Pull Engine Block Drains When Changing Coolant

It is important to remove the engine block drain plugs when changing coolant during routine maintenance. I learned this the hard way due to cooling problems on my 428 Mustang. Over many years, scale and other deposits can build up at the bottom of the engine block and restrict coolant flow in the water jacket around the bottom of the cylinders. This can lead to uneven cooling and overheating. While I encountered this on my 428, it applies to most engines. My 3rd Gen Camaro 305 has the same type drains in roughly the same location and even though I have a fresh clean block, I will remove these plugs at every coolant change for prevention. The right hand side on mine actually has a knock sensor threaded into the drain hole.

IMPORTANT NOTE: "Block drain plugs" refers to the pipe plugs or other fittings provided in the engine for purposes of draining the water jacket. These are NOT the core plugs, commonly referred to as "freeze plugs" that are sheet metal type plugs pressed into the openings in the casting. Those plugs should not be removed. If you are not sure, check the service information for your particular engine to locate the correct drains. Each engine design is different and may have different type plugs, or methods to drain the block.


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