Common MOT Failures and How We Fix Them - Car-Pol Gloucester

Every year, around 40% of vehicles in the UK fail their MOT test. At Car-Pol Auto Services in Gloucester, we see hundreds of MOT failure reports and have become experts at quickly diagnosing and repairing the issues that cause vehicles to fail. In this comprehensive guide, we'll explain the most common MOT failures and exactly how we fix them.

Important: Our Service Focus

Car-Pol Auto Services specializes in MOT failure repairs, not MOT testing. We are not an MOT testing station. When your vehicle fails its MOT at an official testing station, bring us the failure report (VT30), and we'll carry out professional repairs to get your vehicle ready to pass the retest.

The 7 Most Common MOT Failure Categories

Based on official DVSA statistics and our own experience, here are the seven most common categories of MOT failures, listed in order of frequency:

1. Lighting and Signaling Failures (30% of all failures)

Lighting issues are the single most common reason vehicles fail MOT tests. The good news is that most lighting problems are quick and inexpensive to fix.

Common Lighting Failures:

Blown Bulbs:
Headlight bulbs, tail light bulbs, brake light bulbs, indicator bulbs, number plate lights, and fog lights can all fail. Sometimes bulbs blow just before the MOT test, and the driver doesn't notice.

How We Fix It: We replace all faulty bulbs with high-quality replacements. For most vehicles, this takes 15-30 minutes. We always check all lights after replacement to ensure they're working correctly.

Headlight Aim:
Headlights must be aimed correctly - not too high (dazzling oncoming traffic) or too low (inadequate road illumination). Misaligned headlights are a common failure point.

How We Fix It: We use professional headlight alignment equipment to adjust the beam pattern to manufacturer specifications. This ensures your headlights provide optimal visibility without dazzling other drivers.

Damaged Light Units:
Cracked lenses, broken reflectors, or water ingress in light units will cause MOT failure. Even small cracks can be enough to fail.

How We Fix It: We replace damaged light units with new or high-quality used units. For some vehicles, we can source individual lenses rather than replacing the entire unit, saving you money.

Indicator Function:
Indicators must flash at the correct rate (60-120 flashes per minute). Too fast or too slow indicates a fault, usually a failed bulb or faulty flasher relay.

How We Fix It: We diagnose the cause (usually a blown bulb or faulty relay) and replace the faulty component. We verify the flash rate meets MOT requirements.

Typical Cost: £20-£150 depending on the specific issue and vehicle model.

2. Suspension Failures (20% of all failures)

Suspension problems are the second most common MOT failure. Suspension issues can be more complex and expensive to fix than lighting problems, but they're crucial for vehicle safety.

Common Suspension Failures:

Worn Shock Absorbers:
Shock absorbers (dampers) wear gradually over time. Leaking fluid, excessive bouncing, or poor damping will cause failure.

How We Fix It: We replace worn shock absorbers in pairs (both fronts or both rears) to maintain balanced handling. We use quality replacement parts from reputable manufacturers. After fitting, we test drive the vehicle to verify improved handling and ride quality.

Broken or Weak Springs:
Coil springs can break or weaken, causing the vehicle to sit lower on one side or provide inadequate suspension travel.

How We Fix It: We replace broken or weak springs, again in pairs to maintain vehicle balance. For vehicles with adjustable ride height, we set the correct height according to manufacturer specifications.

Worn Ball Joints:
Ball joints connect suspension components and allow movement. Excessive wear causes play in the suspension, affecting handling and safety.

How We Fix It: We replace worn ball joints and carry out wheel alignment to ensure proper tracking. This prevents uneven tyre wear and ensures stable, predictable handling.

Worn Track Rod Ends:
Track rod ends (tie rod ends) connect the steering system to the wheels. Wear here causes play in the steering and affects wheel alignment.

How We Fix It: We replace worn track rod ends and perform four-wheel alignment. This ensures your steering is responsive and your tyres wear evenly.

Perished Bushes:
Rubber bushes throughout the suspension system perish over time, causing clunking noises and imprecise handling.

How We Fix It: We replace perished bushes with new rubber or polyurethane bushes. This restores tight, controlled suspension movement.

Typical Cost: £150-£600 depending on which components need replacing and vehicle type.

3. Brake Failures (18% of all failures)

Brake problems are serious safety issues and a common MOT failure point. At Car-Pol, brake repairs are one of our core specializations.

Common Brake Failures:

Worn Brake Pads:
Brake pads wear down with use. When they reach minimum thickness (typically 1.5mm), they fail MOT. Severely worn pads can damage brake discs.

How We Fix It: We replace worn brake pads with quality friction material suited to your driving style. We inspect discs for wear and damage. If discs are within specification, we clean and prepare the surface. If discs are worn or damaged, we replace them too.

Worn or Damaged Brake Discs:
Brake discs wear and can develop grooves, cracks, or warping. Minimum thickness specifications must be met.

How We Fix It: We replace worn or damaged discs with new discs that meet or exceed original equipment specifications. We always replace pads when fitting new discs to ensure proper bedding-in.

Brake Imbalance:
Brakes must work evenly on both sides of the vehicle. Imbalance causes the vehicle to pull to one side during braking and will fail MOT.

How We Fix It: We diagnose the cause of imbalance - often a seized caliper, contaminated pads, or air in the brake lines. We repair or replace faulty components, bleed the brake system, and test to ensure even braking.

Brake Fluid Leaks:
Any brake fluid leak is a serious safety issue and automatic MOT failure.

How We Fix It: We identify the source of the leak (often brake hoses, calipers, or master cylinder) and replace the faulty component. We then bleed the entire brake system and test thoroughly.

Handbrake Ineffective:
The handbrake must hold the vehicle on a slope. Worn cables, seized mechanisms, or worn rear brake components cause handbrake failure.

How We Fix It: We adjust or replace handbrake cables, free seized mechanisms, and replace worn rear brake components as needed. We test the handbrake on our ramp to verify it meets MOT requirements.

Typical Cost: £100-£500 depending on what needs replacing (pads only vs. pads, discs, and calipers).

4. Tyre Failures (12% of all failures)

Tyre failures are straightforward to diagnose but can be expensive if multiple tyres need replacing.

Common Tyre Failures:

Insufficient Tread Depth:
The legal minimum tread depth is 1.6mm across the central three-quarters of the tyre width. Many tyres fail because they're at or below this limit.

How We Fix It: We replace tyres that don't meet the legal minimum. We can supply budget, mid-range, or premium tyres to suit your needs and budget. All tyres are balanced and fitted to manufacturer specifications.

Uneven Tyre Wear:
Uneven wear indicates alignment problems, suspension issues, or incorrect tyre pressures. Excessive wear on one part of the tyre will cause failure.

How We Fix It: We replace the worn tyre and investigate the cause of uneven wear. Often this requires wheel alignment or suspension repairs to prevent the problem recurring.

Tyre Damage:
Cuts, bulges, or exposed cords in the tyre structure are automatic failures.

How We Fix It: Damaged tyres must be replaced - they cannot be safely repaired. We replace damaged tyres and inspect the remaining tyres for similar damage.

Mismatched Tyres:
Different tyre types or sizes on the same axle will cause failure.

How We Fix It: We replace one tyre to match the other on the same axle, ensuring both tyres are the same size, type, and have similar tread depth.

Typical Cost: £50-£150 per tyre depending on size and quality.

5. Exhaust and Emissions Failures (8% of all failures)

Exhaust system problems and excessive emissions are common failure points, especially on older vehicles.

Common Exhaust Failures:

Exhaust Leaks:
Holes, cracks, or corrosion in the exhaust system cause leaks. Any leak before the rear silencer will fail MOT.

How We Fix It: For small holes, we can sometimes carry out patch repairs using exhaust paste and clamps. For larger damage or severe corrosion, we replace the affected section or the entire system.

Loose Exhaust:
Broken or corroded exhaust mountings allow the exhaust to hang too low or move excessively.

How We Fix It: We replace broken mountings with new rubber hangers. If mounting points on the exhaust are corroded, we may need to replace that section.

Failed Catalytic Converter:
The catalytic converter reduces harmful emissions. If it fails, emissions will be too high.

How We Fix It: We replace failed catalytic converters with new units that meet emissions standards. We also investigate why the cat failed - often due to engine management problems that need addressing.

Excessive Emissions:
Petrol engines are tested for CO and HC emissions. Diesel engines are tested for smoke opacity. Excessive emissions indicate engine problems.

How We Fix It: We diagnose the cause of high emissions - often spark plugs, air filters, oxygen sensors, or fuel system issues. We repair or replace faulty components and retest emissions.

Typical Cost: £80-£800 depending on whether it's a simple repair or catalytic converter replacement.

6. Steering Failures (6% of all failures)

Steering problems affect vehicle control and are taken seriously during MOT testing.

Common Steering Failures:

Excessive Play:
Too much play in the steering wheel before the wheels start to turn indicates worn components.

How We Fix It: We identify worn components (often track rod ends, steering rack, or column bearings) and replace them. We then check and adjust wheel alignment.

Power Steering Leaks:
Leaking power steering fluid from hoses, rack, or pump will cause failure.

How We Fix It: We identify the leak source and replace the faulty component. We refill the system with correct fluid and bleed out any air.

Damaged Steering Components:
Cracked, bent, or corroded steering components are safety-critical failures.

How We Fix It: We replace any damaged steering components with new parts. We never attempt to repair or weld safety-critical steering parts.

Typical Cost: £100-£400 depending on which components need replacing.

7. Body and Structure Failures (6% of all failures)

Body and structural issues, particularly corrosion, can be complex and expensive to repair.

Common Body Failures:

Structural Corrosion:
Excessive rust on load-bearing parts of the body or chassis is a serious failure. This includes sills, subframes, suspension mounting points, and floor sections.

How We Fix It: We assess the extent of corrosion. For minor surface rust, we can clean, treat, and protect the area. For more serious corrosion, we may need to weld in repair sections or replace entire components. We'll always give you honest advice on whether repair is economically viable.

Sharp Edges:
Protruding sharp edges that could cause injury (often from damaged body panels or rust) will cause failure.

How We Fix It: We remove or smooth sharp edges, and repair or replace damaged panels as needed.

Insecure Body Panels:
Bonnets, doors, or boot lids that don't close securely or have damaged latches will fail.

How We Fix It: We repair or replace damaged latches, hinges, and catches to ensure all panels close and latch securely.

Typical Cost: £50-£500+ depending on the extent of damage or corrosion.

Our Approach to MOT Failure Repairs

At Car-Pol Auto Services, we follow a systematic approach to MOT failure repairs:

1. Thorough Analysis:
We carefully review your VT30 failure report and inspect your vehicle to understand all the issues.

2. Prioritization:
We explain which repairs are essential to pass the retest and which are advisories that can wait.

3. Transparent Quoting:
We provide detailed quotes with no hidden costs. You know exactly what you're paying for.

4. Quality Repairs:
We use quality parts and professional techniques. We don't do quick fixes - we do lasting repairs.

5. Pre-Retest Check:
Before you take your vehicle for retest, we check all the repaired items to ensure they meet MOT standards.

Contact Car-Pol Auto Services

If your vehicle has failed its MOT in Gloucester and you need expert repairs, contact Car-Pol Auto Services. Call +44 7892 679554 or +44 7402 953343, or message us on WhatsApp. We speak Polish and English.

Our workshop is on Barton Street in Gloucester, serving drivers throughout Gloucester, Cheltenham, Tewkesbury, Stroud, and surrounding areas. We specialize in MOT failure repairs and have an excellent track record of preparing vehicles to pass their retest first time.

Don't let MOT failures keep you off the road. Bring your failure report to Car-Pol, and let our experienced team get your vehicle repaired professionally and affordably.