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Whirring noise on long highway trips

2007 Chrysler Town & Country, 72k. It’s happened twice now. On long interstate trips, over 50 miles, the engine starts to make a loud whirring/humming sound. The temp and RPM gauge looks fine. The first time it happened, I checked the dipstick and it was very low (I was overdue for an oil change). I topped it off and it went away for a few weeks but then it came back, after about 100 miles running it 75 mph or so. Then the oil was fine. Pulled off and let it cool for 30 minutes and it was fine but I drove slower. It seems to come on while I’m on the interstate and the engine noise covers it until I get off and then it’s very loud. Maybe it seems to get louder when I take my foot off the gas. Any ideas?

Next time it happens, roll up a piece of paper into a tube, slightly horn shaped and stick the small end in your ear. Point the open end toward various parts of your engine to see if you can locate the source of the noise. Don’t stick you head down into the engine area, that is too dangerous.

Chances are the noise is made by one of your accessories, like the power steering pump or the alternator. BTW, have you checked the fluid level in the power steering pump?

Yeah, power steering fluid is fine. The power steering seemed fine as well. If it’s worth anything, the alignment pulls a hair to the left, getting that fixed soon.

Check your cvs as well

Pick up a "mechanic’s stethescope (about $10) at the local parts store. Touch the end to various components as the engine operates and see if you can hear the noise. The stethescope has a diaphragm that magnifies the noise, and you’ll recognize the noise when you touch the correct component. Hint: old alternators often make whirring noises that vary in magnitude.