An interesting question has been brought to my attention recently: Can a deaf person be a competent, safe mechanic?
I say yes. Hell yes, actually. The simple reason is that there is no reason a deaf mechanic can't kick ass.
Every 3 Months or 3,000 Miles
Whether a mechanic works for a Ford Dealership or Shade Tree Inc, there is a lot of general maintenance to be done. oil changes, cooling system flushes, A/C recharges, tune ups and even rotating your tires are part of regular maintenance throughout the life of your car. What's so special about these procedures? Not a damn thing.
I, along with the rest of e2's gearheads, could do those things with half our brains tied behind our backs. You don't need to hear anything to anticipate and perform any of the above maintenance. Even if you screwed up, there will be the visual clue of a leaking fluid or dye in the case of A/C system. You also don't need hearing for tire mounting, balancing or patching, alignment, brake jobs, or electrical system inspections. Even alternator / battery / starter problems can be chased down with simple current tests if you can't isolate the failing component by ear. A mechanic could perform enough of the maintenance encountered in a busy garage to stay well paid.
Light Maintenance
Nowadays, every car has idiot lights and an onboard computer system that monitors various sensors throughout the car. If problems are detected, a light notifies the driver and the problem is stored as a code in the car's computer. So all the driver has to do is say "So, like. . .this light totally came on and I was like 'We're out of gas!' but then I realized it was the car-thingy light so yak yak yak" and so on until the mechanic appreciates being deaf. Point is, for a large part of engine related problems, small diagnostic computers can tell a mechanic exactly what is wrong with the car. TPS, oxygen sensor, EGR valves all the way down to coolant reservoir levels have their own unique codes. The mechanic doesn't need to rely on his own hearing capability to isolate every problem in the engine.
What's more, no mechanic ever needed to rely on his own hearing capability to isolate every problem he faced. Do you ever go to a garage, throw your keys on the counter, and walk out the door? Hell no, you always tell the guy at the counter what symptoms or problems you've experienced. Of course you know there's something wrong, or you wouldn't be in there maxing out your Visa to pay for the replacement of your faulty canoodler valve.
Even if a customer has no earthly clue what makes their car stop, start and turn they do know when it makes funny sounds. They will tell you. Even if they just point you to a quadrant of the car, there is a small number of problems that are possible. Brakes? Shocks / Struts? Dead raccoon flopping around in the wheel well? Really, what the hell could be wrong (excluding the internal engine) that a good inspection won't catch? Not to mention the fact that a mechanic, regardless of their hearing, could probably detect the vibration of significant problems on a test drive.
"There's your problem."
The only problem I can imagine for a deaf mechanic is internal engine failures. Specifically, valve train failures could be a real pain. A mechanically challenged person may not realize that the noise they hear is a starving lifter. Of course, problems with the valve train could be determined but that would most likely involve a tear down that would run into a 4 figure labor fee in a hurry. Besides, events like this are so infrequent in a garage that I would imagine the job could be given to a different, non-deaf mechanic.
As opposed to the valve train, problems involving the crankshaft, rods or pistons are readily apparent, even to some trained monkeys. Similarly, transmission problems stand out without much input from your ears.
In short, I believe that a deaf mechanic can out perform a non-deaf mechanic. Some jobs will naturally proceed faster with the testimony of your ears, but that is not necessary. If a hearing impaired person did want to work as a mechanic, I see no reason why they could not be a competent, safe, productive member of any car garage. The majority of a garage's work will be routine maintenance or simple parts changes. With a minimal amount of experience, we could all perform these jobs without the need for our hearing. A simple shuffling of tasks could ensure that a deaf mechanic could stay busy with any number of assignments while jobs that are more quickly completed with auditory help are tackled by the non-hearing impaired mechanics. The business gets to keep on keepin' on and customers get screwed over on their canoodler valves.