Leaking Engine Heater or Freeze Plug Leak?

don434don434 Member Posts: 43
I have a 1992 Chevrolet Suburban with 100,000
miles on my 350 engine.Directly in front of my oil
filter mount is either a freeze plug or engine
heater installation. For three months various
people haven`t been able to explain why I had
engine coolant leaking from the hole in the bottom
of my steel fly wheel cover.
Today there is a fast drip from the item mentioned
above. As I see it either a freeze plug has rusted
thru or the engine heater assembly is leaking.

Are special tools needed to remove freeze plugs or
to install a new freeze plug.

Are engine heaters installed in freeze plug holes
or is there a special threaded hole for these
units. Does removal involve soaking this area with
rust solvent and then using a normal wrench for

I have installed things like new starter motors,
water pumps, fuel pumps, radiators and plugs but
have never worked on block heaters or freeze plugs.
Should I leave this to a good mechanic?

Would appreciate your thoughts.



  • don434don434 Member Posts: 43
    Drained coolant and observed that the coolant heater apparently is threaded into the engine block. Problem is that the assembly has three lugs projecting upward about 120 degrees apart. Anyone know the G.M. part number for this special tool - or any other source for the tool?
  • alcanalcan Member Posts: 2,550
    GM block heaters are installed in smooth bore core holes, retained with a T toggle bolt and sealed to the bore with an o-ring. There should be a bolt head in the centre of the heater, 7/16" if my memory serves me correctly. To remove core plugs, drive the plug part way in by hitting it with a blunt punch on one side, cocking the plug in it's bore. Then pull it out with vise-grips or slip joint pliers. Remove ALL traces of corrosion from bore (scraper and sandpaper time), then coat the bore and new plug with liqid thread sealer and drive the new plug squarely in.
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