Reliability and common problems
Recurring MOT Advisories: Which Faults Should Stop You Buying?
An advisory notice on a single MOT test is normal wear. But when the same warning repeats across two, three, or four consecutive years, it exposes chronic maintenance neglect. Here is which recurring faults should make you walk away.
TL;DR: Recurring advisories summary
Advisories vs major defects explained
During an official MOT test, licensed DVSA testers categorise vehicle conditions into three distinct tiers:
- Dangerous: Constitutes an immediate, severe risk to road safety or the environment. The vehicle fails instantly and cannot be driven on public roads.
- Major: May affect safety, put other road users at risk, or exceed emissions limits. Results in an immediate failure that must be repaired.
- Minor / Advisory: No immediate risk to safety, but indicates a component is approaching wear limits or showing early signs of deterioration. The car passes, but the note is recorded permanently on government records.
Because advisories do not prevent the car from passing, negligent vehicle owners frequently ignore them for years, passing the accumulated repair burden directly onto the next unsuspecting buyer.
The 5 high-risk recurring fault categories
Not all repeat advisories carry equal financial or safety risk. Consumables like tyre edge wear or wiper blades are cheap to replace. However, the five categories below represent serious underlying mechanical or structural problems:
1. Structural and subframe corrosion
Advisories containing terms such as corrosion, subframe corroded, chassis mounting, or sill corroded close to prescribed area are critical warnings. While surface rust is common on UK underbodies due to winter road salt, rust near suspension mountings or seatbelt anchorages weakens vehicle structural rigidity. Once corrosion reaches prescribed safety areas, welding and structural subframe replacements can cost £1,000 to £2,500.
2. Fluid and oil leaks
Phrases like oil leak, coolant leak, antifreeze leak, or fluid leak indicating oil or fluids dripping onto hot exhaust pipes, steering racks, or undertrays signal failing gaskets, degraded hoses, or split steering gaiters. A small seep can quickly develop into catastrophic engine oil starvation or sudden power steering failure.
3. Brake system and hydraulic lines
Notices mentioning brake pipe corroded, brake fluid leak, or brake disc worn close to limit that recur across multiple MOTs reveal reckless brake maintenance. Corroded rigid brake lines can rupture under heavy emergency braking, causing immediate total loss of hydraulic brake pressure.
4. Suspension bushes and mounting play
Advisories noting suspension arm pin or bush worn but not resulting in excessive movement or shock absorber weeping mean suspension geometry is degraded. Leaving worn bushes unreplaced accelerates uneven tyre wear, causes steering drift, and strains neighbouring suspension ball joints.
5. Emissions, smoke and exhaust leaks
Recurring notes mentioning exhaust gas leak, emissions close to limit, smoke opacity, or lambda reading indicate faulty catalytic converters, failing diesel particulate filters (DPFs), or malfunctioning lambda sensors. Replacing a blocked DPF or catalytic converter on modern Euro 6 cars often costs £800 to £2,000.
Why mileage context matters with repeat notes
Interpreting repeat MOT notes requires cross-referencing with odometer readings between each test:
Estimated repair costs for recurring faults
Here is what recurring MOT advisory warnings typically cost to rectify in UK workshops:
Typical Workshop Repair Costs for Recurring MOT Advisories
| Advisory Type | Typical Keyword Warning | Required Rectification | Typical UK Cost |
|---|---|---|---|
| Subframe / Chassis Rust | Corrosion / structural mounting | Welding plate fabrication or full subframe replacement | £600 to £2,200 |
| Engine Oil Leak | Oil leak / fluid leak | Rocker cover, sump gasket, or crankshaft rear main seal | £250 to £950 |
| Brake Hydraulic Lines | Brake pipe corroded / ferrule rust | Flaring and replacing copper/nickel brake lines | £180 to £450 |
| Suspension Bushes | Bush worn / suspension play | Control arm replacement and 4-wheel alignment | £200 to £600 |
| DPF / Exhaust Leak | Exhaust gas / emissions lambda | DPF chemical cleaning, sensor swap, or new catalytic converter | £400 to £1,800 |
How to negotiate or walk away safely
Before committing to buy any used car with recurring advisory notices:
- Review the history online: Enter the registration in the Caroat MOT check to see all past advisories and tester comments across every test since 2005.
- Ask for fresh proof: Demand recent workshop invoices proving the recurring advisory item was physically resolved with new parts rather than ignored.
- Deduct full repair estimates: If the advisory is still active, obtain a written quote from an independent garage and deduct that exact amount from the seller's asking price.
- Walk away from structural rust: Never compromise on severe underbody, subframe, or chassis corrosion unless you are a professional welder or restorer.
Check any vehicle's recurring MOT advisories
Sources
- MOT inspection manual for cars and passenger vehiclesDriver and Vehicle Standards Agency (DVSA)
- Vehicle safety standards and defect categoriesGOV.UK
FAQ
What is the difference between an MOT defect and an MOT advisory?
A defect (dangerous or major) causes an immediate MOT test failure and must be repaired before a vehicle can pass. An advisory notice is a warning from the tester indicating that a component is showing wear or minor deterioration and will require monitoring or repair in the near future.
Why are recurring MOT advisories a major red flag for used car buyers?
When the same advisory notice appears year after year across multiple MOT tests, it proves the previous owner deferred routine maintenance and ignored garage warnings. Repeated corrosion, brake wear, or oil leak advisories often escalate into dangerous and costly catastrophic failures.
Which recurring MOT advisories should make you walk away from a car?
Structural corrosion within 30cm of safety mounts, severe subframe rust, persistent brake hydraulic leaks, heavy oil leaks onto exhaust or steering components, and recurring emissions warnings should generally prompt you to walk away or demand substantial price reductions to cover major repairs.
How does mileage affect the significance of recurring MOT notes?
An advisory that repeats over 3,000 miles in two years shows the car sat idle while rusting or degrading. An advisory repeating over 25,000 miles of heavy use means the component has experienced extreme sustained wear and is likely on the verge of total failure.
How can I check all historical MOT advisories for a UK car?
You can enter the car's registration into Caroat to view the full official DVSA MOT history, including every historical pass, failure reason, and advisory item dating back to 2005.