Can I sue if a mechanic knowingly left something under my hood that caused me to briefly lose steering. No injury because I realized before leaving

As the old saying goes, no harm, no foul. Damages are an essential element of any lawsuit. Without any damages, there's no point in bringing a lawsuit. You can always report the incident to the mechanic's supervisor to put him on notice of the individual's arguable incompetence. Best regards, Jonathan R. Ratchik, Esq. Kramer, Dunleavy & Ratchik, PLLC www.kdrpilawyers.com