MOT defect file
Brake calliper seized or leaking
Last updated
Quick answer
A calliper is either stuck, so it drags or will not press the pad properly, or it is weeping hydraulic fluid. Both are failures, and a leaking calliper also contaminates the pad next to it.
- Typical cost
- £180–£450
- DIY viability
- Garage job
What you might notice
- The car pulls to one side under braking, or wanders that way even off the brakes
- A hot smell and a wheel noticeably hotter than its opposite number after a short drive
- One pad worn to nothing while the other three still have most of their material
- Fuel consumption that has crept up, plus a car that feels reluctant to roll when you take your foot off
What causes it
- Corroded slider pins or guide bushes, so the calliper cannot move across the disc as the pad wears
- A piston seized in its bore, usually because the dust seal split and let water in
- A collapsed or internally swollen flexible hose holding pressure at the calliper after you lift off
- A handbrake mechanism built into the rear calliper that has rusted solid through lack of use
Advisory or failure?
A calliper that is leaking hydraulic fluid is a major defect. So is one that is insecure, cracked or fractured, and so is a seized piston that prevents the brake operating properly. If the calliper is leaking badly enough that failure looks imminent, the grade becomes dangerous. Separately, a seized calliper almost always shows up on the rollers as a brake imbalance across the axle or as excessive drag, which is itself recorded as a defect, so it is common to see one seized calliper produce two failure entries on the same certificate.
Can you fix it yourself?
Garage job
The mechanical side is within reach of a confident home mechanic — the calliper comes off on two bolts and a hose union — but three things push this one towards a garage. It opens the hydraulic system, so a full, correct bleed is mandatory and a soft pedal afterwards is not something to experiment with on the road. Rear callipers with an integral handbrake need the piston wound in rather than pushed, and doing that wrong destroys the new part. And on any car with an electronic parking brake, the motor has to be retracted with a diagnostic tool first and reset afterwards; force it and you will be buying an actuator as well. If you do tackle it, replace the pads on that side too, because a leaking calliper has almost certainly contaminated them.
What it costs
A remanufactured calliper is typically £70 to £180 for a common car and £250 or more for anything with an electric parking brake motor built in. Fitting plus a bleed is around an hour and a half. Expect £180 to £280 for a straightforward front corner including pads, and £300 to £450 for a rear with an electronic parking brake, because of the diagnostic time either side of the job. The top of the band is where the hose union has seized into a corroded pipe, or where the disc has been overheated and needs replacing at the same time — and since discs are always replaced in pairs, that adds the other side too.
What happens if you ignore it
A dragging brake generates a lot of heat in a small space. It cooks the pad until the friction material glazes and stops working, overheats the disc until it warps and judders, boils the fluid in that corner, and on a rear brake can be enough to damage a wheel bearing. Meanwhile the car is braking unevenly, which means it steers itself under braking — a genuine problem in the wet or on a motorway. Cost-wise this is the classic false economy: caught early it is a calliper and a set of pads, left alone it is a calliper, pads, disc, a fluid flush and sometimes a hub. If the leak reaches the tyre, the fluid attacks the rubber as well.
Common questions
- Is a seized brake calliper an MOT failure?
- Yes. A calliper leaking hydraulic fluid is a major defect, as is one that is insecure, cracked or fractured, or has a piston seized so the brake cannot operate properly. Leaking badly enough that failure looks imminent is dangerous. A seized calliper also shows up on the rollers as imbalance or excessive drag, so one fault often produces two failure items.
- Why does my car pull to one side when I brake?
- Because one brake is doing more of the work. A seized slider or piston either stops that calliper pressing its pad properly, or holds the pad against the disc so it never releases. Either way the effort across the axle is uneven and the car steers itself under braking, which is at its worst in the wet.
- Why is one of my wheels much hotter than the others?
- A calliper that will not release keeps the pad against the disc, so friction generates heat continuously rather than only when you brake. A hot smell and one wheel far hotter than its opposite number after a short drive is the classic sign, usually alongside a car that feels reluctant to roll and uses more fuel than it did.
- Can a seized calliper be freed off rather than replaced?
- Sometimes. Where the problem is corroded slider pins or guide bushes, cleaning and lubricating them along with a new set of pads is a proper repair. A piston seized in its bore, or a calliper weeping fluid past its seals, needs replacing. Fit new pads on that side either way, because a leak has almost certainly contaminated them.
- How much does it cost to replace a brake calliper?
- A remanufactured calliper is typically £70 to £180 for a common car, or £250 and upwards where an electric parking brake motor is built in. Fitting and bleeding is around an hour and a half, so budget £180 to £280 for a straightforward front corner including pads, and £300 to £450 for a rear with an electronic parking brake.
Warning lights behind this
This defect is what a tester writes down. What you see from the driver’s seat is a symbol, and it is worth checking which one, because manufacturers reuse the same shape for more than one system.
This is general guidance, not a diagnosis. The severity DVSA records depends on the specific fault found, so the same item can appear as an advisory on one test and a failure on another. Ask a qualified tester or mechanic to inspect the vehicle.
Has this been recorded on your car?
Check the full MOT history for any UK registration.