Topping up coolant regularly with no puddle on the driveway is one of the more worrying symptoms, because it often means the coolant is going somewhere it should not. Here is where to look.
Small external leaks that evaporate
A tiny leak from a hose clamp or the water pump can seep and evaporate on a hot engine before it drips, leaving only a faint crusty residue. Check hoses, clamps and the pump area for staining.
A failing radiator cap
A weak cap lets the system lose pressure and vent coolant as vapour when it gets hot. It is a cheap part to replace and a common cause of slow, mysterious loss.
Internal leaks
More seriously, a failing head gasket can let coolant burn in the cylinders, showing as sweet smelling white smoke from the exhaust, or leak into the oil, turning it milky. This one needs prompt attention.
What to check first
Look for external staining, replace a tired cap, and check the exhaust for white smoke and the oil for a milky look. Those three checks point you toward the cause.
Frequently asked questions
Is it safe to keep driving?
Only while you top up and watch the temperature. Overheating from low coolant can cause serious damage, so do not ignore it.
Can a bad cap really cause coolant loss?
Yes. A cap that will not hold pressure vents coolant as vapour and is an easy first fix.
Keep your cooling system healthy with the right fluids from our engine and fluid guides.
