A radiator leak is more than just a nuisance. It can lead to overheating and cause permanent damage to your engine. If you suspect you have a leak then the following tips can help, but if you aren’t particularly mechanically minded you would be wise to take your car to a mechanic – or have your ACE Mechanic come to you! – to have your cooling system tested.
The radiator, the hoses that are connected to the radiator and cooling system may be very hot and or under pressure. Remember, whenever you are near a hot radiator that is under pressure, do not remove a radiator cap until the engine has completely cooled down or you could scald yourself with boiling water or coolant.
Signs of a leak
Coolant leaks can occur in a number of areas, and all need to be inspected for tell-tale signs. If the coolant level has been going down or your temperature gauge has been going up, but you haven’t seen any evidence of a leak, then you should try the following.
Open the bonnet and visually inspect the engine bay and radiator for any signs of leaking fluid. The radiator can develop leaks around the upper and lower hose connections due to constant vibration, so check the hose fittings to make sure they are tight and there are no splits or cracks in the hoses. If a hose is soft and squishy or hard and brittle, it may have perished and be leaking.
The radiator itself is often subjected to stones and debris flying up into it and this may have caused a hole or crack to form, resulting in a leak. Old radiators are also subject to rust, so look for signs of rust or corrosion on the outside.
As mentioned, the radiator cap is another area where leaks can occur. If it is not maintaining pressure in the radiator, it can cause the engine to overheat and lose coolant.
Another part of the cooling system where coolant can be lost is the overflow reservoir. In most modern cars, this is pressurised, so if it is cracked or leaking, the system will lose coolant every time the engine heats up.
Check under the car as well for any signs of coolant on the driveway or garage floor. It is usually a bright green colour, so it won’t be hard to miss. If you find a puddle, look at the part of the engine directly above it and you’ll probably have found the source of your leak.
Repairing a leak
If you find an obvious leak then you may be able to repair it yourself, depending on where and how bad it is. You can temporarily tape a leaking hose with electrical or duct tape until you are able to get a new one. A bottle of cooling system sealer added to the radiator will also seal minor internal holes and cracks for a while, but these are very temporary measures and proper repairs or replacement of parts is necessary to ensure the leak is fixed for good.
Another thing you can try is to pressure test your cooling system. If it is not holding correct pressure, this may be what is causing your engine to overheat. A pressure tester is a tool that attaches to the radiator filler neck and has a pressure gauge and hand pump.
Simply pump the cooling system up to the recommended pressure (this will be on your radiator cap) and then wait ten to fifteen minutes. If the cooling system loses pressure during this time then you have a leak and, if you can’t see any evidence of it, it is probably an internal leak and will require professional repair.
Radiator caps can also lose their ability to hold pressure over time, so if you suspect this to be the case, or if it is an old cap in poor condition, replacing it could be a cheap solution to your problem.
Another thing to remember when repairing a cooling system leak is that air pockets can form in the system, which can cause further overheating. You will need to make sure all the air is out of the system when you refill it with coolant, and you can do this either by using the bleeder valves installed on some systems or, if it is an older car, by loosening one of the lower hoses a little until all the air is out of the system. It is very important the cooling system is bled properly.
Preventing a leak
Prevention is always better than cure, and in the case of cooling system leaks a little vigilance could save you a lot of money in expensive repairs to your engine. To reduce the likelihood of a leak occurring, you should:
- Regularly check the coolant level and top it up if required.
- Be aware of your car’s temperature gauge and check it regularly.
- Have your radiator and cooling system pressure-tested and flushed every so often as part of your routine vehicle maintenance.