thrumming noise?

[90volts]

i was just about home, turned a corner at a light and noticed a thrumming noise from behind. it seems to be with the engine. if i disengage the clutch or have it in neutral , when i hit the throttle the noise goes along with it. i haven't done anything yet. just got down to see where it may be coming from. sound like an echo of the exhuast- sort of like a vacuum cleaner.it still drives fine, not that i have been doing much more than 15 since i heard it, but it gets louder the higher the rpm it seems. any ideas?

[167luckycharm]

Hi, Several things come to mind; Throw-out bearing starting to go bad...noticeable when pressing and releasing the clutch while in neutral with the engine running. Alternator or generator bearing starting to go bad...eventually happens when the bearings are exposed to rain and or sand, or fan belt was adjusted too tight for a long time. Debris stuck somewhere between fan and housing. I found an empty ziploc bag stuck in my fan on my bug engine...picked it up while driving down the highway somehow. Shut the engine off, disconnect the fan belt, and spin the pulley by hand. Listen for grinding or rubbing noise, the shaft should spin freely and quiet. Check if your fan belt is starting to de-laminate or if it is too loose. Sometimes the inner strip separates and flaps against the groove of the pulleys, or the sound could be from the slipping belt. Always good to have a spare belt tucked away in the car. Good luck!