Roundel Metal Valve Stem Caps vs. Plastic
03-25-2008, 12:02 PM
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Several owners have told me their SA told them on the newer cars if your valve stems are black you can use the metal valve stem caps, yet if they are grey then you have to use plastic caps. The reason being they have changed the tire pressure monitoring on cars with grey valve stems and the metal caps would cause faulty readings. Something to do with the pressure readings reflecting back off the caps. However I checked my valve stems and they are grey and I have the metal Roundel caps on them... with no issues. Go figure. 
Anyone else heard of know of this isuue?
Anyone else heard of know of this isuue?
03-25-2008, 12:21 PM
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The issue has nothing to do with faulty pressure readings. The grey valve stems used with the TPMS sensors are made of aluminum. The metal caps will react with the aluminum, corrode, and get stuck on the stems.
03-26-2008, 02:10 AM
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Originally Posted by iversonm' post='550567' date='Mar 25 2008, 03:21 PM
The issue has nothing to do with faulty pressure readings. The grey valve stems used with the TPMS sensors are made of aluminum. The metal caps will react with the aluminum, corrode, and get stuck on the stems.
Would be interested in knowing where you got that information. I would like to educate the two SA that told me it had to do with the computerized pressure monitoring system.
03-26-2008, 03:20 AM
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Originally Posted by TX Buzzard' post='550948' date='Mar 26 2008, 06:10 AM
Would be interested in knowing where you got that information. I would like to educate the two SA that told me it had to do with the computerized pressure monitoring system.
This article alludes to the corrosion problem, but specifically references the valve body, rather than the screw on cap. This article alludes to both the corrosion issue and another issue closer to what your SA references. Here's one more link as well.
03-26-2008, 03:55 AM
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For some reason, I feel compelled to ask the question: "What have we come to...when our cars take issue with which valve stem cap we use..." 
03-26-2008, 04:02 AM
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Originally Posted by Allen' post='550960' date='Mar 26 2008, 07:55 AM
For some reason, I feel compelled to ask the question: "What have we come to...when our cars take issue with which valve stem cap we use..."
Shhhhhhhhhhhhh!!!!! Don't speak badly of the cars. They monitor the forums.
03-26-2008, 05:02 AM
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Originally Posted by iversonm' post='550952' date='Mar 26 2008, 06:20 AM
Researching this further, it appears that both your SA and I am correct. Corrosion is a problem with the aluminum stem. However, a metal cap can interfere with the sensors ability to transmit. It appears that the valve stem acts as an antenna for the radio signal.
This article alludes to the corrosion problem, but specifically references the valve body, rather than the screw on cap. This article alludes to both the corrosion issue and another issue closer to what your SA references. Here's one more link as well.
This article alludes to the corrosion problem, but specifically references the valve body, rather than the screw on cap. This article alludes to both the corrosion issue and another issue closer to what your SA references. Here's one more link as well.
(And, no, that's not the purpose of a head gasket.)
03-26-2008, 05:48 AM
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Originally Posted by GT Premi' post='550972' date='Mar 26 2008, 09:02 AM
I'm glad you did some research, otherwise I would've been compelled to ask you how you suppose manufacturers can get away with using iron blocks and aluminum heads on their engines. (And, no, that's not the purpose of a head gasket.)
(And, no, that's not the purpose of a head gasket.)At least the E60 as aluminum hubs.
03-29-2008, 05:16 AM
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Originally Posted by iversonm' post='550952' date='Mar 26 2008, 06:20 AM
Researching this further, it appears that both your SA and I am correct. Corrosion is a problem with the aluminum stem. However, a metal cap can interfere with the sensors ability to transmit. It appears that the valve stem acts as an antenna for the radio signal.
This article alludes to the corrosion problem, but specifically references the valve body, rather than the screw on cap. This article alludes to both the corrosion issue and another issue closer to what your SA references. Here's one more link as well.
This article alludes to the corrosion problem, but specifically references the valve body, rather than the screw on cap. This article alludes to both the corrosion issue and another issue closer to what your SA references. Here's one more link as well.
Wow. Very good information! Thanks.
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