Water alone will provide most of the cooling and heating required.

A couple things that are quite important:

The most important factors of coolant are that it won't freeze so it won't expand and break the engine but also that It prevents corrosion. Water alone will corrode aluminum or iron engines especially with the heat.

Then, it's crucial to never put tap water in your engine as the disolved solids will cook themselves to the inside of the engine.

Get the leak figured out. Stuff some paper towels where you suspect the leak is and where wetness forms there ya go. Some leaks when slow enough won't ever drip they evaporate first but once paper towel becomes wet it's permanently changed in texture so it's a good tracer. The reservoir tank is the most common leak source.


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2011 E70 • N55 (me)
2012 E70 • N63 (wife)