Considering your climate, you can get away with doing just water. Please don't drag it on for so long that you end up only running water as it has no properties to stop any potential rusting. For example, I run distilled water and Water Wetter in my bike since it stays in a heated garage and doesn't get run during the winter season. NO TAP WATER, only use distilled water, it's a measily $1 for a gallon. As for repairs, you might not want to hear this, but piece mealing the M62 cooling system is a no no. Be prepared, literally, to replace everything...radiator, thermostat, waterpump, expansion tank, valley pan gasket, hoses, BMW/Zerex G02 coolant, distilled water.

On top of owning two BMW's with M62 engines, I've worked on and been involved with COUNTLESS people who tried to essentially halfass repair the cooling system on these engines. It doesn't work, because as you replace one new item within the system, it just puts more pressure on the older remaining parts, so when they break, you'll be back on the side of the road doing it all over again. Also, bleeding the cooling system on this engine is critical, so even what you're attempting to do now with just topping off and continuing to drive the car is the epitome of a bandaid fix. If you need this vehicle, you need to replace these items asap before it snowballs into more. This may sound like scare tactics, but I've seen more than most poeple as to what can happen when people take the shortcuts.

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