How to Check Piston Rings

The piston rings are an important part of your car’s engine, sealing off the pistons in the combustion chamber and preventing any energy from escaping during compression strokes. Three rings come with each piston. There is an expansion ring, a compression one and a thick oil ring. These work with a piston by riding up and down the cylinder with it. They need to maintain an almost perfect seal under extreme heat and moisture and in some cases, polluted oil. They are small and delicate parts, but they have a very important task. Diagnosing problems related to the piston rings is often not so difficult, and sometimes it can help you save a lot of cash.

Tools and Materials Needed:

  • Spark Plug Wrench
  • Feeler Gauge
  • Magnifying Glass
  • Motor Oil
  • Compression Tester
  • Socket Wrench

Step 1 – Listen for Strange Noises

If you find that there are any unusual noises originating from the sides of the engine or beneath the vehicle or by the oil pan, then you may have a problem related to the piston rings. Connecting rods and bearings will often make knocking noises, although if you hear a hollow, bell-like sound, this normally points to a problem with the piston rings. In this case, it means that the piston is riding with too much side-play within the cylinder wall. This condition is often caused by worn rings.

Step 2 – Look for Bluish Smoke

If there is any bluish white smoke occasionally coming from the exhaust pipe, this could be due to damaged piston rings. Although oil burns with this color, you should not see bluish white smoke coming out from the exhaust pipe.

Step 3 – Remove High Tension Wire from the Engine

Unhook the wire from the engine, removing any spark plugs as well. Have somebody help you by cranking the engine a few times as you monitor each cylinder using a compression tester. Write down the pounds per square inch recorded for each cylinder. Place a small cap of oil to each of the cylinders and then test the car again. Compare these numbers and write them down. If the pressure is higher than thirty pounds per square inch in any of the cylinders more than it was before, then you will need to replace the piston rings.

Step 4 – Examine the Rings Themselves

You can use a magnifying glass to inspect the rings when you have removed the pistons from the engine. If there is any discoloration on the end of the ring’s outer surface or the bottom side, then they will probably need replacing. They should be shiny in these areas. You should also examine the rings for lines, grooves or scratches or any other distortions. Contaminated oil can also cause problems. Use the feeler gauge to measure the gaps of the rings when they are fully open. You should also consult the owner’s manual of your car to determine the exact correct thickness of the gaps. Finally, you should also examine the rings for consistent thickness. There should not be any variations from one end of them to the other.