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A slow leak I'm having trouble finding

    I drove my car March 28 for the first time since October 12.  3 tires were under-pressure 1.5 - 2.5 psi; the 4th, the driver's side rear, was 9.5 psi low (25.5 instead of 35).
I've had 2 incidents of slow leaks (in 18 years), the first a puncture I plugged, the plug slowly failing a few years later; the second a defective valve (I put it in the tub but didn't get the water high enough to cover the valve - a llantera diagnosed it.)
This tire looks okay, squirting soapy water on the valve doesn't reveal a leak; it has lots of tread, has only 19K miles use (is rated 540), is 13 years old.
Have I overlooked a possible cause of this leak?

Don’t worry about it!
I too park cars for 6 months at a time.

Since you should check and set tire pressure at least once a month anyhow, I’d leave it alone and monitor it every month. You’re only talking about 1 psi or so every month.

I’ve had situations where the seepage/leak can be exacerbated by the position of the tire while parked.

Choose your battles, carefully. Concentrate on finding something else to fix for now.

"This tire looks okay, squirting soapy water on the valve doesn’t reveal a leak; …"
Be Sure You Wiggle The Valve Stem Around Slowly And Observe While Squirting.


A leak that slow can be hard to find. Just a bubble once every minute or so. You really need to over inflate it and put the whole thing in a tub and then watch. I had one like that around the valve stem but also check the valve core. You can also get a bad seal around the wheel from rust that can develop on its own from sitting. Then it could also be a small nail or chunk of metal. I had one on the trailer that I didn’t find for a couple years and just added air every no and then. Also the alloy wheels themselves can leak and need sealing.

I’ve known wheels to leak, though rare.
But still, the water bath would reveal that.

I would advise not using a leak sealer that is squirted in through the valve stem. I think these sealers would throw the tire out of balance. I had a basketball that kept losing air so I gave it a shot of tire sealer. It dribbled like a bowling ball after that.

Your tires are considered too old to be safe by today’s standards. Replace the tires and your problem will probably go away.

“This tire looks okay…is 13 years old.”

Leak or no leak, you couldn’t pay me to drive on 13 year old tires.
At this point, the rubber has hardened to the point where traction–especially on wet roads–is severely compromised.

Don’t you place some value on your safety, and on your life?

With all due respect, those tires are DANGEROUSLY old

They must literally be “rotten to the core”

Get rid of them NOW

Those tires are surely dry rotted all to hxxx and that makes them as dangerous as bald tires.

The only way they may not be dry rotted would be if the car is garaged all the time and out of the sunlight.

Maybe the rubber in the aged tires has hardened and there are bead leaks.

I agree with those who say these tires are too old. In addition to dry rot being a possible cause of the slow leak, these tire could fail catastrophically if you hit a bump… especially on the highway… or even when braking in an emergency situation. If someone’s child runs out in front of you and you have to slam your brakes on, you do not want a tire going “pop”.

Yeah I missed the age part so time for new tires anyway. Its a reading comprehension thing. I read what I want to read regardless of what is written and then only read every other line or so. I like bullets in bold and expect someone to get to the point in the first line and paragraph. A lot of people don’t read any more than that. I loved the long three page letters of complaint when it should have been condensed to two paragraphs and a thank you.