Looking for advice of how to track down either a squeal or whistle from the engine bay.
If I take the 03 TJ (4L Straight-6) out and drive under 20 mph in the neighborhood, no problem. I off-roaded yesterday for a few hours at slow speeds and heard absolutely nothing. As soon as I get up to about 35 mph, if I start to coast I hear either a squeal or whistle from the engine bay once I idle down to 1500 rpms. I can make the noise go away by revving the engine back to 2000 rpms. I can also "control" the whistle in sound/tone, by hitting the gas and letting off.
The noise continues for 30-60 seconds if I come to a complete stop at a light. If I turn off the engine it stops. If I park the Jeep, within 30-60 seconds the noise will stop. I can't seem to get the noise to happen or remain by revving the engine in neutral. The fact that I have to get the Jeep onto a road at higher speeds and then pull over, unlatch the hood, and try to diagnose within 30 seconds is making it impossible to find.
I first focused on the belt driven accessories. I replaced the original idler pulley, the tensioner (and pulley), and the belt. I sprayed water on the belt after pulling over during the sound and it didn't seem to make it go away any faster than the normal 30-60 seconds. I used an automotive stethoscope to see if I could find the problem on the pulleys and couldn't before the noise goes away. I was able to check the alternator and replaced pulleys. I wasn't able to figure out how to get the stethoscope to the fan clutch or lower pulleys (AC, power steering, crank, water pump).
My garage is thinking that this might be a vacuum hose leak based on it sounding like a whistle to them and not a squeal, but they couldn't confirm as the noise stopped after 30 seconds of showing up there. I have read about pinching and using sprays to pinpoint hose leaks, but again, this would mean I'd have to get the sound reproducing for a longer period of time.
If you think based on the description that you'd know what it is that is great and let me know.
However, I'm mostly wondering if there is a trick I don't know of to keep the engine going in such a way that I can hear the sound for a longer period of time to track it down.
If I take the 03 TJ (4L Straight-6) out and drive under 20 mph in the neighborhood, no problem. I off-roaded yesterday for a few hours at slow speeds and heard absolutely nothing. As soon as I get up to about 35 mph, if I start to coast I hear either a squeal or whistle from the engine bay once I idle down to 1500 rpms. I can make the noise go away by revving the engine back to 2000 rpms. I can also "control" the whistle in sound/tone, by hitting the gas and letting off.
The noise continues for 30-60 seconds if I come to a complete stop at a light. If I turn off the engine it stops. If I park the Jeep, within 30-60 seconds the noise will stop. I can't seem to get the noise to happen or remain by revving the engine in neutral. The fact that I have to get the Jeep onto a road at higher speeds and then pull over, unlatch the hood, and try to diagnose within 30 seconds is making it impossible to find.
I first focused on the belt driven accessories. I replaced the original idler pulley, the tensioner (and pulley), and the belt. I sprayed water on the belt after pulling over during the sound and it didn't seem to make it go away any faster than the normal 30-60 seconds. I used an automotive stethoscope to see if I could find the problem on the pulleys and couldn't before the noise goes away. I was able to check the alternator and replaced pulleys. I wasn't able to figure out how to get the stethoscope to the fan clutch or lower pulleys (AC, power steering, crank, water pump).
My garage is thinking that this might be a vacuum hose leak based on it sounding like a whistle to them and not a squeal, but they couldn't confirm as the noise stopped after 30 seconds of showing up there. I have read about pinching and using sprays to pinpoint hose leaks, but again, this would mean I'd have to get the sound reproducing for a longer period of time.
If you think based on the description that you'd know what it is that is great and let me know.
However, I'm mostly wondering if there is a trick I don't know of to keep the engine going in such a way that I can hear the sound for a longer period of time to track it down.
