Common Mistakes That Auto Owners Make

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oil leak

With over a quarter of a century spent in independent garages, I cannot count the number of times that I have seen a do-it-yourself mechanic cost himself extra money with an improper repair.

Many times, mechanical failures that would have been classified as minor, initially, were mishandled to the point that they required a major repair; often too major for the amateur mechanic to undertake.

At this point the vehicle is delivered to the auto repair shop, where steps are taken to rectify the situation, typically costing hundreds of dollars more than the repair would have cost if the vehicle were taken there, initially. Here are a few of the mistakes that I have witnessed, personally.


Bob’s High-Dollar Oil Change

An extreme case of the “do-it-yourselfer blues” proved very costly to treat, when an aircraft engineer, named Bob, decided to change the engine oil in his 2002 Chevrolet Tahoe 4X4. This task was one that he had accomplished numerous times, without a problem but this time would prove to be woefully different.

He drained the crankcase, without incident, and attempted to remove the oil filter before incurring any difficulty. When he could not remove the filter with the designated tool, he elected to drive a screwdriver through the body of the filter in an unsuccessful attempt to remove it from the engine. Not a huge problem — not yet, at least.

Even as a professional automotive technician, I find that the overall quality of the repair that I perform is directly affected by the decisions that I make. Bob made a poor decision, when he poured new oil into his Tahoe, and departed for the local garage with the screwdriver stuck firmly in the oil filter, and the oil filter still screwed on the engine. He thought that he could make it. The shop, where he had been a loyal customer for many years, was only about a mile from Bob’s house.

I remember well the moment that I saw him walking into the parking lot. He informed me of the situation, said that he had already called a tow truck, and we waited for the Tahoe to arrive.

Bob hoped, even prayed, for the best but the diagnosis was grim. The 5.7-liter Vortec V-8 had ran completely out of oil and thrown a rod. I felt so bad for Bob that I gave him a ride to his house, myself. I can recall him giving me directions to his home and me not having the heart to tell him, “I can just follow the trail of engine oil.”

The moment of truth came when Bob’s dear wife, a rather demanding and critical woman, inquired as to the condition of the vehicle and how much it would cost to repair it. To intensify the situation, she had recommended to Bob that he have the oil changed at the shop. She then proceeded to blow a gasket. The oil change eventually cost this careless owner nearly $5,000.


I wish that I could say I had not seen similar situations occur with some degree of regularity.

  • I have seen plastic fuel lines broken by a graphic designer, who attempted to change a fuel filter, without the correct tool. A fifty-dollar repair, performed at a reputable garage, cost him over $500 to replace the fuel lines.
  • I have replaced an Anti-Lock Brake Control Module, because a trim carpenter failed to open the bleeder valve when compressing a caliper piston, while performing a brake job. This forced fluid into the hydraulic control module and damaged the actuator seals. A repair which would typically cost around $125, ended up costing just over $1,500.
  • On one occasion, I replaced a rear differential because a heavy-equipment operator, after a routine service,  forgot to remove his grease rags from the housing before re-installing the cover. This cracked the housing and ruined its contents. A $100 service mutated into a $1,000 repair.

I could continue with incident upon incident, but I hope that you get the idea. There is nothing wrong with doing it yourself; as long as you make wise decisions, and know your limitations.

S.M. Darby

S.M. Darby

I am a freelance author with over 25 years of experience as a professional, ASE certified automotive technician and shop owner, muscle car enthusiast, avid street racer, and classic car restoration specialist.