I own an 89 F150, straight6 engine, 5-speed manual transmission, 2 wheel drive pickup truck, and lately it sounds like WWIII is being fought under the hood. There is a loud clattering sound which appears to be coming from the front of the engine, around the power steering pump (which is fine). The noise is rhythmic, in time with the engine, and speeds up when the engine is revved. It often (but not always) disappears when I depress the clutch pedal, and sometimes it stops for a while on its own. I have been told that it could be the harmonic balance damper, but the HB isn't even loose; I do know that the throwout bearing and the sleeve are shot; could that be what is making all the racket, and if so, why does the noise coincide with the rhythm of the engine? ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~Cj