Coolant Leak: Signs, Causes and Repair
Written by Petro Olekhnovych, mobile mechanic in Aylesham, Kent
The main coolant leak signs are a coloured, sweet-smelling puddle under the front of the car, a coolant level that keeps dropping, and a temperature gauge or warning light showing the engine is running hot. The RAC lists a coolant leak as not safe to drive on, because the engine can overheat and suffer serious damage. If you spot these signs, get the car checked before you make any long journeys.
The signs of a coolant leak
Coolant (often called antifreeze) is the liquid that carries heat away from your engine. When it escapes, you usually notice one or more of these:
A puddle under the front of the car. The RAC says coolant can be green, yellow, pink, blue, red or even clear with a coloured tinge.
A sweet smell. The RAC describes it as a sweet smell, like candyfloss. Coolant also feels slightly thicker and stickier than water.
A level that keeps falling. The AA says modern sealed systems rarely need topping up unless there is a leak.
Wet or white staining around hoses and the engine, which the AA says can point to future problems.
A heater blowing cold air even on the hot setting, which the AA links to low coolant.
Warning lights. On many cars an amber light means the coolant level is low, while a red light means the engine is overheating. Check your handbook for what your car’s lights mean.
Is it water or coolant?
Clear water dripping under the car on a warm day is often just air conditioning condensation, which the AA says is usually harmless. Water is clear and has no smell. Coolant is coloured, sweet-smelling and a little sticky.
What causes a coolant leak?
Coolant runs through a lot of parts, so there are several places it can escape. Causes mentioned by the RAC and AA include:
The radiator. The RAC says this is the most common source.
A faulty or loose radiator cap, or a loose connection.
Hoses, clamps and seals. The RAC notes older cars are more prone to these leaks.
A cracked coolant reservoir (expansion tank).
The heater matrix (heater core) behind the dashboard. The AA says this can leave coolant on the floor inside the car and a sweet smell in the cabin.
The water pump. If the leak seems to come from the pump area, read our guide to water pump failure symptoms.
When the leak is inside the engine
Sometimes coolant disappears with no puddle at all. One possible cause is a failed head gasket. The AA lists these signs: white exhaust smoke, a sweet smell from the exhaust, a milky or white colour on the dipstick or under the oil filler cap, loss of power and regular overheating. The AA does not recommend driving with a blown head gasket. If you see milky oil, stop driving and get it checked.
Engine problem or belt due?
Timing belts, water pumps, coolant and fault finding done at your door.
WhatsApp for a free quote Call 07563 350335
Labour £30 to £50 per hour depending on the job. Send your reg number and we will reply with a price before any work starts.
Is it safe to drive with a coolant leak?
Usually no. The RAC warns that even a small leak can lead to overheating, and repeated overheating can cause major engine damage. The AA says overheating is the most common cause of head gasket failure.
If the temperature gauge climbs or a red coolant light comes on while you drive, pull over when it is safe and switch off the engine. Do not carry on. Our guide to what to do when your car is overheating explains the next steps.
Never open the coolant cap on a hot engine. The system is under pressure and hot coolant can scald you. The AA says to wait at least 30 minutes after switching off, and longer if the engine has overheated.
Can I just top it up?
Topping up can get you to a safe place, but it does not fix the leak. A few points from the AA and RAC:
Fill to between the min and max marks on the expansion tank.
Use the coolant type your handbook specifies. The AA says different types do not mix well, and some cars need pre-mixed coolant.
Use plain water only in an emergency to reach help. It dilutes the coolant, and the AA warns that weak coolant can freeze in winter and damage the engine.
Keep pets away from spills
Cats Protection says the ethylene glycol in antifreeze tastes sweet and that even a tiny amount can be fatal to a cat. Clean up any spill, and do not leave drained coolant in an open container. If you think a pet has swallowed some, go to a vet straight away.
What does a coolant leak repair cost?
There is no single price, because the repair depends on where the leak is. A loose clip or cap is a small job. A radiator, water pump or heater matrix takes more time and more expensive parts. A head gasket is a much bigger job again.
The things that affect cost are:
Which part has failed and the price of that part for your car.
How hard the part is to reach on your engine, which sets the labour time.
Whether the engine has already overheated and caused other damage.
This is why catching a leak early usually saves money.
How we can help
We are a mobile mechanic based in Aylesham, so we come to your home or workplace. We cover Canterbury, Dover, Deal, Sandwich, Folkestone and the villages in between. See the full list on our areas we cover page.
We can come out and find where the coolant is going, then tell you what it needs. We replace water pumps ourselves. Labour is £30-£50 per hour depending on the job, parts are extra, and we agree the price with you on WhatsApp before any work starts.
Frequently asked questions
How long can I drive with a coolant leak?
The RAC does not consider it safe to drive on. Avoid long journeys and get it checked as soon as you can, because overheating can wreck an engine.
Why is my coolant going down but there is no leak?
It may be leaking somewhere you cannot see, such as the heater matrix or inside the engine. The AA says white exhaust smoke or milky oil can be signs of a head gasket problem.
Can a coolant leak fix itself?
Do not count on it. The cause needs finding and fixing. The AA says head gasket sealers may work only as a temporary fix and should not be relied on as a long-term repair.
Need help? Send a WhatsApp to 07563 350335 with your car’s make and model and we’ll come to you.
Areas we cover: based in Aylesham, we come to you in Canterbury, Dover, Deal and Walmer, Sandwich and Ash, Folkestone, Wingham, Bridge and Barham, Shepherdswell, and Adisham. See all areas.
Engine problem or belt due?
Message us on WhatsApp with your reg and postcode for a price before any work starts.
WhatsApp for a free quote Call 07563 350335
Labour £30 to £50 per hour depending on the job. Send your reg number and we will reply with a price before any work starts.
