Connecting rod bearings are crucial components that allow the crankshaft to rotate smoothly. When they wear out, they develop play, and the crankshaft doesn't spin as smoothly. This results in a distinctive clattering or rolling sound, much like the description you gave. The sound is usually more noticeable at higher engine speeds and can change in intensity.
It's extremely serious. Worn connecting rod bearings can lead to catastrophic engine failure if ignored. The crankshaft can eventually seize, resulting in extensive and expensive damage. Ignoring this sound could mean a need for a complete engine rebuild or replacement.
Other possibilities (though less likely given the description):
* Loose or worn rocker arms: These could also create a clicking sound, but it might be less of a rolling sound.
* Wrist pin noise: A worn wrist pin connecting the piston to the connecting rod can also make noise, but the sound is usually different.
What to do immediately:
* Do NOT drive the car. Continuing to drive could cause irreversible damage.
* Have a qualified mechanic inspect the engine as soon as possible. A diagnosis is crucial to determine the extent of the damage. The sooner this is addressed, the less costly the repair will be.
The golf ball rolling sound is a strong indication of a serious internal engine problem; don't delay getting professional help.
