A normal car usually has a normal and smooth sound. If you start to hear strange sounds around your car engine, let start to check your engine. That strange sound is sign that you has a broken car engine such as:

1. Regularly "klik-klik" sounds. It is happen because of valves moving. To fix it you must to reset you fissure valve at workshop.
2. Twang sounds when you increase your speed or adding your cargo. It is happen because of low octane gasoline, carbon precipitate, too fast starting time. To fix it you must change you low octane gasoline to a higher octane gasoline, clean the carbon precipitate and set the starting time to a normal.
3. A soft knocking sound when piston goes up. It is happen because of worn-out piston emplacement and common mistake when assemble piston. To fix it you must adding you oil to your engine.
4. Twice knocking sounds when machine is unloaded. It is happen because of worn-out or loose pin piston.
5. Vibrating sounds when you increase your speed. It is because of worn-out or broken ring piston or cylinder wall, and low tension ring piston.
6. A short chirp sounds at cylinder head. It's happen because of piston are scratching cylinder wall, broken piston, common mistake when assembling piston and it need more oil.
7. Knocking sounds between metal (when we increasing speed or adding weight on our machine). If it roaring periodically, it because of a worn-out camshafts emplacement. But it if is roaring unperiodicaly, it is because worn-out thrust bearing.

So, if you start to hear that some strange sounds on your car go to your workshop immediately before your engine goes down.