The Stovebolt Site Forums The Shop Area Engine Shop Freeze Plug

I'm cruising down the road in my 52 1/2t, 235 when bang. I pull over, take a look and find the front freeze plug blew out. The rad has a 4# cap so pressure should not be a problem. Question is. Is there any special trick to installing a freeze plug? Are they just hammered in? Do you us a sealant? These are not something that are replaced very often. Thx.

Glenn,

I remember two different types of soft plugs on that engine, a cup type and a slightly dished type. When I put them in I make sure the block opening is spotless and the I smear a coating of the Permatex brown poop, the type that hardens, around the edge of the plug. Use a driver to bang it flush. I wouldn't bang it from the middle, just from the edges of the cup.

On the dish type, I put them in with the same Permatex goop, and I do it with the dish OUT...after they come up on the little lip in the block, I give them one stout smack right in the middle of the dish. This seems to expand them and lock them in place.

It has always worked for me. If yours popped out with a four pound cap on the radiator, it was either the wrong size, in the wrong place or put in wrong...4 lbs isn't very much pressure.

Stuart

It had to be the wrong size or something. I've had them seep and the steel ones rust a hole in them, but I've never heard of one popping out.

Yes, they pop out occasionally. The dish type was most common in the front of the engine, installed as atomarc described. Striking the center of the dome tends to flatten the plug and expand it in the bore. It should stay put if properly installed.

Harvester

on the cup types i always tried to find a socket that would fit the inside diameter of the cup, makes a good driver to help keep it square..

Just a note: There are also rubber expandable plugs with a flat washer and center bolt to tighten the plug in the hole. They're great for emergencys and seal well.

Make sure you get them in right and tight. I had just finished a rebuild and the first time I took the truck out on the hiway and got it up to speed, the pressure blew out the oil galley plug on the back of the block. Puked a gallon of oil out in a matter of seconds, made a fine mess of everything, and I had to pull the engine back out of the truck to get a new one installed right. Needless to say, I was not a happy camper.

this seems to be a common problem with current freeze plugs today. i would guess the QC isn't what it used to be during the manufacturing process. using a small amount of permatex and the correct size driver makes all the difference. i have had to "stake" them with a chisel before. the PO had "honed" the freeze plug openings and really made a mess.