Sympthoms of bad rings vs. bad valve seals

Discussion in 'Fox 5.0 Mustang Tech' started by Fastcat, Jul 8, 2004.

  1. Whats the sympthoms of having bad piston rings and bad valve seals? And how do you check to see which is bad w/o breaking the engine down?
  2. I think a compression test will tell you if you have a problem with the rings.
  3. you can do a compression test. The numbers you get really aren't as important as if they're all within 10% of each other. If you get low results (more than 10% diff. from highest psi) on a few cyclinders, you can throw some oil in there (not much, prob. a cap full?) through the spark plug hole. Re test...if compression goes up w/ oil added, then you know it's bad rings - the oil fills in the gaps left by the rings. You might search for info on a "leakdown test," which is a test where you input air into the cyclinder and see how much of it stays...I believe that's basically what you do, but it's supposed to be a better test because it has nothing to do w/ valves opening, etc.
  4. bad valve seals will blow blue smoke on startup,
    bad piston rings -pull out the dipstick when the car is running. see steam? pull off your cap and rotor and look into the distributer see burnt oil? put on a breather filter and see if there is TONS of oil steam coming out of it.

    just my experience
  5. just does steam out of the dipstick tube indicate bad rings? The tube goes to the oil pan, which is compeletely below the rings. Most likely, that steam is from oil burning off inside the tube.
  6. A typical symptom of bad valve seals/guides is you will notice oil/deposits built up on the side of the spark plug facing the intake valve. With worn rings, usually the entire tip of the plug will have oil/deposits on it.

    When you have worn compression rings part of the air/fuel mixture blows past the worn rings; the result is air/fuel that is supposed to be in the combustion chamber turns into "blow-by" and ends up in your engine's crankcase. Your dipstick tube goes into the pan and acts like a "vent" for the crankcase and allows the "blow-by" to escape; hence you see smoke comming out of the dipstick tube.

  7. the heat of the combustion goes past the rings and makes the oil burn under the pistons, which make blowby. so oil smoke will come out of the valve covers and dipstick. i have never seen oil steaming out of a dipstick tube with an engine with good rings before.
  8. I have also heard that on decelleration if you have bluish smoke out of the tail pipes that indicates worn valve seals