The issue of blown head gaskets in most cars is generally caused by these reasons:
(1) Walking. The heads walk on the gasket as they expand and contract with heating and cooling. The greater the heat expansion co-efficient between the block and head, the sooner this happens and the more the walking occurs. This is an engineering and metalurgy issue that the owner has no control over.
(2) Electrolysis. When there are any conductive minerals in the antifreeze and water mixture , electrolysis occurs. Tthe aluminum is an electically hotter metal than iron. The electrons leave the aluminum and travel through the antifreeze to the iron. This leaves small pinholes in the areas exposed to the antifreeze mixture which eventually allow a channel for exhaust gasses to leak from the cylinders to the water jacket. This issue can be minimized by using the right antifreeze, and changinging it yearly. Use of distilled or purified water helps slow the process by removing minerals that can conduct electrons. Using tap water that is high in minerals accelerates the process. Hence, someone who uses tap water that is high in minerals to refill their radiator might see a BHG caused by electrolysis even though they do a good job of never allowing the car to overheat.
(3) Overheating. I believe this is the most common cause. ALL Acura Legends fall prey to the cracked radiator failure. When this is not caught early on, the fluid level lowers and air collects in the high points in the heads. The lack of fluid causes the heads to overheat. This in turn causes the temper of the aluminum to change and the heads begin to warp. This causes a BHG. Other reasons for overheating are many but the 2nd most common cause is not understanding the chemistry behind antifreeze. Simply put, pure antifreeze transfers heat slower than water. But, pure water freezes at a higher temperature and boils at a lower temperature than a mixture of water and antifreeze. Hence we add antifreeze to provide safety from boil-overs and freezing. However there is a caveat, a mixture of antifreeze and water where the antifreeze is greater than 50% will cause the car to overheat. When you add antifreeze, NEVER add more than to make a 50/50 mix. Get a cheap $4 plastic tester from your parts store and check the mixture before you add fluid. If the mix is at 50/50 then add more 50/50. If some of the water has evaporated and the mixture has more antifreeze, add a little distilled water. If there is too much water, add just antifreeze. And, if the mixture is old or screwed up badly, drain the engine and refill it with 50/50, being sure to follow proper bleeding procedures.
None of these will guarantee against a BHG, but if they are followed when the car is new and all through it's life, there is a lessor chance of developing a BHG than if they are not followed. When I owned a 6 cyl jeep many years ago I was not careful with the antifreeze mixture. The mixture was much more antifreeze than 50/50, and the engine always ran hot. Eventually it developed a BHG, although it was so small it didn't affect driving. Then the radiator went bad and I took it to a shop to be rodded out and a new top tank put on. I asked about some of the small deposits in it. The guy who had been in that industry for years told me that even though the radiator had been kept clean, the use of tap water had leached chemicals out of the solder and that is what I was seeing, that if I used a 50/50 mix w/ distilled water the problem would slow. The small BHG added acid to the mixture which just made the situation worse. I followed his instructions and not only did the build up stop, but with a 50/50 mixyure the car ran about 1/4 cooler on the gauge during long freeway drives or up long grades.
So here is what you can do. Get a tester and when the car is COLD check the radiator fluid level with the cap off. It should be full to the very top. Check the fluid with the tester, is it 50/50? If not have the fluid changed and make it so. Be sure to follow proper bleeding procedure, also, remember that antifreeze is extremely poisonous. Just ingesting a little can kill you in a slow painful death as the crystals grow inside your body and puncture your kidneys. Literally a cat stepping in it and licking its paw is enough to kill the cat. Also inspect the radiator cap. How old is it? If the rubber showing signs of wear? Get a new cap to replace it as the cap has a valve in it that allows air to go out and fluid to be drawn back in. If you add fluid, squeeze the top hose to the radiator a little. Does air come out? If so follow proper bleeding procedures to bring the fluid up to the top of the radiator neck. And, if you add fluid, check it again in a week when it is cold. Keeping checking every week until it doesn't need fluid, then check it when you the other fluids or change the oil.
