I took my valves out, cleaned and lapped them and put them back together. I also put new valve stem seals. At least on one side of my V6 Tacoma.

I performed several water tests to check the seal of valves on seats after lapping them. Had to successfully redo two valves and am down to one last dripping water, will do that next. All the three leaking valves were on the exhaust side (not sure if that's a coincidence or correlation).

I did the test by setting the engine block mating surface up and level and then filled the recession in each combustion chamber with water. Leave it 30 min to see if any of the three puddles has lost water and look into the ports to see each valve from inside for drippage.

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I saw this method in a YouTube video and was wondering how effective and authentic it is in verifying that the seal is tight.

2 Answers 2


I'm thinking it should work pretty well. I don't have any evidence to back up that statement, though.

There is another method you may want to try to confirm, though. All you need is a magic marker (or Sharpie)

  • Pull the valve out of the guide
  • Use the marker and mark the seat face (the angled part where the valve seats at) all the way around
  • Put the valve back into the guide so it is set upon the seat
  • While applying firm pressure against the valve face, rotate the valve about 15° at the most; rotate it back and for a couple of times, but no further than 15° total
  • Pull the valve back out and check the marker on the seat. If it is ringed all the way around, your seal should be good. If not, lap it some more. If it doesn't come out after a couple times of lapping, you'll need to get a valve job done.

Don't use water, use gas since it is less dense than water. Water can tell a gas tank is not leaking, when in reality it is when you put gas in it! I always use gas for checking valves...

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