S80: Wheels/Brakes TPMS Stem galvanic corrosion.

[ShadeTek]

I have been meaning to put some air in my tyres for a few weeks now so at lunchtime I decided to go out and try it. I have Volvo built in TPMS but also I fitted my own aftermarket valve cap stem top sensors which are better than the Volvo system as they give a PSI readout, temparature readout and all with upper and lower limit alarms with rapid deflate alarm. I have had some minor trouble in the past removing the cap locking ring but today was especially bad since I have not had them off for about a year. Big mistake. I could not get enough force on them to remove the ring which retains the caps on. When I did, the whole alloy stem sheared off and rapidly deflated the tyre. The compressor and gunk supplied by Volvo to rectify this would have been useless. I had heard of horror stories of people being stranded with no spare wheel so that was one of the first things I bought when I got this car. Replacement valve stem from Volvo £23. Replacement valve stems from eBay for FOUR for £15. The need was great so I ordered one from Volvo. However I sense the same happening to the remaining 3.

I am soaking them in penetrating oil for a few days then hold the brass lock ring with mole grips in the hope it squishes them enough to leave a minute gap to let the fluid seep in to the threads. Galvanic corrosion is a huge problem for TPMS stems and why contructed using alloy? Lots of threads on the subject if you care to investigate.

[Paul Wildsmith]

yes, I had exactly that on my S80 (I'd retrofitted the Volvo TPMS). Fortunately I had a spare wheel. Tyre centres have these valves available now, can't remember how much, around £10 or £15 from memory. No need to buy Volvo. If I still had the car, my plan was to replace them every two tyre refits over tht years.

My current S90 doesn't have these valves (the TPMS done by speed comparison).

[pelagicskipper]

I use copper grease on the threads.

[Bashy]

Thats the problem with these cheapo aftermarket sensors, the locking ring seizes on and its the same on them all on amazon, just read the reviews. I am sure some have swapped the ring for another type with some success.
I read that its an anti theft feature? if so, wouldnt it be cheaper to leave the ring off and just replace them if stolen compared to the damage and time wasted?

I really want to have TPMS again, its one of the few features i miss from the Laguna, but its this corrosion thats put me off them, i quite like the android app version

[ShadeTek]

It would be interesting to know if the onboard Volvo TPMS sensors transmitted temperature information and that they could also be linked to an aftermarket sensor.

[ShadeTek]

Here is my fix to reduce corrosion in the future. Use a plastic nut instead of a brass one, not installed yet in the picture, put a rubber o-ring between the plastic locking nut and the TPMS valve and tighten but not too much. Cover in grease or silicon to keep any road salt off.