TR2/3/3A The Aluminum Plug in the Cylinder Head ?[Again]TR3

[karls59tr]

Not sure if this is a dumbass question or not but what was the reason for an "aluminumn" plug in the head? Was this in case the water? froze in the engine block, the plug would be forced up and relieve the pressure, similar to the frost plug in the block? The original plug in the TR3 head was replaced at a rebuild with another aluminumn plug only this one was threaded into the head.(been in there for years with no sign of corrosion.) If they do corrode ,as was mentioned before, would I not be further ahead with a "cast iron" NPT plug to avoid corrosion issues? On the other hand aren't there aluminum compatible antifreezes on the market that would make corrosion a non issue? Randall?

 

[CJD]

"Freeze" plug is a misnomer. If the coolant does freeze, you will not save your block or head. They will crack. Sorry, don't know why they would choose aluminum for a plug material.

John

 

[TR3driver]

Like most "freeze plug" holes, the hole in the head was actually used to help support the cores that form the coolant passages during the casting process. The cores are normally made from sand that is only lightly stuck together (so it can be broken up and removed once the cast iron is cool), so they need to be well supported in order to not break or shift during the casting process. Once the casting is finished, the hole is of no further use, so it gets "permanently" plugged.
https://en.wikipedia.org/wiki/Core_(manufacturing)

BTW, there is no "freeze plug" in the block on TRactor motors, because they are cast without the liners in place and thus there are plenty of places to support the cores. Go look

There are some other plugs of course, but they also have to do with casting or machining processes. There is no attempt to preserve the block during freezing.

You are quite right, the plug should not corrode, IF the antifreeze is always kept up to date. Antifreeze contains various compounds to protect the aluminum.

But, those anti-corrosion additives wear out over time, even if the engine is not driven at all. Most people don't bother changing the coolant when they haven't driven the car, which allows the corrosion to proceed. If you look inside the thermostat housing, you can get some idea of how bad the problem is. On my previous 56, it was literally paper thin in places and had been 'buttered' with some sort of adhesive to try to stop the leaks.