Don't ever go there again - that guy is obviously not interested in working on your car. There should be a number of shops in your area familiar with the W123, so keep looking. But the valve adjustment really isn't all that difficult, and for less than the price of one trip to a shop you can buy all the correct tools to make it even easier.

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Rick Miley
2014 Tesla Model S
2018 Tesla Model 3
2017 Nissan LEAF
Former MB: 99 E300, 86 190E 2.3, 87 300E, 80 240D, 82 204D Euro
Chain Elongation References