MOT advisory: rigid brake pipe corroded
The metal pipes that carry brake fluid run along the underside of the car, where road salt and water reach them. Surface rust on them is common on older cars. The tester saw corrosion, or a coating of grease or dirt, but didn't think the pipe was weakened enough to fail.
What the tester wrote
| Result | Wording on the certificate | Category |
|---|---|---|
| Advisory | Rigid brake pipes: corroded, covered in grease or other material | Advisory (pass) |
| Fail | Rigid brake pipes: excessively corroded | Major |
What the MOT checks
Testers look along the pipes from underneath, and a pipe that's excessively corroded fails. The manual admits that judging how much metal is left is hard, and tells testers to give the benefit of the doubt when they're not sure.
So this advisory covers a wide range, from a light coat of surface rust to pipes that are close to the line.
"Chafing, corrosion or damage to a rigid brake pipe so that its wall thickness is reduced by 1/3 (approximately 0.25mm for typical hydraulic brake pipe) justifies rejection, although it’s accepted that this is not easy to determine."
MOT inspection manual, section 1.1.11 Rigid brake pipes. Read it on GOV.UK
How common it is
In 2025 this advisory was recorded on 3.7 in every 100 class 4 MOT tests (1,222,471 of 33,210,774 initial tests). The matching fail was recorded on 0.5 in every 100 (172,590 tests).
The typical car with the advisory was 15 years old with 98,269 miles recorded (medians).
| Age at test (years) | Advisory per 100 tests | Fail per 100 tests |
|---|---|---|
| 0-2 | not shown | not shown |
| 3 | not shown | not shown |
| 4-5 | 0.2 | not shown |
| 6-7 | 0.8 | 0.1 |
| 8-10 | 2.1 | 0.3 |
| 11-14 | 4.7 | 0.7 |
| 15-19 | 8.9 | 1.3 |
| 20+ | 14.2 | 1.9 |
'Not shown' means fewer than 1,000 tests in that cell, or a cell hidden so a small one can't be worked out. Age is years since first registration. First MOTs often happen just before a car's third birthday, so many show as age 2.
Does it turn into a fail at the next MOT?
We followed the same cars to their next MOT, 240 to 500 days later (981,100 pairs where this advisory was recorded). 7.0% failed on the same item at that next test, and another 47.4% had the same advisory again.
Among cars where this item wasn't noted at all, 0.29% failed on it next time. So a car with this advisory was about 24 times as likely to fail on this item as one without it.
These are averages. We can't see what owners did between tests. Some will have fixed the problem, and a fix would stop a fail.
What it usually means for a buyer
Of the pilot advisories, this is one of the more likely to turn into a fail on the same item. That makes sense, because corrosion only goes one way.
On a car with this note, ask whether the pipes have been replaced since, and look underneath if you can. Flaking, swollen or crusty pipes are a reason to get a garage to look before you agree a price. This note is very rare on young cars, so seeing it on a newer car is unusual.
Typical fix
Corroded sections are replaced with new pipe, often copper-nickel, which resists rust, and the brakes are bled afterwards. It's skilled work on a safety system, so leave it to a garage. Prices vary a lot by car and garage, so get a quote for the specific car.
Questions to ask the seller
You can read any car's MOT history, including advisories, free on GOV.UK. Our MOT advisory decoder explains the other notes in plain English.
Related MOT advisories
- Sub-frame corroded but not seriously weakened
- Brake pad wearing thin
- All MOT defects
- Buying a used car: a step-by-step guide
Sources and limitations
- Data: DVSA MOT anonymised test results and test items, class 4 initial tests, 2024 and 2025 (open data on GOV.UK). Same DVSA data as our MOT dataset.
- 'Fail' includes items fixed at the test centre within an hour (pass after rectification).
- An advisory is a tester's judgement on the day. Testers differ, and some problems are not visible at an MOT.
- The MOT is not a service and does not check the engine, clutch or gearbox in depth.
- Counts under 1,000 are not shown. No make or model figures are published here.
Contains public sector information licensed under the Open Government Licence v3.0. Source: Driver and Vehicle Standards Agency (DVSA), MOT Anonymised Data. Analysis by CarCheckHQ. Not endorsed by DVSA.
Written by the CarCheckHQ team.