A rigid brake pipe has corroded to the point where the tester judged its strength compromised. There's a real difference between surface rust, which is normal on an older car, and flaking corrosion that's eating into the wall of the pipe — this wording means the latter.
Wording as it commonly appears on an MOT certificate: “Brake pipe excessively corroded”.
What does it mean?
A rigid brake pipe has corroded to the point where the tester judged its strength compromised. There's a real difference between surface rust, which is normal on an older car, and flaking corrosion that's eating into the wall of the pipe — this wording means the latter.
How serious is it?
Usually recorded as: Major, Dangerous. The tester assesses the actual vehicle on the day, so your certificate is what counts.
What normally causes it?
- Age and road salt, particularly on cars used on gritted Scottish roads through winter
- Pipes routed against a chassis rail where dirt packs in and holds moisture
- Stone damage stripping the protective coating years earlier
What a mechanic would check
Get the car up and follow the pipe run end to end, paying attention to where it clips to the body and where it passes over the rear axle. I'd scrape gently at the worst patch — if the corrosion flakes away and leaves a pitted pipe, it's going to be replaced, not cleaned up.
What might need replacing
- The affected pipe section replaced, usually made up and flared to length
- In bad cases, a full set of pipes on an older car
Can you still drive it?
This can be recorded as Dangerous, and rightly so — a corroded pipe can let go under hard braking with no warning at all, and you lose a circuit instantly. Don't drive it and don't put off the repair.
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This is general guidance from a UK mechanic, not a substitute for a physical inspection. Only the tester who inspected your vehicle can confirm what was recorded and why.