MOT advisory “Sound deadening material not fully secure” — meaning and what to do

This advisory means the tester found sound deadening material that is not fully secure — not bad enough to fail, but expected to need attention before your next MOT. It was recorded 5,061 times on UK certificates in 2025, making it one of the most common advisories in the country.
5,061Times recorded in 2025
Noise, emissions and leaksVehicle system
AdvisoryDoes not fail the test

What the tester saw

MOT testers work from the DVSA inspection manual. For this item the manual wording is “Any part of the noise suppression system insecure”. In plain English: there is wear or deterioration on the sound deadening material that is currently within legal limits (defect category: Major). The tester is flagging it so you can plan the repair before it becomes a fail — or a roadside problem.

Do you need to fix it?

Not to stay legal today — an advisory does not affect the pass. But advisories are the tester telling you what will likely fail next time. Two sensible rules:

  • Safety-critical systems first. Noise, emissions and leaks advisories are usually less urgent, but get a quote now so the cost doesn’t surprise you later.
  • Buying a used car? Repeated advisories for the same item across several years of MOT history mean the owner has been ignoring it. Check the car’s full record with our free MOT history check.

Typical repair cost

A minor leak traced and fixed early is often £50–£150. Left alone, exhaust sections run £150–£400 and catalytic converters far more.

DIY check before the garage visit

Rule out related electronic faults yourself — a scan takes two minutes and saves a diagnostic fee.

Related noise, emissions and leaks advisories

Engine oil leaks leak, but not excessive2,411,665 recorded in 2025 Transmission oil leaks leak, but not excessive329,757 recorded in 2025 Other leaks leak, but not excessive40,100 recorded in 2025 Undertray not fully secure24,718 recorded in 2025 Hydraulic fluid leaks leak, but not excessive11,934 recorded in 2025 Catalyst emissions emits blue smoke during...10,484 recorded in 2025

FAQs

Will “not fully secure” fail my next MOT?

Not automatically — it fails only when the wear crosses the legal threshold in the inspection manual. But this advisory is the most common precursor: if left unattended, expect it to become a Minor or Major defect at a future test.

Can I ask the garage to remove an advisory?

No. Advisories are part of the official test record held by DVSA and appear in the vehicle’s public MOT history. Fixing the item means it simply won’t be advised next time.

Does an advisory affect the car’s value?

Slightly, yes — buyers who check MOT history (which is free) will price in the pending repair. Fixing cheap advisories before selling usually pays for itself.

Frequency: DVSA anonymised MOT data, 2025 (Class 4). Wording follows the DVSA inspection manual. Contains public sector information licensed under OGL v3.0.