31/12/2000
The annual MOT test is a crucial checkpoint for every vehicle in the UK, ensuring it meets essential roadworthiness and environmental standards. While many components are scrutinised, the humble CV joint is a frequent culprit for failure, often catching vehicle owners by surprise. Understanding why these joints fail and what the consequences are is vital for maintaining your vehicle's safety and ensuring a smooth pass.
Beyond the mechanics, the MOT scheme is a dynamic entity, constantly evolving through updates and directives. These changes are communicated via 'Special Notices', essential memos that keep MOT testers and Approved Examiners (AEs) informed. Grasping the significance of both CV joint integrity and these notices is key to navigating the world of vehicle maintenance and compliance.
Understanding the CV Joint and Its Critical Role
Constant Velocity (CV) joints are integral components of your vehicle's drivetrain, particularly in front-wheel-drive cars, but also found in all-wheel-drive and some rear-wheel-drive vehicles. Their primary function is to transmit power from the gearbox to the wheels at a constant speed, regardless of the angle of the wheel. This allows for the suspension to move up and down, and the wheels to turn left and right, without interrupting the power flow.
Each CV joint is encased in a protective rubber boot, often referred to as a CV boot. This boot serves two crucial purposes: first, it holds the essential lubricating grease within the joint, ensuring smooth operation and preventing wear; second, it acts as a barrier, keeping out contaminants like dirt, water, and grit that would otherwise quickly destroy the intricate internal components of the joint.
Why a CV Joint Fails an MOT
A failed CV joint is a common reason for an MOT refusal, and the cause is almost always linked back to the integrity of its protective boot. Over time, these rubber boots can degrade, crack, or split. This might be due to age, exposure to road debris, or even damage from accidental impacts.
When a CV boot splits, it creates an immediate problem: the vital grease inside the joint begins to escape. As the vehicle moves, the centrifugal force generated by the spinning joint literally flings the grease outwards. Not only does this deprive the joint of its necessary lubrication, leading to rapid and premature wear, but it also poses a significant safety risk.
The escaping grease can spray onto adjacent vehicle components. Critically, if this grease contaminates your vehicle's brake components – such as brake discs, pads, or even callipers – it can severely compromise their effectiveness. Grease on braking surfaces dramatically reduces friction, leading to diminished braking performance and potentially dangerous situations. This direct safety implication is precisely why a split CV boot, even without audible symptoms from the joint itself, constitutes an immediate MOT failure.
Furthermore, once the grease has escaped, dirt, water, and other abrasive contaminants can easily enter the joint. These foreign particles act like sandpaper, grinding down the precision-machined internal components. This accelerated wear leads to slackness in the joint, which can manifest as a characteristic clicking or clunking noise, especially when turning or accelerating. While the MOT primarily fails the boot for grease leakage, a noisy, worn joint will also be noted and lead to a failure.
The Implications of an MOT Failure
If your vehicle fails its MOT due to a CV joint issue (or any other defect), it means your vehicle is not roadworthy and cannot be legally driven on public roads, except to a pre-booked appointment for repairs or a retest. You will receive a 'refusal of an MOT test certificate' document detailing the reasons for failure.
To rectify the issue, the CV boot (and potentially the entire CV joint if significant wear has occurred) must be replaced. Once repairs are completed, the vehicle must undergo a retest. Depending on the type of repair and how quickly it's done, a partial retest might be possible, which is usually cheaper or even free if conducted within a specific timeframe (e.g., within 10 working days at the original test station).
Ignoring a failed CV joint is not an option. Apart from the legal ramifications of driving an unroadworthy vehicle, the safety risks are paramount. A severely worn CV joint can eventually seize or even disintegrate, potentially causing loss of control or leaving you stranded.
Preventative Measures and Maintenance Tips
While CV boots are designed to last, they are subject to wear and tear. Regular visual inspections are your best defence. During routine servicing or even when checking your tyres, take a moment to look at the rubber boots behind your wheels. Look for any cracks, tears, bulges, or signs of grease leakage on the boot itself or on surrounding components like the wheel arch liner or brake lines.
Catching a split boot early can save you money. Replacing just the boot is a much simpler and cheaper job than replacing the entire CV joint, which becomes necessary once the joint itself is worn out due to a lack of lubrication and contamination. If you notice any suspicious noises, particularly a clicking sound when turning, have it investigated by a qualified mechanic immediately. Early diagnosis can prevent a minor repair from escalating into a costly and potentially dangerous breakdown.
| CV Joint Condition | Typical Symptoms | MOT Outcome | Recommended Action |
|---|---|---|---|
| Healthy Boot & Joint | No noise, no grease leakage | Pass | Routine checks |
| Split Boot, Minor Leakage | Grease visible on boot/surroundings, no noise yet | Fail | Replace boot immediately |
| Split Boot, Significant Leakage | Grease on brakes/suspension, possible minor noise | Fail | Replace boot, inspect brakes |
| Worn Joint (due to split boot) | Clicking/clunking noise (especially when turning) | Fail | Replace entire CV joint |
Beyond the technical aspects of vehicle components, the MOT testing scheme itself is governed by a strict set of rules and guidelines that are subject to change. These changes are communicated to MOT testers and Approved Examiners (AEs) through 'Special Notices'. Previously issued by VOSA (Vehicle and Operator Services Agency), these notices are now issued by the Driver and Vehicle Standards Agency (DVSA), which superseded VOSA.
What are MOT Special Notices?
Special Notices are official memos that the DVSA uses to disseminate crucial information, updates, and amendments to the MOT scheme. They cover a wide array of topics, from changes in the MOT Testing Guide and inspection manuals to new equipment requirements, administrative procedures, and even reminders about best practices or disciplinary actions.
These notices are vital for ensuring consistency and compliance across all MOT testing stations in the UK. They ensure that all testers are aware of the latest standards and procedures, which is essential for maintaining the integrity and fairness of the MOT test.
The Importance for MOT Testers and AEs
For MOT testers and AEs, staying up-to-date with Special Notices is not merely good practice; it's a professional obligation. Failure to adhere to the latest directives can lead to incorrect test results, which could have serious implications for vehicle safety or lead to disciplinary action against the testing station or individual tester.
For instance, a notice might introduce a new method for testing emissions, clarify the inspection criteria for specific vehicle types (like quadricycles with hydraulic parking brakes), or even announce changes to administrative processes such as the introduction of plain paper MOT documents. Each notice contributes to the ongoing evolution and refinement of the MOT scheme, aiming for greater efficiency, accuracy, and safety.
Where to Find MOT Special Notices
Accessing the most current and relevant Special Notices can sometimes be a point of confusion for testers. Historically, there have been issues with how these notices are presented and accessed through the MOT Computer system.
As highlighted in the provided information, if you use the MOT Computer to look for Special Notices, you might see a heading like “Current Special Notices”. However, this often only displays notices for the most recent year (e.g., only 2016 notices were shown at one point), leading to the misconception that older, but still valid, notices are no longer relevant. This is a significant point of misinformation.
The correct and comprehensive way to access all Special Notices, regardless of their publication year, is typically through a web browser by navigating to the official DVSA MOT Special Notices page. This page contains a full archive of all notices issued since 1993, though it's important to remember that while all are archived, some older notices relating to transitional periods (like the move to the new MOT Computerisation Service) may no longer be directly relevant to current procedures, even if technically 'current' in the archive.
The DVSA has acknowledged this issue regarding clarity and accessibility and has expressed an intent to clarify the situation. Testers are often advised to consult industry publications and official DVSA communications for the latest guidance on how to view and interpret these notices.
| Source of Notices | Access Method | Content Coverage | Potential Issues |
|---|---|---|---|
| MOT Computer System | Accessed via the MOT testing terminal | Often limited to recent notices (e.g., current year) | May not show all valid or relevant historical notices, leading to incomplete information. |
| DVSA Official Website | Accessed via a web browser (e.g., 'MOT Special Notices' search) | Comprehensive archive of all notices since 1993 | Requires users to filter for relevance; some older notices may be superseded or relate to past transitional phases. |
Frequently Asked Questions About MOTs and CV Joints
- What does it mean if my CV boot is split but the joint isn't making noise?
- Even if the joint isn't making noise, a split boot is an MOT failure. The absence of noise simply means the joint hasn't yet suffered significant wear, but it's only a matter of time. The primary concern for the MOT is the potential for grease to contaminate brake components, which is a significant safety hazard.
- Can I drive my car with a failed CV joint after an MOT?
- No. If your vehicle fails its MOT, it is deemed unroadworthy. You can only drive it to a pre-booked appointment for repairs at a garage, or to a pre-booked MOT retest. Driving it for any other purpose is illegal and could lead to fines, points on your licence, or invalidate your insurance.
- How much does it typically cost to repair a CV joint or boot?
- The cost varies significantly. Replacing just a CV boot is considerably cheaper, often ranging from £50-£150, including labour. Replacing the entire CV joint is more involved and can range from £150 to £400 or more, depending on the vehicle make and model, and whether an inner or outer joint needs replacing. Early detection of a split boot can save you money.
- How often should I check my CV boots?
- It's a good practice to visually inspect your CV boots at least twice a year, perhaps during your seasonal tyre checks or oil changes. Any time your vehicle is raised for maintenance is an opportune moment. Look for cracks, tears, or signs of grease leakage around the inner and outer CV joints.
- Who issues MOT Special Notices?
- MOT Special Notices are issued by the Driver and Vehicle Standards Agency (DVSA), which is the executive agency of the UK Department for Transport responsible for carrying out driving tests, approving people to be driving instructors and MOT testers, and carrying out tests to ensure lorries and buses are safe to drive, among other functions.
- Are all Special Notices on the DVSA website still relevant?
- While the DVSA website hosts an archive of all Special Notices, not all older notices may be directly relevant to current testing procedures. Some might relate to transitional phases or historical changes that have since been superseded. Testers are expected to use their professional judgment and cross-reference with the latest version of the MOT Testing Guide and other current DVSA publications.
In conclusion, a failing CV joint, primarily due to a split boot and escaping grease, is a direct route to an MOT failure, posing significant safety risks. Regular inspection and prompt repair are essential. Simultaneously, for those involved in the MOT scheme, understanding and accessing the timely updates provided by DVSA Special Notices is paramount. Both aspects underscore the commitment to road safety and the continuous effort to maintain high standards within the UK's vehicle fleet.
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