A tap is a tool that cuts threads, but if something had existing threads it can help clean up the threads if they are a little messed up because of someone crossthreading a hole.

If you have already driven it, its probably fine. If the threads were pretty good, and just needed some cleaning I highly doubt there was much Aluminum debris in your cylinder. However putting in a helicoil requires drilling out the threads, then taping, then putting in the helicoil insert, which I am certain puts a lot of debris in your engine. Some mechanics will try to blow the chips out or vacuum them out with an air vacuum.

I hope everything is ok. Maybe change your oil soon and check. It probably got pushed through the exhaust system already if there were any chips.

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Current Stable:
1994 S500 v140, 210k miles, white with grey.

Former Mercedes in the Stable:
1983 300CD Turbo diesel 515k mi sold (rumor has it, that it has 750k miles on it now)
1984 300CD Turbo Diesel 150 k mi sold
1982 300D Turbo Diesel 225 sold
1987 300D Turbo Diesel 255k mi sold
1988 300 CE AMG Hammer 15k mi sold
1986 "300E" Amg Hammer 88k mi sold (it was really a 200, not even an E (124.020)
1992 500E 156k mi sold
etc.