There is actually a drain cock on the far left part of the radiator near the corner (when facing the car) but it is not your typical plug so it might be hard to find unless you're looking for it. It is easy to break so be careful if you find it and decide to drain from there. Most people do just disconnect the hose...have to be careful replacing the hose too as the connector to the hose is hard plastic and will break if you really wrench down on it. Once you drain the coolant, just replace the plug or hose and refill. No need to worry about air bubbles, just fill about 6 to 6.5 quarts/liters of the mixture and let your engine run and the level will drop. Add more to the expansion tank and keep repeating the process. Just remember that it takes approx. 7quarts (to guage how much you should add). Also, this means that if you buy a gallon of the Volvo stuff and mix it 1/2 with distille water (highly recommended) then you will still not use all of the mixture...should have about a quart of the mixture left over. If it's never been drained, I would recommend running a hose into the expansion tank and letting water drain through the system until you see clear water coming out before refilling it.
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1998 S70 T5 Emarald Green Metallic, 2004 V70 2.5T Ruby Red, Previous Owner of Black '94 850 Turbo Wagon. My cars have been running so well lately they've got me worried.