I have a 2007 RX 350 with 18" Cooper tires. I had a hole in it repaired by Sears (they used a hybrid plug/patch for the repair). The tire is still losing pressure - I've taken it back to Sears and they can not find anything else. So then I took it to Lexus and they took apart the tire as well and found no leaks in the tire, the stem, the TPMS or anything else.

Any ideas on what it could be? Can the patch/plug still be leaking, even after Sears looked at it again?

 

Take it to a real tire store (Goodyear, etc...). They should find the leak. If the ambient temperature drops drastically, you will lose pressure also. I think it is 1 pound per 10 degrees.

 

So how sure are you if you are losing air? Have you been using a gage? How much air are you losing?

 

I have had valve issues, where it would seat it self right after a air pressure check.

Fill it up and if you think there is a leak, do not test the air pressure but have the valve tested for leak.

Salim

 

Suggest filling the tires with nitrogen. They say that nitrogen will not fluxulate like O2.

 

Check where the weights are. Mine was leaking slowly but enough to lose a few pounds every week. My local tire guy found it, sealed it all up and replaced with stick-on weights. Good luck.

 

At first I was in agreement with other posters and the temperature, but seeing you are from TX, it does not seem likely. The tire that is loosing air, can you be sure there are no bends on the inside of the rim. I had a similar situation that bothered me for awhile because I could never find the cause of air pressure loss. It seemed like almost 2 years it would intermittenly and very slowly loose air. Well, one day when the wheels were off Iwas looking at the back of one of the rims and there was a slight bend/damage where the tire seals up to the rim, nothing major,, but all I could think was if the vehicle was parked at that point it may have slowly lost pressure. Just a thought, check the rim out thoroughly on the wheel giving you trouble. Good luck,

 

+1 My parent's RX had a valve stem issue. Try putting some soapy water all over the stem including where the air goes in.

 

I purchased a set of 4 Cooper Zeon Sport A/S tires in 2008. No issues for the first year. However during the second year with 10,000 miles on the clock I began experiencing
major issues with air loss on 3 of the tires. The pressure would drop from the recommended 30 to 15 within a matter of days. They were never patched and there was no evidence of nail or puncture.
The shop removed the wheels and submerged them in a tank of water to check for leaks. Valve, stem as well as the bead were replaced 3 separate times. All to no avail, the tires still kept losing air.
I finally replaced with with Yokohama Prada Spec X tires. Very HAPPY and no more issues with air loss.

 

No, you will see absolutely no difference in leakage between nitrogen and regular air. Remember that the atmosphere is already 78% nitrogen. Lots of tire places are pushing nitrogen now as a gimmick to make extra money. There's nothing wrong with using pure nitrogen, but it won't improve your ride, it won't stop leaks, and you won't get better mileage.

Nitrogen is used in aircraft tires because the process to separate the nitrogen also removes the water vapor. Water vapor is bad when going from -30F temperatures at altitude with no load to supporting the weight of a plane at 150 mph upon landing. That's the only reason to use nitrogen.

 

^^ So true. Also keep in mind when the tire is put on the rim, it is full of air [not pure nitrogen]. It is impossible to evacuate the tire and remove air and then fill it with nitrogen. So the shops who advertise nitrogen are really providing compressed nitrogen to go from atmospheric pressure to 32psi or so.

The real advantage is that they fill it with nitrogen which does not have water. Ordinary compressors will just compress the moisture in the air [if their moisture filter is not working and in most cases is not present].

Salim

 

I notice that with the nitrogen I have never had to add to them, never. Plus they seem to ride smoother too. If nitrogen isn't better wonder why race car tires are filled with nitrogen??

 

NItrogen is used by racers because the expansion coefficient is less. It allows a more constant pressure in extreme temperatures. In racers a 1 lb difference in pressure matters. For the average car on the street it's worthless.

 

The only advantage in using nitrogen is that a nitrogen fill will keep pressure a bit longer than air.

 

Please dont misunderstand me ... No denying that pure nitrogen is superior than just compressed air.

A dry compressed air will get you almost there. The difference people note is due to moisture in the compressed air which changes form from liquid to gas and back to liquid.

Salim