Checked my tyre pressures at the weekend, all good. A few miles into a journey, the tyre pressure loss warning came up and I stopped to check. The suspect tyre had lost about 0.8 bar in 10 miles. I pumped it up again and continued for another 50 miles without getting another warning. The warning came up again shortly into my next journey but that was short so I carried on to my overnight stop. The tyre was completely flat the next morning. I pumped it up again, inspected carefully for any embedded objects or damage finding nothing, and did 60 miles back home with no issues. The tyre was still at full pressure afterwards and still is the next morning!

Any ideas what could be going on?

Edited 12 January12 Jan by D402

Either a bad seal around the tyre bead, leaking valve stem or screw/nail in tread.

Leak partially re-sealing while running.

Jack wheel off ground and check carefully for foreign objects in tyre.

Test valve stem with saliva or soapy water for leakage.

The car does not happen to have Self seal tyres from the likes of Continental fitted does it? Or mouse or tyre weld already in it .? Time to flash the cash and have the wheel off the car and in the water back, or squeezy in water sprayed if not doing youself. It might well be the valve. Always worth over inflating then reducing pressure to see if that seats the bead.

Edited 13 January13 Jan by Evolution13

My 2025 Kodiaq 2.0 litre Diesel Sportline is not even 1 year old. A couple of weeks ago I got a message on the dash advising a drop in pressure on the nearside rear tyre. i pulled into a service station to re-inflate the tyre, and as luck wouldn't have it, I saw immediately a machine screw or nail protruding from the tyre tread. This was at the beginning of the holiday season and I decided not to go far. I checked over the next few days and surprisingly when I checked the pressures it told me all were within specified range. Clearly the screw/nail was providing a seal against further pressure loss.

Then my dilemma. It's a heavy but powerful car. I tend to drive 'spiritedly' and regulary travel to France and Germany on holiday trips. Would I be completely comfortable at Autobahn speeds with a repaired rear tyre? Wiser counsel prevailed and I got in touch with Black Circles who offered the exact same brand and size of tyre to be fitted at a local garage near me. The job was completed this morning and I have nothing but praise for Black Circles and also the local tyre fitting place. Perfect service in this day and age !! I can't recommend them highly enough.

We've had a very busy month and driven nearly 2000 miles with no further pressure loss from that tyre. I can only think that the valve didn't seat properly after I first checked the pressure then sealed again once the tyre was reinflated.

A useful tip for checking valve stems I have used for more years than I care to say is to smear a trace of saliva (or soapy water for the fastidious) across the top of the stem to form a film, then leave for a few seconds before replacing the cap.