Throwing Automotive Logic Out The Window

Hey folks, I am back in action today. Got some good stories about automotive logic, and throwing it right out the window. Sorry about missing Friday, but this week will make up for it!!!

There is no doubt that the diagnosis part of this job is one of the toughest. Racking your brain over problems that make no sense, all while trying to relate them to a component failure. It can be enough to make a mechanic lose their mind. Early on in my training, I was taught to always follow a logical repair process. That is a 100% true statement. I would not start diagnosing a tire going flat, by checking the oil. This process is reinforced in our yearly training as well. Of course in a training class, nothing ever goes wrong does it. ;)

There are some basic strategies to diagnosing cars, or anything really. Doing things like “working easy to hard”, “Keeping it simple(stupid), and making sure you are diagnosing the problem not just the concern. if a mechanic follows these simple steps, they will be able to diagnose most issues. This is a lesson that i try to ingrain in all of the young mechanics that come through the shop.

There are times for every mechanic that they get their butts kicked by a car. One of the great things about being at a dealer is we have several layers of assistance to help when a mechanic cant fix a car. Then there are the times that all the assistance in the world doesn’t help, and you have to throw all the logic out the window. The following stories are real. The names have been changed to protect the innocent. There are really no names in the story btw ;)

Beetle Transmission Problems

A customer bring their car in because it was making a horrible noise at about 45mph. The mechanic test drove the car, and did some checking. The thing about transmissions is, failure is rarely absolute. Meaning that being 100% sure of the diagnosis is rare. Usually it takes repairing the concern before you know if it repaired it.

Well, after several test drives, and checks, he decided to replace the transmission. Now, replacing a transmission is not a hard job, but it takes time, is a lot of work, and does not pay really well. It is not something mechanics do for fun! After getting the work done, the mechanic test drives the beetle again. Guess what, noise is still there. Well more checks, and diagnosis follow. The problem turned out to be an 30 second fix. The customer had a Disney ball on their antenna. For some reason, at 45 mph, the ball would catch the wind just right, this would cause a vibration in the antenna, that traveled down into the roof.

TDI Transmission issues

Very similar to the story above. A customer brings their Passat TDI in for a shifting issue. The mechanic drives the car, and verifies the problem. Now this particular TDI engine had just come out, so the information was pretty limited. The mechanic followed the steps he should, and again, decided to replace the transmission.

With a fresh transmission, the mechanic test drove the car. Would you believe that the car drove great, at first! The mechanic let the car sit for a while and test drove it again. Sadly, it was doing the same thing as before replacing the trans. It turns out that the car had a very slightly clogged fuel filter. That small amount of difference in fuel quantity cause the engine to “stall out” when shifting. The only thing felt by the customer and the mechanic was the poor shift. After a new fuel filter, the car was 100% right.

TDI Engine Locked Up

This time, the customer had his TDI towed in, because it would not start. At first it sounded like the battery was dead. The mechanic tried to jump start it, but that was a no go. We towed the car into the shop for further diagnosis. A full starting system test did not reveal anything. The mechanic noted that it smelled like the clutch had burned up. So he removed the starter to check for damage. Didn’t find any.

He attempted to crank the engine over by hand, and was not able to. Even an almost 3ft wrench would not move it. The mechanic removed the valve cover, and oil pan to inspect for internal engine damage. Well, he didn’t find any. We all got to talking, trying to brainstorm and get ideas of what to do next. Just about the time he was going to recommend removing the cylinder head, I suggested that he take the serpentine belt off. That is the belt that runs the alternator, a/c compressor, and power steering pump. When he removed the belt, the engine would turn over normally.

It turns out that the pulley on the alternator locked up. As powerful as a starter is, it was not able to overcome the small pulley. I could not believe that the belt would not just slip over the pulley and let the engine start. I had seen this happen 1 other time, I just wish I would have remembered it before he took the other parts off. As soon as he finishes it, I will update on what happened.

I know there are many more stories just like this out there. If you have one, contact me with the story, and I will share it with everyone. All the repair logic in the world would not have helped in some of these situations. Mechanics need a repair process, but they also need to know when to ditch it and try something random!

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15 Responses to Throwing Automotive Logic Out The Window

  1. Garrett Craven says:

    I like this post. Ive got a good one too. Its actually how i came across you charles!

  2. Joe D says:

    Don’t forget about the axle vibrations at idle on a diesel passat!!!! Those are a doozy!!! :-)

  3. Brandon says:

    My question is, if you do something like a transmission replacement, and find that it wasn’t the problem, that the transmission was fine on the first place, do you charge the customer for the new transmission? because that sounds expensive and i would be mad if it wasn’t even an issue!

    • Charles says:

      Brandon, the customer was not charged in either one of the 2 transmission stories.

      In the story about the alternator, we gave the customer a really great deal on the labor to replace the alternator.

  4. Why its important to have an honest mechanic. A dishonest would have left you thinking the transmission was the issue.

    We switched shops one time after a bad experience. New shop fixed issue, but another issue cropped up while they were working on the first. They fixed the 2nd at no extra cost, and apologized for taking longer and they had to wait on the part. I became a true fan.

    • Charles says:

      You hit it right on the head Heidi!

      I am glad your second shop got you all fixed up! I love hearing stories about shops doing the right thing, and doing it with our the customer raising hell.

  5. Garrett Craven says:

    Hahahaha! Thats great

  6. Pingback: Throwing Automotive Logic Out The Window, Readers Story | Humble Mechanic

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