I had my truck overheat yesterday fairly suddenly. When I got parked I found a freeze plug that had been replaced by a shop (because the old one was rusty) had popped out. It had been odd to me that the radiator hadn't boiled over or my electric fan come on.

Today I set out to see about fixing in. The plug was on the passenger side just between the starter and the motor mount. I've never installed a freeze plug but read up on it. I got a new plug and found a socket that was exactly the same diameter. What I couldn't do was find a way to swing a hammer in a direct way to line up the freeze plug. I did manage to seeming get it in straight and very slightly into the block (tiny space between edge of freeze plug and the side of the block. I used a thin coat of Black RTV as a seal.

When I went to test it, I found the engine beginning to overheat again (210 when I shut it down). The radiator was cold to the touch and my electric fan which is activated by a thermostat at the bottom of the radiator didn't come on.

My theory now is that the Thermostat was sticking closed and not allowing hot water back into the radiator to cool and the pressure blew out the first freeze plug.

While I was warming the engine up, I was looking at the freeze plug and saw a couple tiny drops of coolant squeeze out the edge of the plug. I feel like the seal hasn't been made and/or I haven't driven it in far enough. I also feel like it's unlikely I can drive it in any better with the engine in the truck.

A mechanic neighbor is recommending that I get and install an expandable freeze plug, that he's had good luck with them. It's also been suggested to me that I shouldn't have used used Black RTV. I am now in the process of replacing the Thermostat. I've forgotten what temp T-stat I'd used.

Thoughts or Advise on Thermastat to use, using expandable plug, sealant to use on standard freeze plug?

 

Hi OBT,


Can you squeeze a small scissors jack in there and use that to press the new freeze plug in place? Just a thought...


Jay

 

if the hole was pitted get a new freeze plug (brass) put it in the freezer for 24 hours
remove old freeze plug and clean the hole up lightly , smears the new F/P contact areas with a thin layer of JB weld . install and let sit for an hour or two before adding Coolant .
your seeping should be gone

 

If the thermostat doesn't fix your overheating, I'd wonder what happened to the old core plug that the shop "removed" - it could be inside.

Ever use an air chisel? That and the right socket, and you could drive in the freeze plug, if you have enough room.

 

The freeze plug, brass, needs to be flush with the block or it's not seated and I have used a thin coat of RTV Ultra Black with great sucess on freeze plugs.

 

If in a tight spot, you need this tool to install a core plug with the engine installed: