94 toyota truck has a clicking sound under hood

See if the alternator is putting out less than it should that is what mine sounded like....will have a dead battery unless you use it everyday and it doesn't sit much.

ROBERT F. THOMAS

start by disconnecting accessories. If you can pull off the belt that connects the power steering pump and the clicking stops (like mine) you'll know what it is, same for the alternator, otherwise if you really want to do it yourself everyone recommends using a mechanic's stethoscope and trying to figure out where exactly the tap is coming from. Could be anything from valve tapping to a missing bolt in your exhaust manifold...

I usually use the shadetree mechanics stethoscope. Take a long socket extension, place your thumb over the wrench end, place your thumb in your ear and touch the opposite end to the suspected components. It's amazing how well this works.

Hope this helps.

NES