So far, every suggestion in this thread has been either a WAG or a SWAG. The veterans on the forum will understand those terms immediately- - - -others might need a translator. The fairly recent invention of small, durable, and inexpensive cameras has opened up all sorts of ways to see what's going on in formerly inaccessible places like under the hood during a test drive. Hence, my suggestion of a GoPro, even if an underhood light might also need to be used. It beats all the guesswork!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!