Slow Puncture Even After Using Tyre Repair Sealant? Try This!


So Deflating

Slow punctures are undoubtedly one of the most annoying problems every vehicle owner will experience at some point. Many of which do consist of a traditional puncture that’s caused by debris on the road, however we recommend also checking for another puncture gremlin that’s not actually quite so well known. If you’ve used temporary tyre repair sealant and still have a slow puncture, read on.

The Possible Culprit

Tyre valves contain a core inside them known as a Valve Stem Core, that over a long period of time can often begin to leak slightly, resulting in a slow puncture. The most likely cause for this is the rubber seal on the valve turning brittle and hard from age and is therefore not as flexible as it once was when new. Dirt can also be the culprit when it comes to faulty stem cores especially when one forgets to refit or loses a valve cap, but the good news is that the leak can be easily fixed and its very inexpensive to do so.

The Fix

Tyre valve repair kits can be found as little as £4 online, they often include a valve core removal tool, thread tap and thread dye (tap for the inner thread on the tyre and a dye to clean the thread on the valve) along with a set of the actual valves themselves.

How to Replace a Valve Stem Core

  • Remove the plastic valve cap and remove all air from the tyre by pressing the centre of the old valve in with a pen or screwdriver, this may take a while. WARNING – Do not use the valve core removal tool with the tyre still inflated, otherwise the core will fly out at supersonic speed and hit you right in the noggin!
  • Once all air is removed use the removal tool and unscrew the old valve core.
  • Clean the tyres valve thread by using thread tap tool included in the kit, screwing all the way in and out twice.
  • Fit the new valve core and screw it in until tight.
  • Fill the tyre air up to the correct psi that’s rated for the car, pressure guides can usually be found on a sticker in the door sill or inside the fuel cap.
  • Spray some soapy water onto the valve and check for any bubbles.
  • If no bubbles are present, refit the cap.
  • A few days later, take a pressure reading from the opposite tyre and then take one from the repaired valve to see if they’re the same and that the problem has been resolved.


It’s worth noting at this point that replacing a valve isn’t the only possible reason for a slow puncture, they can also be caused by:

  • Corrosion on the wheel bead
  • Tyre bead damage
  • Old tyres with ‘dry rot’ – Dry rotting is when the tyres start to crack from old age and UV damage, this can eventually lead to leaks let alone be dangerous!
  • If you do use tyre sealant first, make sure in the product description that it’s safe to use on alloy wheels as some are known to cause corrosion (look for a water based one).
  • Budget tyres are known to age quicker than good quality tyres


Hopefully these tips will help you out and you’ll no longer be having slow puncture issues!


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