Don't get overheated this summer

Motorists sitting on £5 billion overheating time bomb

29 June 2009

With temperatures of up to 32C forecast this week, research by the AA shows that around six million motorists in the UK could be risking a four-figure repair bill by never checking their car's coolant level, meaning they and their car could boil over this summer.

An AA/Populus poll of more than 14,500 AA members found that a quarter of women respondents admit to never checking their car's coolant, compared to 10 per cent of men.

AA breakdown patrol of the year Stewart Topp

Carry plenty of drinking water

Stewart Topp, AA patrol of the year, says: "Driving in this heat can be pretty uncomfortable if you're not properly prepared. You can dehydrate quickly, so make sure you carry plenty of drinking water – at least a litre per person, not forgetting any pets. Even if your car's got aircon it's important to take sun hats and high factor sun lotion as well as water, as if your car breaks down, there is often no shade at the roadside."

With congestion likely because of the weather, it's also a good idea to make sure you have plenty of fuel – if you do get stuck, you can at least keep the air conditioning on (and it will allow you to keep the radio on to listen to Wimbledon!)

At the other end of the scale, four times as many men (28%) than women (7%) do the recommended weekly check.

Londoners least likely to check

The research shows that Welsh drivers are the best prepared with 24 per cent inspecting weekly while Londoners lag behind (14%) and are also the most likely to never check (18%).

Londoners' excuse may be partly due to ignorance with more than a fifth (22%) unaware of how to check the coolant level. Overall, nearly all men (93%) claim to know how to, compared with less than two-thirds of women (61%).

Overheating is a much bigger problem during the summer, as engines operate at higher temperatures – there isn't the cold winter air to take away a lot of the heat.

Stewart Topp, AA patrol of the year, says: "Many cars are only used on the same local trips with the engine barely reaching normal operating temperature, so the cooling system is hardly tested. However, that all changes when the car is suddenly loaded with luggage and passengers for a long holiday trip in hot weather, exposing any problems in the system.

Regular checks

"Drivers should get into the habit of regularly checking their car including the coolant level and fan. If you notice that the coolant has dropped, get it checked out, as modern cooling systems shouldn't really need topping-up between services."

Cooling fan

A seized cooling fan is the most common initial cause of overheating but the survey showed that only 6 per cent of drivers knew this.

Stewart explains the fan's importance: "When you get caught in traffic, the cooling fan will come on automatically and draw air through the radiator. If the fan motor has seized, say through lack of use, the coolant will get hotter until it boils and is lost from the system. If you don't spot this and turn off the engine, the head gasket will probably fail causing expensive damage."

If the temperature gauge does rise

If drivers notice the temperature gauge rise, the most effective way of temporarily dealing with it is to turn the heater up full and the air conditioning on. Less than a third of female drivers (30%) and half (50%) of men knew this.

Drivers in the South-west were the most clued up (49%) but those in Northern Ireland would risk the most damage (33%). More than a third of women (36%) compared to 16 per cent of men indicating that they were completely unaware of how to deal with an overheating engine at all.

Expensive repairs

Stewart concludes: "If your car overheats, at best, you'll likely have to cough up around £250 to repair the cooling fan or £1,000 for a head gasket and, at worst, several times that for a new engine. So, with a hot summer forecast, it's never been a better time to get your handbook out and spend a few minutes now to potentially save yourself a lot of money and time later."

Checking the cooling system

Coolant is a mixture of antifreeze and water in the car's cooling system.

The radiator which dissipates heat from the engine to the atmosphere is fitted with an 'expansion tank' that allows the coolant to expand under rising pressure and temperature.

The tank is usually clear plastic and marked on the side with maximum and minimum marks. It should be easy to see the level of coolant through the side of the tank.

Check the vehicle handbook for the location of the expansion tank and coolant filler cap. Follow any vehicle-specific advice given.

The coolant level should only be checked when the engine is cold.

  • Check the coolant reservoir level regularly and look out for wet or white staining on coolant hoses too. You don't have to remove the cap to check the level, simply look to see if the coolant is between the minimum and maximum marks
  • If you do need to top it up refer to the handbook first to make sure you use the correct type of antifreeze and follow the correct procedure
  • The coolant filler cap must only be removed with the engine is cold - the cooling system is pressurised and you risk a face-full of scalding hot water if you release it with the engine hot.
  • Modern cars have sealed cooling systems, so they shouldn't need topping up between services. If the level drops, the coolant must be escaping from somewhere, so it should get investigated

Checking the cooling fan

Follow this simple procedure (best done when you get home from a journey) to check if the cooling fan operates correctly as the temperature rises;

  • Set the car heater to cold and run the car to normal temperature and then allow the engine to idle for around five minutes – the fan should cut in automatically
  • Keep an eye on the temperature gauge, if the car has one – it's essential that the car isn't allowed to overheat while carrying out this test
  • If the fan doesn't come on there may be a fault with the fan temperature sensor, the wiring or the fan itself


Read more summer motoring advice »

The AA has produced a video guide to checking your coolant level, available to download as a podcasts.

To help its members avoid problems, the AA has teamed up with Nationwide Autocentres to offer them free pre-summer car checks (a 15-point maintenance inspection available to AA members only).

AA/Populus panel research: 14,743 AA members interviewed online between 1-8 May 2009.


30 June 2009