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2010 Subaru Forester front left tire looses pressure faster than other tires

I have a 2010 Subaru Forester that looses pressure in the front left tire much more quickly than the other 3 tires. For example, I just filled up all 4 tires to 33PSI, and when I checked it a week or two later, the front left was at 26PSI, while the other 3 were still at 32-33PSI. In the past, the tire pressure light has come on because the front left tire managed to get as low as 16PSI, while the other 3 tires were still at ~26PSI. Any ideas? Is it possible to have a small leak that leaks a couple PSI per week?

Yes, I’ve had slow leaks on two of my vehicles and was unable to find the puncture sight. My mechanic was able to find both and repair them.

Ed B.

Yep, could be the valve stem, small nail/brad, small leak at the tire bead, or (least likely) a porous wheel. A tire shop should be able to find it with a water bath.

Sounds like a typical slow leak, have your local tire shop or garage fix it for you.

Could also be a dinged/bent rim. The hillbilly way to fix this is Fix-A-Flat, but a good tire shop should be able to do a proper repair for not much more.

+1 to all of the preceding comments.
Whether it is a defective tire valve, or a dinged wheel rim, or a tiny, previously-unnoticed puncture, dunking the tire in a water bath should enable a tire shop to figure out where and how the tire is losing air.

Sometimes, a leak can be from a cause that is totally unexpected. As an example of what I am talking about, many years ago, I had a persistent–albeit very slow–leak from a tire on a new car. What was finally discovered, after taking the tire off of the wheel, was that the wheel supplier had left a small paper label on the area of the rim where the tire’s bead makes contact with the wheel rim. The incredibly thin layer of paper was just thick enough to cause the tire to lose a couple of lbs of air pressure every few days.