MOT defect file
Tyre valve damaged or tyre not correctly seated
Last updated
Quick answer
The valve is damaged, missing or leaking, or the tyre has not sealed properly onto the rim. Cheap to put right, and it is the only thing holding the air in.
- Typical cost
- £10–£90 per wheel
- DIY viability
- Garage job
What you might notice
- A tyre that loses a few psi every week and needs topping up far more often than its neighbours
- Hissing you can hear, or bubbles when soapy water is brushed over the valve stem
- A valve visibly leaning over, cracked at its base, or sitting at an odd angle to the rim
- Vibration or an unsteady steering feel at low speed where a tyre has not pulled fully onto the bead
What causes it
- A perished rubber snap-in valve — they age and crack from the base, and are meant to be renewed with each new tyre
- Corrosion at the seat of a metal or sensor valve, common on alloy wheels that have been through several winters
- A tyre fitted without cleaning the bead seat, or without enough lubricant, so it never seats evenly all the way round
- Kerb impact bending the rim flange, or a damaged valve core after a heavy-handed pressure gauge or inflator
Advisory or failure?
A tyre valve that is damaged, badly misaligned or missing is a major defect, and so is a tyre that is obviously not correctly seated on the wheel rim. Where either fault is bad enough that the tyre could suddenly deflate or leave the rim, the grading is dangerous. The valve cap is not a test item, which surprises people, though leaving it off is how grit reaches the core in the first place. Note also that low pressure by itself is not a defect and testers do not fail cars for it, but its consequences are — the shoulder wear and the internal breakdown that follow chronic under-inflation are what eventually get recorded, and on vehicles first used from 1 January 2012 an inoperative pressure monitoring system is a major defect in its own right.
Can you fix it yourself?
Garage job
Diagnosis is a home job and worth doing before you pay anybody: brush washing-up liquid over the valve and around the bead and watch for bubbles, and compare each tyre's pressure with a decent gauge over a fortnight. The repair is not, because replacing a valve means breaking the bead, which needs a tyre machine. A valve core can be nipped up or swapped with a cheap tool if that is genuinely all that leaks, but do not chase a leak with a can of sealant, as it makes a proper repair messier and can upset a pressure sensor. When a tyre is unseated, insist the fitter deflates it fully and reseats it rather than adding air to force it round.
What it costs
A rubber snap-in valve is a pound or two and is normally included when you have a new tyre fitted, so on its own the job is £10 to £25 for the machine time. A metal valve or a pressure sensor stem service kit is £8 to £20, and a complete sensor is a different matter at £30 to £90. Reseating a tyre is half an hour of labour. The top of the band is a corroded alloy bead seat that has to be cleaned up properly, or a rim flange that has been kerbed out of shape and needs straightening before anything will hold air.
What happens if you ignore it
Small leaks are how tyres end up chronically under-inflated, and chronic under-inflation is the single most common route to a tyre that finally fails structurally rather than merely wearing out — the sidewall flexes, heat builds up in the shoulder, and the casing breaks down from the inside. A valve that snaps off at the base loses all the air at once. There is also a bill hidden in it: every month a tyre spends a few psi low, both shoulders wear faster than the middle, and fuel consumption drifts up with rolling resistance.
Common questions
- Is a leaking tyre valve an MOT failure?
- Yes. A tyre valve that is damaged, badly misaligned or missing is a major defect, and so is a tyre that is obviously not correctly seated on the wheel rim. Where either fault is bad enough that the tyre could suddenly deflate or leave the rim, the grading becomes dangerous rather than major.
- Does a missing tyre valve cap fail the MOT?
- No, the valve cap is not a test item, which surprises most people. It still matters, because the cap is what keeps grit and water away from the valve core, and a fouled core is one of the commonest reasons a tyre quietly loses a few pounds of pressure every week.
- Will low tyre pressure fail an MOT?
- Pressure by itself is not a test item and testers do not fail cars for a soft tyre. The consequences are assessed, though, because the shoulder wear and internal breakdown that follow chronic under-inflation do get recorded, and on vehicles first used from 1 January 2012 an inoperative pressure monitoring system is a major defect in its own right.
- How do I find a slow puncture at home?
- Brush washing-up liquid over the valve and around the bead where the tyre meets the rim, then watch for bubbles, and compare each tyre with a decent gauge over a fortnight. Avoid chasing the leak with a can of sealant: it makes a proper repair messier and can upset a tyre pressure sensor.
- How much does it cost to replace a tyre valve?
- A rubber snap-in valve is a pound or two and is normally included with a new tyre, so on its own the job is £10 to £25 for the machine time, since the bead has to be broken to reach it. A metal valve or sensor stem kit is £8 to £20, and a complete pressure sensor £30 to £90.
Warning lights behind this
This defect is what a tester writes down. What you see from the driver’s seat is a symbol, and it is worth checking which one, because manufacturers reuse the same shape for more than one system.
This is general guidance, not a diagnosis. The severity DVSA records depends on the specific fault found, so the same item can appear as an advisory on one test and a failure on another. Ask a qualified tester or mechanic to inspect the vehicle.
Has this been recorded on your car?
Check the full MOT history for any UK registration.