Questions on brass casting plugs

[siteunseen]

Should I use Loctite or brush on gasket sealer? Will freezing them make them easier to go in? Parts guy suggested getting them cold. Thanks for any replys.

[Bonzi Lon]

On page 113 of 'How to Rebuild Your Nissan & Datsun OHC Engine', by Tom Monroe, "Although it's not essential to use sealer on the core plugs, I do it just to be sure." "Use a mallet and large-diameter punch about 1/16 inch smaller than the ID of the plug".

Bonzi Lon

[siteunseen]

That's the instruction book I'm using, ha! Thanks Bonzi Lon. He says use silicone (pic #3) but alot of newer stuff I'm reading says no silicone anywhere because of it "rolling up" and breaking off then clogging something up. They swear by that Permatex brush on gasket sealer but Loctite has also been mentioned. Seems like Loctite would be the best but I thought I'd ask. Also read that brass could blow out due to pressure before the thermostat opens. Anybody had that problem? Seems plausible because brass is intended for marine motors that don't build as much pressure.

[Bonzi Lon]

Personally, I would not use a silicone product or freeze. Silicone by nature is slick as snot, I'd use a rubber based sealer, very thin smear. Freezing will shrink them & make them go in easier, but will you get a good seal? By NOT freezing them the softer brass will be allowed to deform to the irregularities of the harder cast iron, thus a tighter fit & insurance from the gasket sealer. The thermostats are about 13-15 lbs, doubt that would be enough to pop one out, if it takes more than that effort to put them in.

Please chime in if I'm off base.

Bonzi Lon

[siteunseen]

Dead on. I ended up using red Loctite though, thin film too. And my Dad said that was why people call them "freeze plugs" because colder makes them shrink but by the time you get them coated and ready for hammer time they'd be back to normal size so it makes no sense to to him. I like your reasoning too, makes perfect sense. Thank you for responding.

[grantf]

I thought they were called freeze plugs because they are designed to pop out if the coolant froze, preventing damage to your engine.

Where I grew up Alaska cars would have a heater plug to replace one of them so you could plug you car in at night and keep the engine warm in order to make it easer to start in the morning.

Edited March 5, 2012 by grantf

[Bonzi Lon]

Both terms can be used. The only reason they are there is part of the casting process. In order to make the interior cavities for water, a sand casting 'core' (special sand pre-formed to the interior passages), is placed into the mold for iron to surround. The core is supported by the mold itself causing the hole in the side of the casting. I assume, very early in time, without antifreeze, the plugs were popping out due to freezing, thus the name. So, there are two names for one part, although 'casting plug' is the proper term, we all call them freeze plugs.

I spent 4 years in a small ductile iron foundry, hottest, hardest, dirtiest, most fun job I've ever had.

Bonzi Lon

[Diseazd]

Also read that brass could blow out due to pressure before the thermostat opens. Anybody had that problem?

I blew a freeze plug out once by running too many RPM's before the thermostat opened.........6500 RPM when the temp needle was at 1/4. Pumping all that water into a dead end block must have been too much. Experience is a good teacher!