Once in the keyhole, does it turn freely?

As for the hair dryer, just put the key in the keyhole, hold the dryer 1/2 inch away from the key, and blast it for 5 minutes on high. The heat will slowly be conducted into the lock mechanism. Hair dryer is a good choice because it is not too hot, so there is no damage potential.

Best of luck.

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1986 300E 5-Speed 240k mi.