Soft pedal, or fluid near a wheel? Don't drive it
If the pedal feels soft or spongy, sinks towards the floor, or there's wet fluid around a wheel, leave the car where it is and arrange a tow or a mobile mechanic. If the brakes fade while you're moving, RACV says to stay calm, pump the pedal several times to build pressure and slow gradually. Don't swing the wheel or snatch the handbrake. Ease it on slowly, once you've shed what speed you can. If anyone is hurt or in danger, call 000.
Why can't you just top it up?
Press the pedal and fluid pushes the pads onto the discs. A leak lets that pressure escape, and RAC WA warns that if the reservoir runs empty, air can get in and dangerously compromise braking.
A top-up refills the tank and leaves the hole. NRMA says a level that's low or falling quickly could mean a leak that could lead to brake failure. The fix is the failed part, then fresh fluid, then bleeding out the air.
Is it definitely a leak?
Not every low level is one. RAA says pad wear slowly lowers the fluid, which usually isn't a concern and gets looked at during a service. A sudden drop or an empty reservoir is different: RAA calls that a serious problem, most likely a leak.
To find the reservoir, look towards the back of the engine bay, usually on the driver's side. It's a see-through plastic tank with maximum and minimum marks. Read it on flat ground with the engine off, and leave the cap on.
What's that fluid under the car?
| What you'll notice | Where it usually shows | |
|---|---|---|
| Brake fluid | A strong, pungent smell, sometimes before you can see anything, RAA says | Around a wheel, or along a brake line |
| Engine oil | Black, with a burning smell | Under the engine. See oil leaks |
| Coolant | Green or orange, with a sweet smell after a run | Near the hoses or radiator. See coolant leaks |
| Transmission fluid | Generally bright red | A trail under the car. See transmission fluid leaks |
| Clear water | Just water | Condensation from the air conditioner, and nothing to worry about |
Where do brake fluid leaks start?
- Brake hoses: the flexible lines near each wheel, which can perish with age or rub through.
- Disc calipers: the clamps that squeeze the pads. Their piston seals can weep.
- Wheel cylinders: small pistons inside rear drum brakes. A leak here can stay hidden inside the drum.
- Master cylinder: the part under the reservoir that turns pedal pressure into fluid pressure. When it fails inside there may be no puddle, only a pedal that slowly sinks.
- Steel brake lines: the pipes running along the underbody, which rust over time, more so on cars that see salt water.
RAA says modern parts make these leaks uncommon, and that they turn up mostly on older or heavily used cars. On a manual with a hydraulic clutch, the clutch uses the same fluid, so the mechanic should check that side as well.
What does the mechanic do to fix it?
They'll raise the car, take the wheels off (and the drums, if it has them) and trace the wet trail back to where it starts. Then they replace the failed part, refill with the fluid your owner's manual lists and bleed each brake until no air comes out. A good mechanic tests the pedal before you get the keys back.
Any mechanic who does regular brake work can handle this. Ask what else the leak has touched: fluid on a pad or shoe can spoil it, so those may need replacing too.
What makes the job bigger or smaller?
One perished hose is a small job. A rusted line that runs the length of the car takes longer, and a master cylinder is bigger again. Pads or shoes soaked in fluid add to the list.
Fresh fluid usually comes into it. RAA says brake fluid should generally be replaced every two to three years because it absorbs moisture, and NRMA says it can take on about 2% in a year. That matters because moisture lowers its boiling point, and fluid can pass 200°C under heavy braking.
Ask for a written estimate that names the failed part, anything else it damaged, and whether the old fluid is being flushed out.
What's safe for you to do, and what isn't
You can
- Read the reservoir level with the engine off, on flat ground.
- Note where the fluid is, and take a photo.
- Keep kids and pets away from a spill. RAC WA says brake fluid is highly toxic and tastes sweet.
- Rinse any off your paintwork straight away, because it strips paint.
Leave to the mechanic
- Finding the leak and replacing the failed part.
- Bleeding the air out of the brakes.
- Checking pads, shoes and discs for contamination.
- Testing the brakes before the car goes back on the road.
Where we'd start
Keys out, car parked. If the level's under the minimum line or the pedal feels wrong, we wouldn't drive it to the mechanic, even if the workshop is close. We'd send the job, say the fluid's low, and ask for someone who can come to the car or have it towed in. Brakes are the one system where a short trip isn't a small risk. Once the leak's found it's usually a straightforward repair, so it's a good one to get done early.