Bonnet Struts & MOT Boot Rules: A UK Guide

In the intricate world of vehicle maintenance, some components often go unnoticed until they cease to function correctly. From the humble bonnet strut that tirelessly holds your bonnet aloft to the critical function of your boot lid, understanding these elements is vital for both your vehicle's safety and its ability to pass the annual MOT test. This guide will delve into the specifics of bonnet struts, their function, and the often-misunderstood rules surrounding boot access during an MOT inspection, particularly addressing scenarios where external access might be compromised.

The Unsung Heroes: What Exactly Does a Bonnet Strut Do?

When you pop your bonnet to check the oil, top up the screenwash, or tackle a DIY repair, you likely take for granted the mechanism that keeps that heavy metal lid securely open. That mechanism is often a bonnet strut, a marvel of simple engineering that plays a crucial role in vehicle maintenance and safety.

Function and Mechanics of a Bonnet Strut

At its core, a bonnet strut is a gas-filled cylinder, often referred to as a gas strut or gas spring. It comprises a sealed cylinder containing pressurised inert gas (typically nitrogen) and a small amount of oil, through which a piston rod moves. When the bonnet is opened, the gas pressure inside the cylinder extends the piston rod, effectively pushing the bonnet upwards and holding it in place. This counteracts the weight of the bonnet, making it feel lighter and preventing it from crashing down unexpectedly. In older vehicles, or some current models, a simple prop rod might be used, but gas struts offer superior convenience and safety.

The primary functions of a bonnet strut include:

• Support: Holding the bonnet securely in the open position, allowing unobstructed access to the engine bay.
• Ease of Use: Making the act of opening and closing the bonnet a smooth, controlled, and relatively effortless task.
• Safety: Preventing the bonnet from falling unexpectedly, which could cause serious injury to anyone working beneath it. This is particularly important when performing routine checks or more extensive repairs, ensuring engine bay safety.

Signs of a Failing Bonnet Strut

Like all mechanical components, bonnet struts are subject to wear and tear. Over time, the gas can leak, or the seals can degrade, leading to a loss of pressure. Recognising the signs of a failing strut is important:

• Bonnet Sagging or Falling: The most obvious sign is if the bonnet struggles to stay open or drops down on its own.
• Difficulty Lifting: If the bonnet feels unusually heavy to lift, the struts are likely losing their assistive power.
• Squeaking or Grinding Noises: While less common, worn components within the strut can sometimes produce audible complaints.
• Visible Leaks: Although rare, a damaged seal might allow oil to seep out, indicating a significant failure.

Ignoring a failing bonnet strut isn't just an inconvenience; it's a safety hazard. A sudden drop of the bonnet can cause severe head or hand injuries, making timely replacement crucial.

Replacement and Maintenance

Replacing bonnet struts is often a straightforward task for a competent DIY enthusiast, typically involving unbolting or un-clipping the old units and fitting new ones. However, due to the weight of the bonnet and the potential for injury, it's always advisable to have a second person assist or to use a sturdy prop to secure the bonnet during the process. If you're unsure, a professional mechanic can perform the replacement quickly and safely. Generally, bonnet struts require minimal maintenance beyond ensuring their mounting points are free from corrosion and their operation is smooth.

Beyond Storage: Understanding Your Boot & The MOT Test

While the bonnet strut is about accessing the front of your car, the boot lid is about the rear. And when it comes to the MOT test, the functionality of your boot is under scrutiny, often leading to confusion and, at times, frustration for vehicle owners.

Why Boot Access Matters for an MOT

The boot, or luggage compartment, is not just a space for your shopping or spare tyre. During an MOT inspection, the examiner needs access to this area for several critical reasons:

• Structural Inspection: To check the rear floor, wheel arches, and chassis for corrosion, damage, or inadequate repairs.
• Security of Components: To ensure that items like the spare wheel (if present), battery (if located in the boot), and other fixtures are securely fastened.
• Lighting and Wiring: To inspect the wiring for rear lights, number plate lights, and any tow bar electrics.
• Seatbelt Anchorages: If the vehicle has rear seats, especially in an estate or hatchback, the seatbelt anchorages are often accessible or visible from the boot area.
• General Condition: To ensure there are no dangerous items, sharp edges, or unauthorised modifications within the compartment.

Essentially, the examiner needs to confirm the vehicle's structural integrity and safety features are up to standard, and full access to the boot is paramount for this.

Is a Non-Opening Boot a Reason for Rejection (MOT)?

This is a common query, and the answer, based on the official DVSA (Driver and Vehicle Standards Agency) MOT inspection manual, is generally a resounding 'yes' if the primary external opening mechanism is defective.

The MOT manual for Class 3, 4, 5, and 7 vehicles (which covers most cars) in Section 6.2 (Body and Fittings) clearly states: "Tailgate/boot lid, rear doors, side doors, and sliding doors must: be capable of being opened and securely latched."

This wording is crucial. It implies that the boot lid must operate as intended by its design. If the external latch mechanism is broken, jammed, or otherwise inoperable, preventing the boot lid from being opened using its primary method, it constitutes a defect.

Addressing the 'Internal Access' Argument

Some vehicle owners, like 'wonkyone' in the provided scenario, might argue that if the boot's contents are accessible by folding down the rear seats, this should suffice. While it's true that accessing the contents might be possible this way, it does not negate the requirement for the boot lid itself to be "capable of being opened and securely latched" via its intended mechanism.

An MOT inspector needs to physically open the boot lid to inspect the hinges, the latch mechanism itself, the surrounding bodywork for corrosion, and the integrity of the lid's attachment to the vehicle. If the external latch is broken, they cannot perform these checks adequately. Therefore, the ability to access the *inside* of the boot by folding seats is typically not an acceptable substitute for a properly functioning external boot lid opening mechanism.

A broken external boot latch will almost certainly lead to an MOT Failure. The inspector isn't just checking if you can get your groceries out; they're checking the safety and structural integrity of the entire boot assembly.

Scenarios and Implications

• Broken External Latch: If the button, handle, or remote release for the boot lid does not work, it will be a major defect.
• Jammed Shut: A boot that is permanently jammed shut and cannot be opened at all, even after attempted repair, is a clear failure.
• Insecure Latch: Conversely, a boot that doesn't latch securely (i.e., it can pop open unintentionally) is also a failure, as it poses a safety risk of items falling out or the lid obstructing vision.

The comment about "welding it shut" humorously highlights the desperation some owners feel, but it underscores the point: the boot needs to be functional and safe. Proper repair of the latch or mechanism is the only way to ensure compliance and safety.

What About Different Boot Types?

The principle applies universally, whether you have a hatchback, saloon, or estate car:

• Hatchbacks and Estates: The entire rear door (tailgate) must open and latch securely.
• Saloons: The boot lid, separate from the rear window, must open and latch securely. Some older saloons might only have an internal or remote release, which must still function.

If your vehicle is designed without an external boot release (e.g., some saloon cars where the boot is only accessible via an internal lever or remote fob), then that internal/remote mechanism must function correctly. However, if an external mechanism is present and designed to be used, it must work.

Comparing Functional vs. Faulty Components

To summarise the importance of these components, consider the direct impact of their functionality:

Frequently Asked Questions (FAQs)

Q1: Can I drive with a broken bonnet strut?

A1: While there's no specific law against driving with a broken bonnet strut, it's highly inadvisable. If you need to access your engine bay, you risk injury. Furthermore, if the bonnet latch itself were to fail at speed, a bonnet that's not properly supported could fly open, obstructing your view and causing a serious accident. Always get it repaired promptly.

Q2: How much does it cost to replace bonnet struts?

A2: The cost can vary significantly depending on your car's make and model, and whether you do it yourself or have a garage do it. Parts can range from £20-£100 per pair, with labour adding another £30-£80. It's generally a relatively inexpensive repair for the safety and convenience it provides.

Q3: Is an internal boot release sufficient for an MOT if the external one is broken?

A3: Generally, no. The MOT test requires the boot lid to be "capable of being opened and securely latched" via its intended mechanism. If the external release is broken, even if you can access the boot by folding down seats or using an internal lever, the primary external function is defective, which is typically an MOT failure. The inspector needs to check the external components of the lid and latch.

Q4: What if my car's remote boot release fails, but the manual key release still works?

A4: If there is a manual key release or an internal lever that still allows the boot to be opened and securely latched, then it should generally pass the MOT, as the boot is still "capable of being opened." The failure of a convenience feature like a remote fob might not be an MOT failure in itself, as long as a primary, functional method of opening exists.

Q5: Are there any exceptions for a non-opening boot during an MOT?

A5: Exceptions are extremely rare. The only scenario would be if the vehicle was *designed* without a conventional opening boot lid (e.g., some very specific custom vehicles or modifications that are permanently sealed from the factory, which is highly uncommon for standard production cars). For any standard car with a boot lid designed to open, it must function correctly for the MOT.

Conclusion

Both bonnet struts and boot lid mechanisms, while seemingly minor, are crucial for the safe and compliant operation of your vehicle. A functioning bonnet strut ensures safe access to your engine, preventing potential injuries, while a correctly operating boot lid is non-negotiable for passing your MOT and ensuring the overall safety and structural integrity of your car's rear section. Don't leave these components to chance; proactive maintenance and prompt repairs are key to keeping your vehicle safe, roadworthy, and compliant with UK regulations. If in doubt about any aspect of your vehicle's functionality, always consult a qualified mechanic.

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