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Tire with intermittent slow leak?

'99 Ford Escort. Tires are only a year or two old and look pretty good. I hope you will not neeed the tire size to answer this question because I near about froze my fingers off pumping up the tire early this evening and I forgot to note the size and it’s cold windy and and dark outside and I don’t want to go back out.



Two or three times in the past two weeks one tire seems to have leaked down over a couple of days from specified 29 PSI to 16 PSI. Holds pressure for a few days, then goes down over a couple of days. I took it to the national chain shop where I bought it and they tested it in the water tub. No leaks found.



So, is there such a thing as an intermittent leak, or it is leaking continuously and I am just not noticing until it’s way low? And if it is leaking continuously, why did they not find it (I watched, and the guy seemed up to the job)?



Suggestions?

Sometimes a tire’s valve will leak in cold weather due to ice forming inside the valve. When it warms up during the day, no more leak.

Well! That’s interesting. Does “inside the valve” mean inside-the-tire side of the valve, or merely in the external inside where the valve stem is? And for fixing it, I suppose if it’s external, then I just have to thaw it and dry it, but if it’s internal then I should have the valve replaced. Right? And how do I prevent it’s happening again?

If there is a nail or screw in the tire, it can leak at a different rate when the car is parked with the nail/screw on the bottom.
Let all the air out of the tire. Leave the nail or screw in-- it makes a pretty good plug. Use a can of Fix-a-Flat, and drive to a station which has pressurized air and pump the tire up. It should be fine.

slow leaks are often misatributed to the tire when it is rim corrosion that is the problem. the tire should be removed, inspected internally of course, look for damage to the bead and of course polish off and clean the rim sealing surface. and valve stems do leak too, so replace it when the tire is removed.

Let me add one I had. If you park close to a curb and the valve hits the curb, it is possible that the valve will leak only when it is being bent by touching the curb. It took me several weeks to figure out that one.

Factory steel wheels? I ask only because I’ve had aftermarket wheels which got corroded where the tire met the wheel (bead) and leaked like this. I’m thinking that since you took it to a tire dealer and they couldn’t find a leak, that Joseph’s curb suggestion is a good one. Only real way to stop it completely (for me) is to let all of the air out . . . sand the wheel and tire where they meet, change the valve (sand that where it goes in), re-fill with air to proper psi, and check it. Rocketman

Thanks for the ideas. FWIW, valve bumping into curb is extremely unlikely. First, there is no curb. Second, when the tire was bought the shop used a short valve which sits way down inside the wheel cover; hard to reach for checking pressure or attaching the pump.

Rim corrosion is a good possibility. They are factory steel rims. One of the rims was bought from a salvage yard about 18 months ago; can’t be sure which one. But again, why could the shop not find a leak? Same for a puncture, with the item still embedded inthe tire.

I’ll be off to the tire store again this morning. If they still can’t find a leak I plan to have them remove the tire so we can inspect/dress the rim and remount/balance the tire. Maybe I’ll bring my own sandpaper :>) At least I’ll come out it with a proper length valve.

are they alloy rims?? mine leak no matter what is done? my mechanic wire brushes them and adds more glue, down the road they rims leak again. i think winter has a lot to do with it? to ck. for rim or stem leak ( works better if taken off car) put liquid soap around rim ( better if you can bring it in to a warm place, the soap works better warm. then wait a little while and see if any bubbles appear? give it time! i remember years ago i bought a tire from sears brought the car home cut the grass looked at the tire it was flat as a pancake? brought the tire back-- they put it in water, no leaks got home , went about my business, one hour later tire flat again? it was somehow the weight of the car that doomed the tire to go flat!!! you figure? got a new tire no problems? best of luck

Update. This time, after again finding no leak, the tire store noticed a bit of bend in the edge of the rim – on the inside! – and they finally found a slow leak there. I’m chasing down a replacement rim from a salvage yard. If that turns out not to be the problem, I’ll post back when I get the final fix.

(So how do you bend the inside of the rim? Beats me, but Dad was doing some interesting driving before he handed the car down to me.)

“So how do you bend the inside of the rim?”

My son did it by trying to straddle a curb.

That’s a dad for you. Thanks for letting us know how it turned out.