I had it checked at a tire place they didn't find a leak/nail. About every 2-3 weeks it shows low, and every time the pressure is about 30 psi. I fill it to 38, the warning goes away. This has happened 4 times. What could cause that to happen over and over? Thanks in advance.

 

If was me, I'd take it to a different tire store. You obviously have a leak that should be detectable..

 

yup, also have em check around the fill stem may be leaking out the schrader valve also

 

+1 for the stem. Often overlooked.

 

Yeah I thought of that too. It just may leak really slow, and when it sets off the alarm at 30 psi I fill it up again and start over. The tire place may have inspected it and brushed some water on the tread looking for bubbles. Question: if it's the stem does that mean I have to buy another pressure transmitter too? Those cost like $50 don't they?

 

I agree, if there is no sign of a puncture on the tire itself, I'd think it's the valve. It can be a very slow leak. You'll just need a new valve. Can search real OEM here for the correct stem needed for your R56, but otherwise they should be able to do it easily at a tire shop.

 

Sometimes some dirt/debris gets in the bead area (or was there originally) and creates a slow leak. Have them un-mount, clean the bead area, and remount.

I had this issue with my wife's jeep a while back.

 

Although a stem leak is the likely culprit, I remember reading about leaks that occur through the metal of wheel castings themselves. I think I'd try a different tire shop, have them submerge the whole thing and let it sit for a while to see where bubbles emerge. Or you could use a laundry tub or bathtub if you have one!

 

If you don't have tub to submerge the tire try mixing a dishwashing soap and water and either use a spray bottle or brush to generously coat the tire and rim. The leak will be fully visible with bubbles from the solution. I would also inflate the tire to about @40lbs.

 

Obviously you need to fill with nitrogen which won't leak out ...... didn't you see the advertisements at the tire shop?

 

The last time I had a stem valve leak it simply required tightening. Does that not work with TPMS stems?

 

a TPMS stem has an o-ring and this can be the problem ..... a simple not TPMS valve insert can be tightened or even replaced without taking the tire off the rim. I'm not sure a TPMS valve can be serviced without unmounting the tire.

 

I went out to the trailer where my OEM wheel/tires are stored and had a look. The valve can be loosened and tightened with an ordinary valve core tool. Beyond that I did not experiment.