I'm still amazed at the number of supposed "mechanically inclined" that look at me like a nut when I ask if they've used their mechanics stethoscope to diagnose an engine or drive-line noise.
A mechanics stethoscope is just that. Look like the one the doctors use except the listening end is typically a removeable metal rod. You place the rod on the body near a suspected noise source and listen. Got a squeal or whine? You can check for possible rough or bad bearings by putting the probe on the item, such as water pump or alternator, and listening for differences. Same of wheel bearings or driveline.
Cheap -- maybe $10-15 -- at most of the auto parts and tool stores. By the way, this is similar to some of the old-timers trick of putting a screwdriver near a bearing and listing with the end. They are not crazy, the screwdriver helps carry the sound or vibration.
Last edited by Capt. Mike; 12-27-2008 at 05:01 PM.
The mechanic's stethoscope can also be used in the increasingly popular Leak-down Test. Most allow removal of the metal probe and leave an open ended hose with direct route to the ears. This can reach into small areas like the dipstick, coolant tank or intake so as to listen for the tell-tale leak sound. It's this leak that helps diagnose the probelm area during a leak-down test.
Your earpieces help block extraneous sound and the probe hose can direct desired sound and isolate others better than trying to get your ear close enough.