I put metal valve caps on my tires a year or so ago, because I'm an idiot. When I went to add some air to my tires one day, I found that the caps were seized up. Now I am unable to get them off. This is a sensitive part, so I can't just muscle them off.

I have tried:

  1. Liquid wrench.

  2. Holding the stem with pliers and turning the cap with another pair of pliers. I used as much pressure as I was comfortable with and no joy.

I'm out of ideas, because brute force methods will lead to much bigger problems.

Any ideas of how I can get these off without causing further damage?


These are rubber stems, and luckily they don't have a pressure sensor (i hear that makes them extra fragile)

now I know why valve caps are plastic

  • 1
    Are these rubber stems or metal stems on a tire pressure monitor?
    – JPhi1618
    Commented Apr 28, 2016 at 19:29
  • 1
    Plastic valve caps are around because they are cheap. Chrome plated brass valve stem covers are fine and do not corrode on a brass valve stem, but they cannot be used on an aluminum stem or they will seize.
    – JPhi1618
    Commented Apr 28, 2016 at 19:38
  • "now I know why valve caps are plactic" did you mean plutonic? he he
    – Moab
    Commented Apr 28, 2016 at 22:42
  • Very likely to galling of aluminum . Aluminum is very prone to galling which is many microscopic welds. Lubrication will not help once it is galled. Very unlikely to be steel rust , unless the wheels are exposed to salt water. Commented Aug 6, 2018 at 0:29

8 Answers 8


Fellow idiot here.

Penetrants won't work. Get a hacksaw with a very fine metal blade and saw away. Use a screw driver to pry open both sides when you have enough clearance. You need to cut the top and one of the sides.

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  • Took nearly an hour to cut through the top but a junior hand held hacksaw blade worked for me. Wasn't confident enough to use the Dremel. Only took a couple of strokes to expose the thread. This was alloy/whatever to brass and had left a white deposit on both threads which I guess was locking it. The other three were quite clean, but now taken all the metal ones off and replaced on all my vehicles with plastic. Thanks for the tip.
    – Ken Foster
    Commented May 29, 2019 at 13:45

Given that it sounds like they have rusted to the valve stems, you could try soaking the threads and the whole area with PB Blaster specifically. I have seen it work really well, and could be better than Liquid Wrench. Although that does work well too. And when I say soak I mean overnight. It's not like you can use heat to loosen them up, you'll melt the valve stem.

If they still won't come lose, you can always take it to a tire shop and replace the valve stems with nice plastic caps.

Trust me, if this is the worst thing you ever do to your car, you're doing just fine. Lesson learned, we've all done worse I have no doubt.

  • i.sstatic.net/w522C.jpg - Hacksaw does the job cheers heaps fellow idiot hear your a life saver tried everything then came across this. Commented Nov 15, 2017 at 15:54

If using some sort of penetrant doesn't help loosen up the caps, you can cut them down the side with a Dremel tool. You will mess up the threads on the valve stem a little, but they will replace the stems when you get new tires anyway, so its not a big deal.

I would cut down one side, being careful not to go too deep, then try to pry the cap open by twisting a flathead screwdriver in the new channel that you just cut. The cap should be brass or aluminum, so it will cut quick and easy. Note that the valve stem is also brass and will cut easily, so be careful and don't try this if it's your first foray into dremeling.

  • This was gong to my last ditch effort, but it seemed a little extreme. But I guess if I nick the threads, I could still get a plastic cap on.
    – Dan
    Commented Apr 28, 2016 at 21:01
  • 1
    Yea, if you had a TPMS or alloy wheels with metal stems I wouldn't recommend this, but I wouldn't even consider it extreme on the disposable rubber ones. The cap is really just for dust so it's no like the threads have a super important job.
    – JPhi1618
    Commented Apr 28, 2016 at 21:03
  • If the caps are made of soft metal you may be able to drmel most of the way through then split them open with a screwdriver in the dremelled slot. This would save the valve threads (or see @jsn's answer).
    – Chris H
    Commented Apr 29, 2016 at 9:01

Drill a hole in the top of the cap and squirt your favorite rust eater in there, this way you can soak it from both sides of the thread.

Also some gentle heat will draw the lube into the threads.


I'd combine the answers from @Jphi1618 and @Jsn - use a Dremel or similar to cut almost all the way through - up one side, across the top and back down the other side. You can then use a screwdriver or a nut splitter to split the cap in half - hopefully without having to cut far enough to ruin the threads on the stem.

Some damage to the threads will be fine, and most of the time you don't really need caps anyway, unless you're driving through mud or in a really dusty environment...


Use a dremel to grind off the top of the cap but do not go to deep and hit the threads on the valve stem. Then use a fine hacksaw blade ( just use the blade only and hold with your hands ) to make a cut from top to bottom of the cap . Do not go to deep and cut the thread on the valve stem. Then use a small flat screwdriver to pry cap apart it is just soft metal.


It's actually quite easy . Once you realize never to use those aluminium caps ever again. All I did was use a pair of vice grips to hold the valve stem in place. Wear a pair of gloves and then use your shortie hacksaw hand-held blade to slowly get it started. On the flat end piece. Cut a groove for a flathead screw driver. Then cut carefully down the side of cap to lightly expose and only until you see the thread of the valve copper. Then simply keep vice grip in place to allow yourself to use flat head to break the corrosion bead. And your good.


I used a Dremel on 1 of them, it took only 2 minutes to cut it just enough on top and on 1 side for it to crack. As somebody else mentioned, don't cut it deep and you will not damage the valve. I wasted $40 each on the other 2 tires where the the valve had to be replaced. I feel so stupid.

  • You are not alone - went to change a ball joint ($20) and it was seized - messed up the track rod which was $150..... Oh those cheap jobs...
    – Solar Mike
    Commented Jun 16, 2017 at 20:12

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