Hi Mopar guys and gals: Cruiser here with a cooling system question. I'm pretty particular about keeping up the cooling system in my bone stock 1974 slant six Duster. The owners manual says the proper way to change the coolant is to knock out the freeze plugs in the side of the motor to drain all the dirty coolant out. I've never done this in any slant six car that I've ever owned. First of all, I wouldn't know how to get them out or back in. And second, they're nearly impossible to access as they're under the exhaust manifold. Looks like there are four of them back there. In any case, I've been backflushing my cooling system with a backflushing tee in the 1/2" heater inlet hose for a number of years. Seems to do the job very well. But now I'm thinking that I might be trapping some dirty coolant in my engine because (I'm assuming) the thermostat is closed during the backflushing process, and I haven't knocked out the freeze plugs. There's also another plug in the right side of the block under the #5 spark plug (see photo). What does this do? Does it drain the block? So the question is: How thorough of a job does backflushing my cooling system do? Thanks.
