Tires randomly leak air

[MMC2ELGIN]

A little over 3 years ago I had my 2005 Buick LaSabre OEM tires replaced in preparation for a long road trip. I never had any problems with the old tires,but within a few months of getting the new ones the trouble began. I would be losing anywhere from 10lbs to almost totally flat ,usually just one tire at a time and in random tires. It can happen within a week, but it might be as long as a couple of months before one gets low.I've taken my car back to the place that sold me the tires several times and they have yet to find any leaks when immersing in water or other issues like rotted valve stems or leaking valve cores,no cracked ,corroded or bent rims,no punctures,no tire labels left on.I even considered that somebody might be doing it so I set up a "trap" that would show if the valve caps had been removed, nope.I've had to air up my tires so many times that I've worn out and had to replace one of those plug in air compressors. Has anyone else had this trouble after replacing their original tires ?

 

[HotZ28]

Have you got chrome wheels?

 

[MMC2ELGIN]

Have you got chrome wheels?

I've still got the OEM 16" Rims (Alloy?) along with the wheel covers that came on it. The replacement tires are "Cooper" brand if that makes any difference and they are marked with the size that should be on there.The car has never been modified or wrecked and overall is in great shape.

 

[gnhbodyguy]

They should have given you new valve stems free with a tire purchase. Alloy wheels do not have wheel covers. Only steel wheels do. I believe all last generation LeSabres had alloy or chrome wheels. I would have the tire shop pull the tires off the rims and you inspect each wheel along the seal line. By sight and touch. Tire stores can also apply a sealing liquid.

 

[Terasec]

slow leak might be hard to detect unmounted,
once you see a drop in pressure i would spray a soapy water mixture all over the tire while still mounted and see if you can spot any bubbles

 

[MelsRegal]

did they break the tires off the beads and check the tire bead area for any kind of roughness where it contacts the rim?