Posted by Eric [72.34.128.250] on Friday, February 28, 2014 at 17:25:46 :
I've got a 1970 W300 with a factory 383, no upgrades to the motor. My motor, or something under the hood, makes a high pitch whistling noise on occasion. When I am driving on the freeway, or at a steady RPM for awhile, then let off the gas, the whistle noise starts. And not like slowly gets louder, it just turns on, and loud! This noise continues, even when back at idle and changes in pitch based on whether the motor is under load or accelerating, being loudest when letting off the gas with back pressure. Eventually it will stop if kept at a idle or under very light load for awhile, but starts right back up when significant back pressure (down-shifting) occurs. I popped the hood and tried to figure out where it's coming from, but it's so loud, it's hard to pin point.
Any ideas?
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