Learning by expensive mistakes - Hugo {P}
A garage owner openly admitted to mis diagnosing poor handling on a Cavalier Mk3.

Apparently the ride was very hard. He assumed it was down to the shock absorbers, so without further checking he changed them expecting the problem to be cured.

When he took it out for a test run, the ride had not improved. He duly sat down and went through a proper diagnosis and found the tyres to be over inflated.

The pressure was 60 psi!

Changed shock absorbers back and corrected pressure - car was fine.

Anyone else care to admit or know of similar?

Yes we can all have a laugh, but we may learn something as well.

Learning by expensive mistakes - DeeJay
I once worked for a garage which looked after a fleet of Minis and Metros for a large organisation. I recovered a Mini back to the workshop with reported engine noises . The foreman listened very briefly to it and declared the engine to be beyond help. I was given the job of fitting a brand new lump, which I duly did . On starting the new engine in the foreman's prescence it sounded exactly the same . A moments reflection and disconnecting the alternator drive belt cured it . The foreman was not at all bothered by his expensive mis-diagnoses and just rang the customer and told them we had noticed that the alternator was on its way out and would they like a new one fitted whilst we had the vehicle ? And he got away with it !
Learning by expensive mistakes - nick
A few years ago my wife was driving her oldish Toyota Corolla. At low speed, the oil light came on plus rattling. Luckily she turned off the engine and stopped quickly. I was busy so I let it be recovered to a local and well-respected garage. They correctly diagnosed oil pressure loss (took a lot of thought!) and said that they had 'checked it over' and a new engine was needed as the oil pump had failed and severe engine damage had taken place. As the car was rather elderly and not worth a garage-fitted new engine I had it moved home with the idea of putting a second-hand engine in myself. On closer inspection, I couldn't see what they had 'checked' as nothing looked touched so I had a look myself. The drive pulley for the belt-driven oil pump had come off the shaft, it must have been loose for a while as it was worn and would not sit tight on the key. As the engine had been stopped quickly I thought it was worth a punt on a new pulley. £20 later from Toyota and 30 mins to fit, one sweet-running engine that then did many 10's of thousands of miles and was fine when I finally sold it.
And colleagues wonder why I'm cynical about garages?

Value my car