My passenger front tire keep on slowly losing tire pressure. The TPMS gives a warning light after about 2 weeks of daily driving. I would then add air and it would be okay for another 2 weeks or so before the warning light comes on again. The other three tires are stable. Anyone know what could be going on?

 

At the risk of stating the obvious, you might have a very small leak. I'd take it to a quality tire shop and have them take a look.

My passenger rear starting doing the same as yours, then the drop in pressure became precipitous. For a couple of days I had to add pressure every morning. 20 minutes later the tiny nail was removed and patched, and I'm all good. Actually, better than good as I'd purchased tires there a couple of years ago (for a different car) and the fix was "no charge." Can't beat that.

 

yeah, i'm hoping also that you at least checked it for an obvious nail/puncture, correct? so i'll bite my tongue for now on giving you sh*t, and just give some advice.

if you DONT have an obvious puncture, first i'd try slathering soapy water around the wheel edge and esp around the valve stem and look for bubbles. if that doesnt work, i'd take the wheel off and put it in a big (bath)tub of water and look for bubbles. this is what i did and found where the leak was - turns out the installer forgot to remove a tag (?) that was on the inside lip of the tire, preventing it from seating properly. was an EXTREMELY slow leak, but damn if i didnt track down exactly where that tag/leak was by using the bathtub approach.

 

+1

To find the leak yourselft - mix some dishwashing soap/water in an empty water bottle. Poke a hole in the bottle. Spray the solution on the suspect tire and look for an area where the leaking air will create bubbles. You may have to move the car fwd to address both halves of the tire. Short of this the other method is to remove the tire and set it in some water to find the leak.

 

Couple weeks ago after returning to work from my lunch break I noticed a hissing from my right front tire when I got out of the car. Turned out that the rubber valve stem had cracked at the base near the rim. Still don't know why it failed because I never hit anything in the road or took any turns aggressively. I guess it was it's time to go. Luckily it held until I parked at work. It was a minor inconvenience to remove the wheel and have a co-worker take me to the local American Tire shop, whose manager fixed it for free, but it's all good for now.

 

To summarize the previous statements and answer your original question:

YOU HAVE A HOLE IN YOUR TIRE!

 

I had a very slow leak on a new PS2's a couple of years back. Michelin uses a white label fixed to the inside of the tire for inventory control or something else. On only one of my tires it was very close to the bead of the tire so when mounted it didn't quite seal entirely. It was so slow that the only way to discover was to dismount the tire and use the tried and true soapy water method to discover.

 

Closely-related topic: I recently learned how useful the TPMS can be. Driving in the fast lane on the 5 freeway (five or six lanes), I got a big warning that I had a flat and to my surprise it proceeded to count down the dropping tire pressure, 38, 36, 34 etc. I quickly worked my way across lanes toward an exit as it reached 22, 20, 18. I got to the first light. 14, 12. Cut across traffic and rolled into a gas station and its air/water station, 11, 10. Anyhow, found out there was a tire place 2 blocks away, added air, and made it there easily. 20 minutes later I was plugged and back on the road. Would have been VERY different scenario without TPMS, since I didn't feel the flat until pressure was WAY down, and would have been stuck on the wrong shoulder of a very busy freeway.

 

Well, I took my car to the dealer, they took the tire off, examined it, no nails or obvious punctures and then did the soapy water thing with no bubbles. They said they can't find anything wrong with the tire or the TPMS! At least they didn't charge me for examining it and got a free car wash. So far the tire is holding pressure. Just keeping my fingers crossed!

 

It could be your schrader valve not seating properly. I've had that happen. Remove the cap on the valve stem and put a little soapy water or saliva on the valve stem opening. If it bubbles you found the culprit.

I always keep a schrader tool and a couple of valves in my tool kit.

 

Very slow leak is a nail in your tire. Patch it.

 

Never let the dealer wash your car.

 

Could you elaborate? My dealership has a guy with a spray nozzle, not automated.

 

Dirty wash towels, dirty dry towels - why take the chance...or if you want to, watch how they do it then you can come to your own conclusion.

 

Yep... they like to leave swirl marks with their dirty rags. Don't fall for the free car wash.