Mitsubishi Pick-ups and Montero 1983-1995 Repair Guide

Core (Freeze) Plugs


See Figures 1 and 2


Core plugs need replacement only if they are found to be leaking, are excessively rusty, have popped due to freezing or, if the engine is being overhauled.

If the plugs are accessible with the engine in the truck, they can be removed as-is. If not, the engine will have to be removed.

  1. If necessary, remove the engine and mount it on a work stand. If the engine is being left in the truck, drain the engine coolant and engine oil

When draining the coolant, keep in mind that cats and dogs are attracted by ethylene glycol antifreeze, and are quite likely to drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantity. Always drain the coolant into a sealable container. Coolant should be reused unless it is contaminated or several years old.

  1. Remove anything blocking access to the plug or plugs to be replaced.
  3. Drill or center-punch a hole in the plug. For large plugs, drill a 1 / 2 in. hole; for small plugs, drill a 1 / 4 in. hole.
  5. For large plugs, using a slide-hammer, thread a machine screw adapter or insert 2-jawed puller adapter into the hole in the plug. Pull the plug from the block; for small plugs, pry the plug out with a pin punch.
  7. Thoroughly clean the opening in the block, using steel wool or emery paper to polish the hole rim.
  9. Coat the outer diameter of the new plug with sealer and place it in the hole.

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