358156 and P&P are right on.
Tom, I didn't take offense, and I get what you were trying to say, it's just that the whole deal is more complex than it first appears.
What the tech did with the oil was quench just the bolt stub to shrink it loose. Water cools parts faster but boil point can be too low for spot-quenching a tiny screw stuck in a huge heat sink and it just steams off. Having knowledge of and
thinking about how to make physics and chemistry work FOR you when working on machines is practically a requirement of the job.
I'm an ASE Master/L1 certified auto technician (plus others, now expired), a mechanic, an educated but un-certified engineer, a trained but uneducated computer network technician, a mind reader, a healer, and some days feel like a bona fide miracle worker. The problem with trying to define the qualities of any tradesman is you must be able to stand in their shoes for a bit and see what they ACTUALLY do, not just what you IMAGINE they do. For example, I could say there are pilots and there are plane drivers:
"Plane drivers wear shoulder boards to work, poke in a destination on a guidance computer, hit the go button, maybe turn the big heading knob on the autopilot console when ATC tells them to, and screw off the rest of the time in the air. When a mechanical emergency arises, they have a hard time because of lack of basic stick-and-rudder skills. I could then say that pilots on the other hand fly manually a lot and really understand their machine, its full performance envelope, and how to handle it in adversity. Pilots don't need nobsteenking checklist, they memorized them all for every scenario on every type rating."
Truth is I don't know any more about Sully's or Snort's line of business than the man in the moon, yet it's easy to THINK so and make uneducated and mostly false assessments regarding automation and the loss of "real" flying skills among commercial aviators or to think a Tomcat pilot could land a loaded passenger jet deadstick in a river and everyone walk away.
A mechanic/technician is more or less forced to be an over qualified parts changer because sub-assemblies are deliberately designed to not be serviced in the field. The reason we don't just put brushes, bearings, and a rectifier bridge in a worn out alternator is because the Delco 10SI hasn't been put in vehicles in over 30 years and we can't get parts for modern ones very easily. Another reason is warranty and cost. If I rebuild something and it quits again in a week, I get to do it again for free. If I change a part and if quits in a week, the manufacturer or rebuilder pays me to replace it again. Still another reason is liability. I used to overhaul brake calipers, wheel cylinders, master cylinders, steering gears, power steering pumps etc. because $5 in seals and the labor to rebuild was more money in my pocket and overall often cost the customer less than slapping on a reman part. I had fewer problems than with rebuilt garbage. However, lawyeritis has ruined all that. The expense of machine tools precludes resurfacing heads and doing valve jobs. Tolerences are so tight a warped head often can't be surfaced anyway.
The derogatory term "parts changer" means someone is incapable or unwilling to properly pinpoint the failure point and throws parts at the problem hoping it will go away. Plenty of that going on. There's a flipside though, like the diesel Jeep that came in for a check engine light due to a stored, intermittent dtc for an egr pressure sensor circuit. I read through the diag procedure and priced the part. Due to difficulty in accessing any of the wiring, harness connections, or involved computer modules, I advised the customer that I could throw a new sensor at it for about $100 parts and labor and have a really good chance of fixing it, they could have the vehicle back right away and drive it for a few days to confirm that fixed it, or I could keep their vehicle several days to tear into it to positively pinpoint the problem in between other jobs the tune of $500-800. We threw a sensor on it and two months later it's still fixed when they came back for a routine oil change. All we can really do as techs working on computerized equipment is check the inputs, outputs, wiring, and communication signals and change the bad component or repair bad connections. It would be nice to have access to the software programs and more complete descriptions of the computer strategy, but at the end of the day we techs don't always need to know why a failure occurred, only what part is causing the failure and have reasonable assurance that we have found the root of the problem so it won't keep happening.
A customer's AC wouldn't work. Another shop had put a compressor and then an engine computer on it because the clutch would only blip and wouldn't stay on. I fixed it with another computer and a relay. The relay was the root cause because of low resistance in the coil. Low resistance was letting too much current to the ecm's internal ground-side control transistor, causing it to fry. The relay coil was only about 10 ohms below specification, but it was enough to fry the transistor. The first shop failed to properly test the whole compressor clutch control system to determine WHY the computer had fried. Parts changers? Maybe they just lacked all the information they needed about the system and guessed? Maybe too busy/too much pressure to spend the time to do it right? I don't know because I wasn't there, so I won't throw stones.
I think the discussion boils down to the increasing technical complexity of machines outpacing older generations, needing computers and a lot of technical education AND common sense instead of just common sense to fix stuff, and the timeless problem of varying degrees of competence. Your best auto mechanic from 1980 couldn't even replace a battery on a 2020 Ram pickup without causing a myriad of problems. Your most qualified young tech at dealership likely couldn't tune a carburetor or use a dwell angle meter if their life depended on it, but likely figure out why your phone won't link with the integrated center stack or why your selective reduction catalyst isn't regenerating like it should.
