TPMS Gotcha (or How I Dropped $165 on a New TPMS Sensor)
 

I noticed awhile back that one tire was missing the cap from the valve stem. No big deal, right? Someday I'll go to WalMart and buy some new caps.

Fast forward to yesterday when I went to Costco to get new tires. I'm told that the tire pressure monitoring sensor (TPMS) core is corroded due to exposure to moisture. When they deflated the old tire, the corroded TPMS core broke and it will no longer hold air. I had to run to the dealer to pick up a new TPMS for $165.

Lesson: You must keep caps on the TPMS valve stems AND they must be plastic AND they must be special caps with a moisture-sealing gasket inside. Metal caps will bind to the metal stems and break the TPMS when forcibly removed. Ordinary plastic caps may not have the gasket.

While educating myself on the perils of TMPS, I also learned that they have batteries to transmit the low warning signals to a receiver. The batteries last 5-7 years. Batteries cannot be replaced. You have to replace the entire sensor at $165 each when the batteries die. Plus the cost of dismounting the tire, replacing the sensor, mounting the tire and rebalancing the wheel. So there are recommendations to replace all four sensors when you get new tires at the 5-6 year mark. That will be one expensive set of new tires.

And TPMS is mandated by the U.S. government for all 2008 and later models. So even owners of low-end models will be saddled with these ticking time bombs.

Look, I know low pressure in your tires will cause problems and safety hazards. But I'm diligent about keeping my tires inflated and even adding air when the weather gets cold. (10 degree drop in temps = about 1 psi drop. PV=NRT for those who remember high school chemistry class. Pressure is proportional to temperature.) I suspect most people on this board are similarly diligent. But we must ALL be saddled with this expensive and failure-prone technology to protect us from ourselves.

And then nobody tells us about the pitfalls of the TPMS and how to properly care for these fussy and fragile little things.

We can all thank the Ford Explorer/Firestone tire combination for it.

"Ticking time bomb" is a bit of an overreaction, however.

Is your motor oil a "ticking time bomb" because it's going to have to be replaced?

Are your tires a "ticking time bomb" because they'll need replacement?

Lots of us apparently want our government to make life "nice" for us, and there's simply a cost.

PS: Should a sensor fail not due to owner neglect--which failure to replace a missing cap is--I'd bet it's covered by warranty. Little tough to "collect," I suspect, if work isn't done at the dealer.

All in all a pretty informative post.

There is an expectation that oil and tires will need periodic replacements. Drivers know this up front and they budget for these periodic services.

I think most owners of 5-6 year old cars will be rudely surprised when they have to spend over 600 bucks for a set of tire pressure monitors. Or the surprise will come sooner when they need a new set of tires and the sensors need replacing due to corrosion. Hence, the time bomb comment. Everything is fine...then SURPRISE! Fork over $600 or more if you want your new tires to hold air!

Wow, I certainly hope the metal valve stem covers sold to me by Mercedes for my GL don't cause corrosion in my TPMS, requiring me to replace the TPMS system(s) before 5-7 years! And nobody at Discount Tire, who are - I believe - familiar with TPMS, has told me they need to be plastic with a gasket either.

Is there someplace we can see these instructions printed for our benefit?

Thanks,

STP

When I had my wheels chromed I was only charged for 4 repair kits at about $25 each sensor.

Yes there is.

WIS document AR40.15-P-0080GZ, Remove/install wheel sensor, contains:

This document is on the W164 Service CD and can also be viewed with a subscription at http://www.startekinfo.com

That's right--the process on installing these things is very critical and there is no reuse of some parts.

Too bad about chroming your wheels--a process prohibited by Mercedes for safety reasons.

I did not know that MB changed their TPMS from using wheel speed sensor to inside tire sensors.

Thanks for the info, I do remember the dealer charging me for a TPMS when replacing one rim. They told me it wasn't a good idea to remove and reinstall it. The rim was $400+ so I wasn't too surprise to hear the TPMS was $100+ and just said whatever.

Do you know if they sell just the caps? I may want to just replace them every year since I know the gaskets maybe cracked from the weather exposure.

Yes, there's a part number for the caps.

Your dealer may have to buy 100 in order to sell you four.

Ouch that's a heavy hit. Next time check out http://www.titantpms.com/ you can get a full set of 4 for less that that. The Titan sensors are made by the OEM manufacturer and they also sell HUF sensors too for a lower cost.

Or just get a an entire set for $54:

https://www.ebay.com/itm/4-NEW-OEM-O...5Wl4et&vxp=mtr

I bought these for my Cadillac. Worked perfectly. The kid changing the tires threw 'em on, said theyre easy to install.