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.
Repair cost
Rubbers are inexpensive. Cost only climbs if a bracket has to be fabricated or a section replaced because the hanger has rotted off it.
Before the retest
After exhaust work, start the car from cold and listen for blowing or ticking at the joints, and feel (carefully, before it gets hot) for any section that rattles or hangs low. Every original mounting rubber should be present. A sealed system matters for the emissions part of the test as well, because a leak upstream of a sensor can upset the readings.
Retest rules
If the vehicle stays at the test centre for repair and is retested within 10 working days, a partial retest is often free; some items qualify for a free retest if you bring the car back by the end of the next working day. The exact conditions are set out on GOV.UK, so confirm with the test centre before you leave. A major or dangerous failure means the car cannot legally be driven away unless the previous MOT is still valid and nothing dangerous was recorded — check your certificate first.
Related help
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.