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Tire Pressure Loss

edited October 2011 in General Discussion
I have read many of the comments re tire pressure loss but don't know if I have a unique problem or not. I own a 2011 GMC Terrain and my tire pressure is monitored through On Star. Every report I receive tells me my pressure is low in all tires - about the same amount, with little variance. Fortunately I own a air compressor and add air - virtually every 10 days or so.
The dealer tells me all tires have small pores which cause leaks and I should go to a tire firm to have nitrogen put in the tires. (He didn't say it would seal the tires but indicated it would solve my problem?) Almost all of the comments on your site do not speak favorably of this.
Any thoughts?


  • Tires do leak air...but no where near the degree you're seeing it. It might drop a pound or 2 every other month.

    What could also be happening is the temperature. This time of year temps are dropping...You fill the tires with air at 70....when it's 40 degrees...the air pressure will have dropped 3 lbs.
  • Thnx; that was one of the comments from a client in the waiting room when we discussed our problems. In Texas, it has been extreemly hot, so it would seem that the tires should be gaining psi, but not the case. Nonetheless, will continue to moniter.
  • I would also suggest the low tech approach and check them periodically with a good old fashioned dial type tire pressure gauge. This will rule out any issues relating to sensors and communication within your vehicle and to your email inbox (if that is how OnStar is telling you your tires are low). If your tires are still losing a significant amount of air, they may need to be separated from the rims, the rims cleaned, and bead sealer used with the reinstallation. Alloy wheels will often corrode where the tire seats to the rim, and this corrosion can create a breach through which air can leak. Steel wheels can do this too, but it is much more common on alloy wheels.
  • I agree with mark about checking the tire pressure on a regular basis with a dial-type tire pressure gauge. However, on a 2011 vehicle, it is very unlikely that corrosion of the wheel rims is an issue. On the other hand, vandalism is a possibility.

    Has the OP considered the possibility that somebody is screwing with him by regularly deflating his tires?
  • Mark9207 & VDCdriver; thnx for your input. To be honest, I seldom checked my tires on a regular basis and I did not have On Star to alert me. I previously had an 2003 Envoy, which I gave to my son and wish I had it back - if for not other reasons- the rear window was separate and able to be lifted without opening the door; and, my golf clubs could be loaded without having to lower the seat backs of the second row since they would not fit crosswise.
    Thnx to both of you.
  • This is not normal. You have leaks. Nitrogen will do nothing here. If you spray soapy water over the tires (especially the bead area and the valve area), you'll probably find them.

    Electronic gauges aren't always that accurate. You should get a good dial-type gauge (such as Accu-Gage) and use it regularly. The electronic system should just be a backup that alerts you to a major pressure loss.
  • There were bad batches of valve stems made in an Oriental country. Any respectable shop should be able to tell you where the problem lies.
  • Waterboy

    Those defective Chinese-made Dill-brand valve stems were made...probably about 5 years ago. I doubt that a 2011 model has these valve stems--unless of course our friends in China are up to their usual poor-quality manufacturing practices.
  • edited October 2011
    I still suspect valve stems as the likely problem. The nitrogen suggestion by the dealer is somewhere between idiotic and moronic. Air is almost 80% nitrogen.

    Valve stems are an inexpensive fix. Buy 4 stems and an extractor tool at a local car parts store. You must have a compressor to fill the tires, though. While you could pay someone to do this for you, it will cost a lot more than the 4 stems, the extractor tool, and the 120V compressor will. And then you will be able to fill your tires with air any Saturday morning you wish to. One more thing: you need a tire pressure gauge. You can get a great dial gauge at Sears for less than $10.
  • I'm thinking the problem is the gauge being used. What should happen is that the pressure is set above the "alert pressure", and then the tire (and wheel and valve) will leak down at worse at 1 psi a month. In theory, the alert pressure is many months of leakage lower than the placard pressure (You know about the placard, right?).

    You should also be aware that outside temperature will affect this. For every 10°F chnge, the pressure will drop 1 psi. This time of year, it's possible to lose enough pressure overnight to trigger an alert.

    Plus it is possible that the wheels are leaky - not at the tire/wheel interface, but through the alloy it elf.

    Lastly, you probably ought to take the vehicle back to the dealer and have them check on this.
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