Ok, I am officially pulling my hair out.

We have an 08 T&C with the tire pressure sensors. Since last winter when I bought new tires, we've had a problem with one particular tire literally going flat overnight when the ambient air temperature drops below freezing. The colder it is, the faster it deflates.

I've taken the vehicle back to the tire shop several times and they cannot find a leak anywhere. I even watched as we SUBMERGED the tire (on the rim), properly inflated for nearly 20 minutes with nary an air bubble/leak to be found.

I've inspected the tire and the valve stem myself and even replaced the valve core but have found nothing to indicate any air is leaking.

Obviously, it's leaking somewhere, but where!?!

Any ideas? Once the ambient air temperature is at or above freezing, the tire holds pressure just fine.

 

Try something for me......

Take the valve stem caps off over 2 or 3 days, and see if that helps. The cores tend to sit very high in the stem, and Ive seen several of them that depress the core when screwing the caps on. Like everything else, cold contracts, and allows the air to escape past the cap....

 

giving it a try tonight!

 

Well, that didn't help. Was nearly as flat as a pancake this morning. Any other ideas?

 

Just a stab in the dark. I'm thinking maybe a tire to rim bead problem. Dissimilar materials (rubber and metal) reacting differently to the temperature.
On my 00 I have a slow leak due to bead corrosion on one of the alloy rims. The tire shop buffed most of it off but it needs to go back again.
Maybe your rim has some corrosion or the tire bead itself was not formed correctly when manufactured?

 

Youre on the right track.......

I have this same issue in the shop this morning (And I dont know why I didnt think of it yesterday).....

Where else, aside from rim to tire do we have rubber to metal contact????

THE FERRULE NUT THAT HOLDS THE SENSOR IN

Its a 12 mm socket, try tightening the sensor to the wheel.If it is not tight enough, cold causes the rubber o-ring to contract and the air leaks out. as the air is escaping, it freezes, and forms an ice "Bridge " that allows the rest of the air to escape. when the BRIDGE DEFROSTS, The seal is restored. which is why you cant find a leak. If you checked it with soapy water at 3am on a frosty night ....You would have found it. I left the tire out in the parking lot and buried it in the snow for two hours, dug it up, and checked it right in the lot.... By the time I got it inside to fix it, it wasnt leaking anymore.

 

all righty then! We'll give that a try too! Will report back. @mgbmike, I don't think there's any corrosion but I'll check that too!

 

Well, tightening the ferrule nut on the sensor seems to have done the trick! Tonight will be a good test as well since it's expected to dip into the negative temps.

One question though. What's the torque specifications for the nut? I tightened it a little bit but didn't go overboard because I didn't know how MUCH to tighten it. I'd like to snug up the other sensor's as well.

 

Laugh as you will, but all I have ever used is a 1/4" ratchet, and a Firm tug with just my Ring finger.I'm sure there is a Torque spec for it, But in all honesty,....I dont think I have ever looked for one.

AND ALWAYS REMEMBER....PLASTIC STEM CAPS ONLY!!!!!!!

 

I'll bite... why plastic stem caps only?