When summer arrives and temperatures climb, two systems in your car become absolutely essential: the air conditioning that keeps you comfortable and the cooling system that keeps your engine from overheating. Both need attention before the hot weather hits.
A car that overheats on a scorching day can leave you stranded. An air conditioning system that blows warm air makes every journey miserable. Neither problem happens overnight. With a bit of preparation, you can avoid both.
Why Summer is Hard on Your Car
Your engine produces an enormous amount of heat just by running. The cooling system works constantly to carry that heat away and keep the engine at a safe temperature.
In cool weather, this is easy work. The outside air helps cool the radiator, and the engine rarely comes close to overheating even in traffic.
Summer is different. When the air temperature is already 25 or 30 degrees, the cooling system has to work much harder. Add in traffic jams, where there is no airflow through the radiator grille, and you have conditions that can push a marginally healthy cooling system over the edge.
At the same time, your air conditioning is working flat out. The compressor puts extra load on the engine, generating even more heat. The condenser, which is like a second radiator for the air con, adds more heat to the engine bay.
A car that has been fine all winter can suddenly start showing problems when the temperature rises. The best approach is to check everything before you need it.
Preparing Your Cooling System
The cooling system keeps your engine at around 90 degrees Celsius, regardless of how hot it is outside. It consists of several parts that all need to be working properly.
Coolant. The mixture of antifreeze and water that circulates through your engine and radiator. Despite the name, antifreeze protects against overheating as well as freezing. Check the level in the expansion tank when the engine is cold. The coolant should be between the minimum and maximum marks.
Coolant also needs to be the right strength. Over time, water evaporates and the mixture changes. A garage can test the coolant strength with a simple tool called a refractometer. If the mixture is wrong, it will not protect against boiling or freezing as well as it should.
Hoses. Rubber coolant hoses connect the radiator, engine, and heater. Over time, they can become brittle, soft, or develop cracks. A split hose dumps coolant rapidly and can leave you stranded. Squeeze the hoses when the engine is cold. They should feel firm but flexible, not rock hard or mushy.
Radiator. The radiator is the large grille at the front of your car. Check it for damage, blockages, or bent fins. Road debris, insects, and leaves can clog the front, reducing airflow. A gentle clean with a garden hose can make a noticeable difference.
Radiator cap. The cap maintains pressure in the cooling system, which raises the boiling point of the coolant. A faulty cap that does not hold pressure allows the coolant to boil at a lower temperature. Caps are cheap to replace if yours is old or damaged.
Cooling fan. When you are stuck in traffic, there is no air flowing through the radiator. The electric cooling fan kicks in to keep air moving. You can test it by running the engine until it reaches normal temperature, then watching to see if the fan comes on. If it does not, the fan motor, fuse, or temperature sensor may be faulty.
Water pump. The water pump circulates coolant through the system. A failing pump often makes a whining or grinding noise, or you might see coolant leaking from the pump area. Water pump failure leads to rapid overheating.
Signs Your Cooling System Needs Attention
Do not wait for your car to overheat on the hottest day of the year. Watch for these warning signs:
The temperature gauge climbs higher than usual, especially in traffic. Normal is usually around the middle of the gauge.
You need to top up coolant frequently. The cooling system is sealed, so coolant should not disappear. If you keep adding fluid, there is a leak somewhere.
There is a sweet smell from under the bonnet. This is the distinctive smell of antifreeze. It often indicates a leak.
You can see coolant puddles under the car after it has been parked.
The heater inside the car blows cold air when set to hot. This can indicate low coolant or a blocked heater matrix.
Steam comes from under the bonnet. This is serious. Pull over safely, turn off the engine, and do not open the bonnet until everything has cooled down.
| Component | What to Check | Warning Signs |
|---|---|---|
| Coolant | Level, colour, strength | Low level, rusty colour, sweet smell |
| Hoses | Firmness, cracks, leaks | Soft spots, visible damage, wet areas |
| Radiator | Airflow, blockages, damage | Bent fins, debris buildup, leaks |
| Fan | Operation when hot | Does not run in traffic, overheating |
| Water pump | Leaks, noises | Whining sound, coolant drips |
Preparing Your Air Conditioning
Air conditioning is not just about comfort. In very hot weather, it helps you stay alert and concentrate on driving. A car with functioning air con is safer than one where the driver is overheated and uncomfortable.
Regas the system. Air conditioning refrigerant slowly escapes over time. If your air con does not blow as cold as it used to, it probably needs regassing. This involves recovering any remaining refrigerant, checking for leaks, and refilling with fresh refrigerant and lubricating oil. Most cars need this every two to three years.
Run the air con regularly. Even in winter, run the air conditioning for ten minutes each week. This keeps the seals lubricated and prevents the compressor from seizing. It also helps demist the windscreen faster.
Check the cabin filter. The pollen filter or cabin air filter cleans the air before it enters the car. A clogged filter reduces airflow and makes the air con work harder. Replacing it improves both cooling and air quality. This is usually a simple job that can be done during a service.
Look for strange smells. A musty or mouldy smell when you turn on the air con indicates bacteria growing in the system. An air con antibacterial treatment can fix this and make the car much more pleasant to be in.
Listen for unusual noises. Clicking, grinding, or squealing when the air con kicks in could indicate compressor problems. Catching these early is important because air conditioning compressors are expensive to replace.
When to Get a Pre-Summer Check
The best time to check your cooling system and air conditioning is before you need them. Do not wait until the first heatwave when garages are busy with overheated cars.
If your car is due for a service anyway, a pre-summer service is the perfect opportunity to have everything checked. A full service includes coolant and fluid level checks, and you can ask for an air conditioning inspection at the same time.
If you are planning a long journey in summer, a vehicle check beforehand can give you peace of mind. Hot motorway driving with a fully loaded car puts maximum stress on both the cooling system and air conditioning.
What to Do If Your Car Overheats
Even with preparation, things can go wrong. If your temperature gauge rises into the red or you see a warning light:
Turn off the air conditioning. This reduces the load on the engine.
Turn the heater to maximum. This sounds counterintuitive, but the heater is effectively a second radiator. Running it full blast helps remove heat from the engine.
If the temperature keeps rising, pull over safely as soon as you can. Turn off the engine and wait for it to cool down. This might take 20 minutes or more.
Do not open the bonnet immediately. The engine and cooling system will be extremely hot, and coolant under pressure could spray out.
Once everything has cooled, check the coolant level. If it is low, you can add water as an emergency measure to get to a garage, but the system will need proper coolant as soon as possible.
Get Summer-Ready in East Ham
At First Auto Centre in East Ham, we can check your cooling system and air conditioning to make sure you are ready for summer. Our professional car servicing includes fluid checks and system inspections, and we can regas air conditioning systems and diagnose any cooling problems.
Do not let the summer heat catch you out. Book your car in for a seasonal check and enjoy the warmer months with confidence.
First Auto Centre, 1 Lawrence Road, East Ham, London E6 1JN. Expert vehicle care from mechanics with over 20 years of experience.
