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By lovefordgalaxie - 14 Years Ago
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Some time ago I was having trouble with freeze plugs. Replaced the one that was leaking, and the repair lasted one year. the new one started to leak as well. My coolant has the decent amount of antifreeze, so it's a odd thing that just one plug keeps giving trouble. I have a custom plug made, machined out of aluminum (solid, flush with the block). It sealed ok, and I doubt it would give me corrosion trouble again. My fear is about the aluminum expansion being different from the cast iron of the block. What do you thing guys, is there a chance of the plug ruins the block? It was press fit, with epoxy sealer.
Any imput would be very appreciated.
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By GREENBIRD56 - 14 Years Ago
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Stamped brass freeze plugs are often used and their coefficient of thermal expansion is way different than cast iron. Their ability to stay sealed may have more to do with their shape than the material used. The cupped shape of the stampings may conform better to the differences in size as they go through the thermal range of the engine block. Try to check the Ph of your coolant mixture if you can - it needs to stay neutral, tending toward "base". There are "test strips" (litmus paper) used in the trucking industry to check this and they may be available to you. Gardening enthusiasts also have acid/base testing gadgets too. If you check and find the coolant has shifted toward too acid a mix - add four or five drops of ammonia to the radiator - one drop will shift one gallon by about 1/2 point on the acid/base scale.
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By lovefordgalaxie - 14 Years Ago
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Yep, I did a test with "tornassol" paper, and it was ok, as well as a density test for the solution, and the proportion of antifreeze was ok also. It's always the same plug that goes bad. This time i gave a try with a solid aluminum plug. Hope it doesn't pops out, or damages the block. I can always pull it out, but untill now its sealing. I'm only worried about possible (a) block damage, and (b) the thing popping out.
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By 46yblock - 14 Years Ago
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Nice info on the pH testing. I have on hand strips of litmus paper for testing grape pH and will give them a try. It seems to me that the aluminum freeze plug wouldnt damage block, but might over time have electrolytic corrosion due to being in direct contact with the block.
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By GREENBIRD56 - 14 Years Ago
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GM recommends shifting the water Ph from neutral by 1 to 1-1/2 points toward "base" to protect aluminum heads, blocks or radiators. Labs use ammonia to shift distilled water (which usually comes 1/2 point toward acid due to atmospheric exposure to CO2) - toward base. The usual recommendation is to add one drop per gallon of distilled water to make the 1/2 point shift toward neutral. In the instance of the specially made plug - I doubt that the temp range and diameter of the plug is sufficient to cause an interference problem. Though the difference of thermal expansion is there - its not too big when considering the relatively small size of the plug and both parts will receive exposure to the exact same temperature.
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By lovefordgalaxie - 14 Years Ago
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Untill now, it seems fine. I just did some calculations (at last) with the plug's diameter, and with the expansion coeficients from both, cast iron and aluminum. A lot of interference force is generated, but not enough to damage the block (Thank God). When considering the expansion of the cast iron, the hole for the plug will expand like if it was solid. The interference force is generated, because the aluminum will expand almost twice, but we are talking of infinitesimal numbers. Probably, higher interference force is generated by introducing a "normal" plug into the block. Aluminum is a more ductile material than cast iron, or steel. Electrolisis may have something to do with the fact that only one of my plugs corrode. the negative battery cable is very close. Maybe the plug is acting as a "sacrifice" material, rusting instead of the block.
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By PF Arcand - 14 Years Ago
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Tulio: You may be on the right track about the sacrificial effect. You might try looking up "marine anodes." I seem to recall that some anodes are a zinc/aluminum alloy.
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By lovefordgalaxie - 14 Years Ago
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Yes Paul, the tought came to mind just because of that. The Brazilian Navy uses this kind of protection on ships hulls, and I think that the United States Navy also does that. In Civil Engineering we use this same effect to protect steel structures, like a bridge, for example. I think it may really be the case, but all Galaxies from around here, with a 272, or a 292 have the battery cable at the same spot. Why is just mine "eating" the plugs? I think there is another detail involved causing this to happen. Maybe some kind of current drain trough the starter, a very small one, but enough to cause this to happen. maybe I left the book Christine too much time inside the Galaxie.
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