The underside of a vehicle can reveal issues that aren’t visible during everyday driving. MOT testers carefully inspect this area because it directly affects roadworthiness and safety. Hidden rust, leaks, or damage underneath could lead to dangerous failures if left unchecked.

Suspension and Steering Components

One of the first areas MOT testers examine is the suspension system. They check for:

• Worn or damaged shock absorbers
• Loose or corroded suspension arms
• Excessive play in steering joints or linkages

Any weakness here can affect stability, especially when braking or cornering.

Brake Lines and Hoses

The brake system is a critical safety element. Testers inspect:

• Hydraulic brake pipes for corrosion, leaks, or damage
• Flexi-hoses for cracks or wear
• Secure mounting and correct routing of pipes

Even minor leaks can cause an MOT failure, as brakes must perform consistently under pressure.

Exhaust System and Emissions

The exhaust runs the full length of the car, so much of it is only visible from underneath. MOT testers look for:

• Leaks or holes in the exhaust pipes
• Secure mounting and hangers
• Excessive noise caused by damage
• Emissions compliance during testing

A leaking exhaust not only increases pollution but can also pose a danger to occupants if fumes enter the cabin.

Fuel System Checks

Fuel tanks, pipes, and connections are inspected for leaks or corrosion. Any sign of fuel escaping is an immediate MOT failure. Testers also ensure pipes are properly secured and not rubbing against moving parts.

Rust and Corrosion on the Chassis

Rust is one of the biggest threats to vehicle safety. Testers check:

• Chassis rails and sills for structural corrosion
• Mounting points for suspension, brakes, and seatbelts
• Excessive rust within 30cm of a safety-critical component

Surface rust is usually acceptable, but significant corrosion can fail the MOT.

Oil and Fluid Leaks

Excessive fluid leaks from the engine, gearbox, or differential are flagged during an MOT. Testers look for drips that could pose fire risks or affect road safety.

Conclusion

When MOT testers look under a car, they are ensuring every hidden component is safe and secure. From brakes to rust checks, these inspections are vital for spotting issues before they become serious hazards.

Regular servicing and underbody inspections between MOTs can help avoid unexpected failures.

FAQs

1. Do MOT testers always check under the car?

Yes, the underside inspection is a standard part of every MOT test.

2. Will minor rust fail an MOT?

Minor surface rust won’t, but structural corrosion near key components will.

3. Can an exhaust leak cause MOT failure?

Yes, exhaust leaks, excessive noise, or high emissions can all result in a fail.

4. Do fluid leaks automatically fail an MOT?

Significant leaks usually cause failure, while minor dampness may be noted as an advisory.