Over the last few months one of the tyres developed a slow leak - the pressure warning would come on and I'd have to pump it up every month or so. The tread was getting down to not much above the legal minimum so I bought 4 new tyres a couple of weeks ago assuming that this would fix the problem.
To my surprise the slow leak continued, or maybe got worse, losing around 1 psi per 24 hours. As I'd just bought the tyres I took it back to the tyre fitting place (Kwik-fit) and asked them to investigate. They couldn't find a leak in the obvious places around the rims or any puncture, but took the tyre off the rim again and discovered that the pressure sensor itself was leaking. I didn't know that these are attached to the bottom of the valve stem. They replaced this and it seems to be ok now, so I guess their diagnosis was correct. It seems a bit odd to me, but I think this is the first car I've had with tyre pressure sensors fitted, so it's all new to me. The more automatic systems cars have the more there is to go wrong, of course.
To my surprise the slow leak continued, or maybe got worse, losing around 1 psi per 24 hours. As I'd just bought the tyres I took it back to the tyre fitting place (Kwik-fit) and asked them to investigate. They couldn't find a leak in the obvious places around the rims or any puncture, but took the tyre off the rim again and discovered that the pressure sensor itself was leaking. I didn't know that these are attached to the bottom of the valve stem. They replaced this and it seems to be ok now, so I guess their diagnosis was correct. It seems a bit odd to me, but I think this is the first car I've had with tyre pressure sensors fitted, so it's all new to me. The more automatic systems cars have the more there is to go wrong, of course.