Re: 58 Mercury Monterry oil or transmission leak

[Roy & Brenda Lange]

Not shure how close to top of your trans dipstick tube is to the back of the intake manifold, but on my 53′ Merc, when it was overfilled, (also possible if converter leaks out into the pan) it blows back up the dipstick tube and out the top. It just might be possible that when it hits the dipstick cap, it is directed towards the back of the manifold….just a thought. You might  let it sit overnight, then lift the hood and start it up and see what happens….mine sat from 1982 until 2009.