It looks like a good day ahead. You just had a good breakfast and are about to go to work. As you ride on your car, you hear tapping or ticking sounds under the hood. It might be due to the weather you think, but it seems to be sunny all day. You ignore it and proceed to go to work, but while during driving, you hear the tapping and ticking again. Is it still safe to drive? Should you call a mechanic now? Should you pull over and check under the hood? These are the questions that you shouldn't have been asking in the first place if you only knew how to diagnose engine tapping or ticking sounds.
Understanding the different sounds from under the hood can help a lot in deciding when it is safe to drive. It will also help you describe the problem to the mechanic should in the event the problem is worst.
Examine where the sound is coming from. The noise may be coming outside or inside the hood. If it is outside you just have to check the exterior of the car for possible loose connections. If it is inside then serious cases may arise. To be sure that it is indeed coming from inside the hood, more specifically from the engine, press on the gas pedal. Press the pedal lightly at first and gradually press it until it reaches the floor. Noises that vary with engine speed will most likely be coming from the engine. In this case, the suspect is the fuel pump.
The ticking noise occurs during start-up. Sometimes, you will hear ticking noise during start-up. Observe if the ticking goes away after a few seconds. If it does, you may just need to check if the level of the oil is within the allowable level. This might be caused by low oil. Just top up the oil and it should do the trick. However, if the noise won't go away after you start-up, and you already checked the oil level and it is ok, then you maybe encountering a pretty bad problem. The noise could mean that the oil passages are blocked or the filters or oil pumps are failing. I suggest you consult an expert mechanic and describe to him the noise you have been hearing.
The tapping noise came from the engine's lower part. If you suspect that the noise is coming from the engine's lower part, you might be encountering problems like malfunction of connecting rod bearings and crankshaft bearings or the connecting rods are broken. This problem entails removing the engine to disassemble and rebuild the the engine's bottom end. Depending on the severity of the problem, it may cost you the whole engine in the worst case scenario.
Some noises that come from the engine indicate minor problems only, and can be handled by most of the drivers. If you hear an unusual engine noise, visit the repair shop for a diagnosis. Some service stations are offering engine check up for free, so you might want to take advantage on that.