Does this resemble a metallic ticking? Does it sound light and faint? Or deep and heavy? If you say it sounds like it is coming from the oil pan area, that is usually indicative of a rod knock, if it sounds like it is coming from the middle of the engine and gets louder on acceleration, that is indicative of piston pin play, the difference is a rod knock usually will result in catastrophic failure very quickly, where as a piston pin can keep going indefinitely, if you change your oil to a heavier viscosity and notice an immediate difference in the sound you will know it is an internal mechanical noise, sometimes with wrist pin noise increasing the oil viscosity will virtually eliminate the noise, and at 143000 miles it isn't a bad idea to do anyway, if you were running 5w30, per se than increase to 10w40. If it is a rod, you will notice it gradually get louder before it fails. Ticking can also come from the valvetrain, a stuck lifter can also cause the engine to idle poorly, but you really want to be able to decipher where the sound is coming from, if you have a mechanic's stethoscope or a long screwdriver you can touch it to the suspected area (engine running) and put your ear to it with your earlobe closed and you will be able to hear if it is a metallic sound and where it is coming from.
Tuesday, May 19th, 2015 AT 3:57 PM