TMPS Detectives:
We recently purchased a used certified Lexus from a well know Lexus dealer. The dealer stated they replaced the tires and it also is stated they did so on the service records. After cleaning the car, I checked the pressure in the tires and noticed several items not so kosher with the TPMS configuration. Less than 100 miles put on the car since the tires have been replaced.

Here are the photos. Can you spot the questionable workmanship?

 

TPMS valves should have silver valve cores - brass valve cores can have a galvanic corrosion with the aluminum valve stem which can cause them to not ever be removable thus ruining a $150 sensor...

also, TPMS valve stems should have either a plastic valve cap or approved thin metal valve cap (that is not a thin metal valve cap)

on top of that, I would say that the sensors were never removed when the tires were replaced... it is SOP to remove the sensor completely and replace the grommet, ferrule nut, valve core and cap...

 

You got it exactly. However the OEM caps are thick Aluminum on this model.
I believe that is the only cap on this car that is correct. The others are thick steal or plastic. They must have a special tire changer if they did not remove the sensors before removing the tire. I thought the sensor would be damaged/broken if they were not removed. I thought they removed it and reused the old grommets. In either case they did not rebuild the grommets and valve core as can be seen by the corrosion on the grommet nuts and value core. Out of the four cores, two have brass inserts. The one new brass valve core indicates they purposely used the wrong valve core type. There will be a call tomorrow and will be interesting how they will handle this.

Do they have to remove the tire from the rim or just break down the tire bead to rebuild? In the first photo, you can see the corrosion building up already.

Here is a photo with a bad cap..

 

You can actually change tires without removing the sensor if you know what you are doing on any tire changer, it just takes a little more care... Many people don't know or care about the valve core - however, it can be a costly mistake down the road...

Two ways to rebuild the sensor - 1) use a tire machine with a helper arm to push down the bead or 2) dismount the top bead completely or remove tire and reinstall...

On low profile tires like those it is much less hassle to just remove the tire completely

the tire change process for those is just a little different than normal valves... the main steps changed are: after deflating the tire, remove the ferrule nut on the sensor and allow the sensor to drop into the tire, then remove tire and then on installation there are two ways to do it - 1 is to have a handle with small chain on it that attaches to top of sensor like a valve cap does - mount the tire while this is hanging on to the valve inside the tire, then once mounted, pull to seat the valve in place, or the alternative is to mount the tire, then use the tire machines helper arm to push the tire down to gain access to the valve hole...

on low profile tires like yours, I cheated and reinstalled the sensor first, leaving it a little loose... then, so long as you are careful, you remount the tire, then tighten the ferrule nut...

two more tips on TPMS systems... the ferrule nuts should be tightened to 18 ft pounds I believe - please double check this as I do not remember completely, and it can vary between manufacturer... also, the valve cores should be installed with a valve core torque wrench as well... basically a fat valve core tool that will not allow them to be overtightened...

 

Dealer took care of the issue up and beyond. Great service.

 

ok, so are you saying that if something is wrong with that internal pin, (that you use to let our air or whatever) you can get that whole section replaced easy and cheap? because I got new tires put on and was told two of my sensors were bad, when you look at them, the pin is either broken or gone. I bought two used ones from ebay and they were the same way. so, can the internals of these things be repaired or not? seems like the only expensive part is the transmitter part.
thanks

 

Yes you can replace just the valve core and grommets, we recommend TPMS fit kits that we sell for like 3-5 each.

 

This is a very informative and great post actually, I am going to sticky this.

 

This is a GREAT post. Another thing that Tire techs take into consideration is whether the wheel is face up or face down mount. Most Factory wheels are face up (the face of the wheel faces up on the mounting machine). Its when you get into fatter lips and 3 Piece wheels that things start going upside down. I have personally broke one of those sensors (a good 135.00 from my paycheck to local BMW dealer). Care should definately be taken when seating and/or breaking the bead and yes 18lbs is correct.