Yanmar 4JH2E freeze plug leaks

[lwilhelmsen]

I have a 1993 40.5 with a Yanmar 4JH2E engine with about 3400 hours that I have owned for about five years and bought in Canada and now keep in Seattle. About two years ago I developed a pinhole leak in the freeze plug just below the exhaust elbow. A mechanic said it would cost about $500 to repair so I drained down the antifreeze, cleaned up the hole and pushed epoxy putty in the plug. This has help up but I now have a few tablespoons a month of leakage from this plug and another on the other side,
Has anyone had the problem and what did you do to fix? How often do you change antifreeze? Would radiator stop leak work? I have an Espar heater that circulates the antifreeze through the system also. Plan to replace all antifreeeze soon and would like to do it with a stop leak if safe to do.

 

[Rick D]

Good Luck With That...

...from over 50 years with a bunch of British and Italian cars plus a few beaters, it is my experience that stop leak products are very temporary solutions at best. The coolant should be changed every couple of years (I believe annually is recommended). Time to bite the bullet. I have changed but one freeze plug many years ago, but I recall it wasn't a big deal once I had removed enough stuff for comfortable access. FWIW,

 

[Alan]

Changing a freeze plug is a simple matter of removing the old and popping in the new. The hard part can be access to them, what do you need to remove to get at it?
To save yourself from ever having to deal with this problem the answer is to flush the fresh water side out regularly. Anti freeze starts out pH neutral but over time changes to a mild acid which attacks everything it touches. The thinner the metal the sooner it will develop a leak. Hot water heaters are notorious for this.
Freeze plugs come in many different styles. Almost any one will work to replace another of the same size.
Long or extended life anti freeze has a usable life of five years. What this means is it takes longer to break down and become acidic. It is a good choice for both your car and your boat.