Faulty tyre valve stems found on a car's tyres often cause air leakages over an extended amount of time. When you notice a faulty valve stem, it's important to remember that it doesn't necessarily mean having to replace the whole tyre. When purchased separately, valve stems are pretty much inexpensive, and if you are willing to manually install them instead of going to a repair shop, then the cost of this whole process will be minimal. Here's the steps needed in order for you to install your new valve stems, like from Estry Trading Company.
Removing the tyre to access the valve stem
First of all, you need a tyre iron in order to loosen each of the lug nuts present on the wheel's cover. On most cars there are 5 lug nuts present. Make sure not to completely remove the nuts yet, because you'll first need to raise the car up using a jack, until the wheel you want removed is off the ground.
Once the wheel is off the ground, remove the nuts completely with the tyre iron, and place them somewhere where you can easily find them later on. Slide the wheel off the studs, and lay it down on the ground with the nuts part facing up.
Installing the new valve stems
You need to unscrew the cap, found around the margins of the plastic bead, then insert it back into the stem and push down on the small needle-type section in the center in order to deflate the tyre. Hold this position until the tyre is completely deflated.
Using a crow-bar, break the plastic bead of the tyre, and make sure that the tapered edge of the crow-bar is pointing towards the tire, otherwise you might damage the rim. Hold it in this position while hitting the end with a hammer until you can hear a 'pop' sound, and then simply pry it loose from the rim.
Using a pair of pliers, pull out the old valve stem. Before applying the new one, make sure to use dish soap or a lubricant to coat the new stem. Make sure the new tyre valve stem is in position, then pull it through and lock in place using the pliers.
Put the tyre back onto its rim, then secure the wheel onto its car mount using the lug nuts. Fill the tyre back up with air and finally crank down the jack in order to bring down your car. Once all that is done, your new tyre valves are ready to go!