as you can do it safely, switch the engine off and leave it alone. Almost all the serious damage from overheating happens in the minutes after the driver notices and keeps going — "just to the next town" is how a cooling problem becomes a cylinder head.

Thailand pushes cooling systems harder than most places a visitor drives: high ambient temperatures, stop-start traffic in cities, long climbs on the northern mountain roads, and a lot of hire vehicles whose coolant was last thought about some time ago.

• If it overheatsStop, switch off, wait
• The mistake that costs an engineDriving on, or opening a hot cap
• Highway Police1193

The warning signs, in order of severity

• The temperature gauge sitting higher than usual — the earliest sign, and the one people ignore. Learn where your needle normally sits in the first hour of driving a strange vehicle.
• Air conditioning going warm while the engine is under load. Often the first symptom a driver actually notices.
• A sweet, syrupy smell. That is coolant, and it means you are losing some.
• Steam or vapour from the bonnet shut line, or from the front of a motorbike.
• The gauge in the red, or a red warning light. Stop now.
• Loss of power, pinking, or the engine running roughly. Damage is already happening.

What to do at the roadside

1. Turn the air conditioning off and, if you cannot stop immediately, turn the heater on full and open the windows. It is deeply unpleasant in Thai heat and it genuinely dumps heat out of the engine.
2. Get off the road, using hazard lights, ideally to a shaded spot off the tarmac.
3. Switch the engine off. There is an argument for idling briefly to circulate coolant, but it depends on the fault, and for a driver who cannot diagnose it, off is the safe answer.
4. Open the bonnet if you can do it without reaching over a steaming engine, and step back. Do not touch anything.
5. Wait. Thirty minutes minimum, longer in the sun. Get into the shade yourself and drink something.
6. Look, once it is cool. Is the expansion tank empty? Is there coolant on the ground or sprayed over the engine bay? Is a hose split or off? Is the radiator packed with insects and dust? Has a fan belt broken?
7. Call. The rental company if it is a hire vehicle, your insurer if you own it. On a highway, 1193; on a motorway, 1586 press 7; on a Bangkok expressway, 1543 option 1.

The mistakes that turn this into a new engine

• Driving on. An engine run hot enough to warp a head or blow a head gasket is a repair measured in tens of thousands of baht. Recovery costs a fraction of that.
• Opening the cap hot. A scald injury on top of a breakdown.
• Pouring cold water into a hot engine. Thermal shock can crack a hot cylinder head or block. If the engine is hot, wait; if you must add water to a warm engine, add it slowly with the engine idling.
• Topping it up and forgetting about it. Coolant does not disappear on its own. If the level was low, something is leaking, and it will happen again in an hour, probably somewhere less convenient.

Why it happens here

Traffic

Stationary traffic in 35-degree heat is the hardest thing you can ask of a cooling system, because there is no airflow through the radiator except what the fan provides. If the fan is not working, a car that is perfectly happy at 90 km/h will overheat in a Bangkok jam within minutes. That is why an overheating problem often appears for the first time in city traffic — see Bangkok rush hour for how long you can expect to be sitting.

Climbs

Long ascents at low speed in a low gear load an engine heavily while producing modest airflow. The northern mountain roads, the climbs on the islands and the hills behind Phuket all do it. Mountain roads and hairpin bends covers the driving; the cooling point is simply to watch the gauge on a long climb and back off if it starts to move.

Neglect

Radiators clogged with insects and dust, coolant that is old and no longer inhibiting corrosion, a fan that has failed and nobody noticed because the vehicle mostly moves. This is the common cause on cheap hire cars and on bought-second-hand vehicles, and it is worth a look at the expansion tank level before you set off on a long drive.

Motorbikes

Most small Thai scooters are air-cooled or fan-cooled and rarely overheat in normal use, though they will get very hot sitting in traffic and can suffer on long climbs with a heavy pillion. Larger and more modern machines are liquid-cooled and have the same failure modes as a car: a leaking hose, a low coolant level, a failed fan. The signs are the same — a temperature light, loss of power, a smell — and so is the answer: stop, switch off, wait, and do not open anything hot.

One extra point that belongs here: an air-cooled engine that has been sitting in traffic is very hot indeed, and the exhaust and cylinder are the classic source of a scooter burn to a calf or ankle. Road rash and exhaust burns explains why those wounds go bad quickly in this climate.

Getting it fixed

On a hire vehicle, ring the company and let them arrange it. Mechanical failure of their vehicle is normally their problem — but damage caused by continuing to drive an overheating engine may not be, and that is another reason to stop when you first see the gauge move.

On your own vehicle, a Thai garage will deal with hoses, radiators, fans, thermostats and water pumps quickly and cheaply; these are ordinary parts on ordinary vehicles. Agree the price before work starts, and if a head gasket is being discussed, get a second opinion before agreeing to it. Roadside assistance in Thailand: who to call covers recovery.

Frequently asked questions