Torn CV Boot MOT Fail: Outer vs Inner Rules
Quick Answer
It depends on which boot. A split or torn outer CV boot is an automatic major fail under the May 2018 rules because grease is lost and dirt enters the joint. An inner boot may pass as an advisory if grease is retained and there is no joint play. Independent garages charge £40-80 to fit a new boot.
The constant velocity (CV) joint is what lets a front-wheel-drive car turn while still applying power. Each joint sits inside a rubber boot that keeps grease in and grit out. A split boot is one of the most common automatic MOT fails of the past five years, especially on cars over 60,000 miles. Run your reg through our free MOT history check to see if a CV advisory has been flagged before.
Will it fail your MOT? The exact rule
Section 6.1.7 of the DVSA MOT Inspection Manual covers driveshafts and joints. An outer constant velocity boot that is 'damaged so that grease will be lost or contaminants will enter' is classified as a major defect — an automatic fail.
Inner CV boots and gaiters are assessed slightly differently. A small split that retains grease and shows no contamination can be recorded as an advisory rather than a fail, provided the joint shows no play or knocking under load. Testers exercise judgement here, so condition matters.
- Outer CV boot split: major fail
- Inner CV boot split, grease retained: advisory possible
- Boot split with joint play: dangerous fail
- Old grease leaking but boot intact: advisory
Why CV boots tear
CV boots are made of moulded rubber or thermoplastic that flexes hundreds of thousands of times over a typical service life. UV light, road salt and oil contamination all degrade the material until the convoluted folds eventually crack.
Outer boots fail more often than inner ones because they sit closer to road spray and operate at a wider angle on full lock. Heavy steering use (city driving, parking manoeuvres) accelerates wear, which is why minicabs and driving school cars are common candidates.
How to spot it before the test
Park on level ground with the wheels on full lock and shine a torch into the wheel arch. The CV boot is the black concertina-shaped rubber where the driveshaft meets the wheel hub. Look for cracks, splits or a fan-shaped pattern of grease on the inside of the wheel rim.
On the road, a clicking sound on full lock under power is a sign the joint itself is contaminated and worn. By that stage replacement of the entire driveshaft is usually needed and the boot-only repair window has passed.
- Inspect both wheels on full left and right lock
- Look for grease spray on the inner wheel face
- Run a finger along the boot folds for splits
- Listen for clicking on full lock under acceleration
- Check for rusty staining on the driveshaft
Cost to fix before MOT day
A boot-only repair at an independent garage costs £40-80 if the joint is still serviceable. Some garages use stretch-fit boots that don't require driveshaft removal, although a proper repair involves splitting the joint, repacking with grease and fitting a moulded boot.
If the joint is already noisy or shows play, a complete reconditioned driveshaft is the more honest fix at £120-200 fitted on a mainstream car. Main dealer prices for a new shaft routinely run £350-600, so an independent specialist almost always wins on value.
- Stretch-fit boot only: £40-60 fitted
- Boot with proper joint clean and regrease: £80-120 fitted
- Reconditioned complete driveshaft: £120-200 fitted
- OEM driveshaft from dealer: £350-600 fitted
- Both shafts replaced: £200-350 at an independent
MOT history clues for buyers
Recurring CV advisories are a strong sign the previous owner was kicking repairs down the road. Run any used car through our free MOT history check and look for 'CV', 'driveshaft' or 'joint gaiter' in the advisory and fail text.
Compare against our common MOT faults database. High-mileage Ford Focus, Vauxhall Corsa and Renault Clio examples often show CV boot advisories from around 70,000 miles onwards.
Pre-test self-check
If you have access to a torch and 10 minutes, you can save yourself a fail. Turn the wheels onto full lock and inspect the boots front-on. Repeat for the opposite lock. Any visible split on the outer boot will fail the test, regardless of mileage or age.
If the joint clicks on full lock under power, do not bother with a boot-only repair — book the driveshaft replacement instead. A boot fitted to an already worn joint will fail again within months.
Frequently Asked Questions
Will an inner CV boot split always be an advisory?
Not always. If grease is being thrown out, contaminants are visible inside the boot or the joint shows any play, the inner boot is a fail too. Only intact-but-cracked inner boots with retained grease typically pass as advisories.
How long can I drive with a torn outer CV boot?
Days, not weeks. Once grease escapes and grit enters, the joint wears rapidly and the click on full lock starts within 100-500 miles of normal driving. Replace the boot before that point and you keep the joint.
Are split-fit replacement boots safe?
Stretch-fit boots are accepted by most garages and last several years if fitted correctly. Moulded one-piece boots installed during a proper joint service last longer (the original design intent), so it is worth paying the small premium.
Why does a driveshaft cost so much more than a boot?
The shaft is a precision part with two CV joints, splines and a press-fit hub interface. Reconditioned units balance cost and reliability and are usually the right call once a joint is noisy. Whole-shaft replacement avoids labour going twice.
Can I replace a CV boot myself?
Yes, with basic tools and a haul jack, but it is not a beginner job. The joint needs splitting, cleaning and repacking with the correct molybdenum grease. Many DIYers find a stretch-fit boot saves the disassembly headache.
Inspect your CV boots a week before MOT day, fix any outer splits straight away, and run a free MOT history check on any used car you are considering buying.