wolfepack88

I took my car in for its first A service and my tires had the Mercedes metal valve caps on them from my 211. My dealer gave them to me as a freebie when I leased my 211. When I got the 212 I moved them on to the wheels. Apparently Mercedes has found that the tire valves can swell and the metal valve caps don't give and they can actually become stuck. This happened to my right front tire and the valve literally broke trying to remove it. They had to replace the valve and tire sensor the whole deal. They covered it but warned me never to use metal valve caps again. Funny thing is they still sell them in their parts department. Had they not covered that it would have been very expensive to repair.

sosh

I was warned about that when I took delivery of my W212 and my ML550. In addition to the problem you experienced they can also interfere with the signal for the tire pressures. I also believe this is stated somewhere in the manual.

RickP330

I had this problem on my W204 - even though I was sure not to over tighten them - I nearly destroyed one getting it off - worse yet was I on the road and couldn't fill the tire. I use anti-sieze (very little!) and it's a non issue now, but you can't even think of tightening them!
RP

Dema

You mean if you turn leased car, you can keep the caps. It is cool, I didn't know. I need to check lease turn car guide to see what items can be removed from car without being charged.

mm9351

Is this problem unique to MB, or other auto mfrs as well? I have metal caps on my Passat (also with tire pressure monitors) and had no issues. Thanks for your thoughts / replies.

sosh

From what I have been told this issue seems to be applicable to all of these stems.

RedG

Brass alloys are used for valve stems because they typically won't be subject to severe corrosion issues. As such that is why the typical 'metal' caps are brass alloys also. This becomes problematic when used on aluminum tire pressure sensors. They (brass metal caps) through the process of metal bonding corrode or 'weld' themselves on the aluminum sensor. This is common of ANY manufacturer when these circumstances are met.

Though I have seen this problem with aluminum caps too. They have allowed for excessive corrosion to develop between the cap and the sensor also causing this problem. Your best bet is to simply use plastic caps at all times UNLESS you have the traditional brass pressure valves.

sosh

Do not know what metal the MB caps are. Could be stainless or a chromed steel. However none of these should be used on the TPMS valve stems. I was told that they also can interfere with the TPMS signals. I used to use Dill stainless caps and have a box that must have 900 left that i have had for years and now I can't use them on either of my daily drivers.

sy1616

very true, I had three of four gall on me, it's an AL to SS issue,

Dema

Previous generation of E350 has also TPMS and metal caps.