Several months ago one of my 20" toyo tires was flat when I came out of work. Being a high school teacher, I thought that perhaps it was a students involved situation. That came as a surprise in that as a teacher of over 37 years, nothing has ever happened to any of my vehicles, while parked at school. Also I found it strange that they would let air out and put the chrome valve cap back on. Well, over the weekend, the same thing happened, with the car parked in my garage. So in both instances the tires went flat, I filled them back up and they held air. This happened months apart. What is going on? Anyone?

 

Did you happen to get new tires recently?

If not, then the valve stem seal may have dry rotted and started to slowly leak. If you have some spare time get a spray bottle filled with soapy water and spray the beads and the valve stem and look for bubbles, that will show the leak.

 

There was a previous thread about this... had to do with a loosen nut on the TPMS sensor. If I recall, happened mostly while the car was in motion from centrifugal force. Here is an exploded diagram of the tire and TPMS sensor. It may be loose or the outer grommet may have deteriorated allowing air to leak out slowly in either case. BTW the numbers inside the box in the diagram are the torque amounts.

 

I know this is an old post, but just wondering if you remember what tire it was on? This just started happening to my SC again so I started doing some research. Looks like it occurs mostly on the front-driver's tire.

 

I had slow leaking with tires on a Saab. The alloy wheels had begun to corrode and caused a break of the bead. This happened on different wheels on the car at various times. Also,on my OEM SC430 wheels I had leaking and found that two wheels had hairline cracks. This was on an "03 this year.

 

The tires would lose 2 psi easy every 2 to 3 weeks. Over time, you can lose 10 psi. So slow leaks can be mistaken for normal psi loss.

Hence periodic check of pressure is needed and fill as necessary.

 

I had the same issue about a year ago, but after 4 reputable tire shops, a mom/pop tire shop discovered it was the tmps sensor (same case as earlier post). The first thing the old guy did was go to the valve stem, he shook/pulled on it, then said "here's your problem"...lol. He mentioned that he had run into that issue with alot of the newer cars equipped with sensors.They took off the tire, snugged it down (inside/out),rebalanced,charged me $20 bucks & sent me on my way. I also had a co-worker with an older IS model doing the same thing. His issue was the chrome peeling from around the edges of the factory wheels.He talked to someone @ Sewell (Dallas) & they replaced the rims for free !!!