The system isn't properly supported. A missing or perished rubber mount lets the exhaust hang and swing, which then knocks against the underside and puts strain on the joints further forward.
Wording as it commonly appears on an MOT certificate: “Exhaust insecure or a mounting is missing”.
What does it mean?
The system isn't properly supported. A missing or perished rubber mount lets the exhaust hang and swing, which then knocks against the underside and puts strain on the joints further forward.
How serious is it?
Usually recorded as: Major. The tester assesses the actual vehicle on the day, so your certificate is what counts.
What normally causes it?
- Perished rubber mounts — they're a wear item and they harden with heat and age
- A snapped hanger bracket, usually corroded through
- A rusted-out section no longer holding the weight
What a mechanic would check
Grab the tailpipe (cold) and rock the system — a healthy one moves a little and springs back, a loose one swings and touches the floorpan. Then I count the mounts and look for missing or split rubbers.
What might need replacing
- Exhaust mounting rubbers
- A hanger bracket welded or replaced
- A section of exhaust if the hanger has rusted off it
Can you still drive it?
Failure item. Leave it long enough and the swinging exhaust will crack a joint or break something more expensive, so it's worth sorting quickly — mounting rubbers are among the cheapest parts on the car.
More exhaust failures · MOT failure decoder · Ask a mechanic about your certificate
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.