I lived in Canada for 20 Years and almost every car and truck had a block heater as George said remove a soft plug and they go in and tighten downwith a O ring I dont think I ever saw one leak that was installed right.One problem is to remove the soft plug with out driving it into the water jacket. Usually a small chisel could get a hole in it then just pry the sucker out.I am sure more tham one ended up inside the motor with on bad problems.I had a electric plug on a timer so I could plug it in when I parked and the timer would put current on a couple hours be for I was to leave. The heater would start heating up the car right away. I have an idea $25.00 would buy one now.