There’s an air leak in one of the the TPMS wheel sensors on my 2013 C5 Tourer X7. It takes a couple of weeks for sufficient air to leak to illuminate the low tyre pressure warning system. When washing the wheels I can see a few air bubbles around the valve stem, signifying the leak. Do I have to buy a Citroen replacement TPMS sensor complete, or is there a quality after market equivalent that would be suitable. I’ve seen just the valve stem, washer seal and valve core available for £5 or less, including one kit on eBay,which quotes a Citroen part number. Have you tried these, and are they suitable?