Testing piston ring

Question

One of my cylinders is leaking and I have determined so far that at least one or both of the intake valves are leaking. However, now that I have that cylinder head off, I would also like to test the piston ring. Can I pour water in the combustion cavity when the cylinder is in bottom dead center and see if it loses water, catching it under the lower oil pan where I normally drain oil on change? I can such the leftover water (hopefully all of it) out of the combustion chamber using a syringe.

Answer 1

Basically, no. You're going to lose fluid past the rings no matter what, plus, how are you going to measure this anyways? This isn't how you test your piston rings.

The way to test your piston rings is two fold. First, you can check for blow-by. This isn't a quantitative test (or there's no real way to quantify blow-by). You can look to see, while the engine is running to see how much blow by is making it up through the crankcase. If you see it increasing, you know there's an issue with your piston rings not controlling the combustion gasses.

Secondarily, you can do a compression test. This is a quantitative test. Every production engine will have a specification for compression. As long as you do the test correctly, you're going to be able to check compression two ways. First, check it against what the standard is. Secondly, you check each cylinder against the others. There should be very little variance between cylinders (ie: all should be within say 10% of each other).

Both of these things can only be done with a complete put-together engine. You don't check your rings with the heads off.