Help me figure out what is wrong with my Wheel's air pressure
 

Hi Guy,

My back left rear wheel is losing air (about 2 pounds) every 5-7 days. I have a 2012 E 350.

I have gone to two different tire shops and mercedes and they cannot find the problem or leak. The last mercedes dealer said to drive the car until it loses about 6 pounds and bring the car back in to the dealer. I don't know how this would help if they couldn't find it in the first place.

Do you guys recommend some way to advice these tire shops or mercedes on how to find the leak?

Also, there has been talk of recommended air pressure for the E class on these boards. The 2012 only has the air pressure stated on the pillar of the driver side door, there is no air pressure stated in the gas tank.

You could have a hairline fracture inside the rim itself caused by either stress or a strong impact (pothole, curb, etc). The only way, that I know of, to check for hairline fractures is to remove the tire from the rim itself and inspect it by eye or via X-Ray.

Take the wheel off the car, inflate tire to 50lbs and submerge it in water. Voila.

+1

Yep, submerge the tire/wheel assembly and look for bubbles.

The other option is to spray it with soapy water and look for bubbles, but that's not going to be nearly as quick or effective.

I assumed taking it to two tire shops and to a mercedes dealer would have sufficed as to the testing of the wheel. But I guess I am wrong?

Rarely does anyone any longer submerge the tire/wheel in water to find leaks. Used to be routine and shops used to have tanks designed for this. I would find one that has a tank and request that it be submerged. Slow leaks are difficult to find with soapy water sprayed on and that seem to be the norm today.

Thats what I was about to recommend....:y