M42 coolant

[bmwman91]

Tap water is fine for flushing things out. The corrosion issues that the minerals in it cause take YEARS to manifest. An hour of flushing is no biggie. You will need to flush it a few times to really get all the old shit out. Most of it is usually stuck in the thin passages in the radiator, so if you could remove it and hook up a hose to the outlet, turn it on full blast and the crud should come out the inlet. It is probably a non-issue really. The M42's cooling system was a bit too large for the engine in the first place and cooling is really only an issue if you track it or live somewhere super hot.

In fact, tap water is generally fine to use, period, because any half-way decent anti-freeze on the market these days has corrosion inhibitors. DI water is cheap as hell though, so the $0.99 a gallon of it costs isn't really a big deal.

[roguetoaster]

When flushing the radiator the best quick and (essentially) free method I found was to pressure wash the inside with the radiator on sitting each side, upright, and upside down. Alternate water inputs from each large plastic inlet/outlet as you go. The blobs of brownish goo that came out of mine on the upside down pressure washing were impressive. I suppose you could use a pressure washer on the coolant passages on the engine, but I have yet to try it.

It's also a great time to clean off those fins to extract maximum heat dissipation.

[TobyB]

is there anything wrong with running it for a few minutes with water in order to flush it out??

also does anybody know how much coolant it takes?

Nope. Distilled water is slightly better. Open the block drain for even more win.

Just as long as coolant goes back in, (1 gallon coolant, a little under 1 gallon water)
you are totally fine.

Turn on the heater while you're doing this!

t

[salvuhdor]

soooooooo.... I should just grab my garden hose and stick it in the radiator hole and then loosen the bottom screw to drain it out and clean it a bit.. while the car is running then after a while when no water is pouring out I should then seal everything back up, tighten the lower screw and pour in my BWW coolant?

[MF DOOM]

lols

I use g05 in my m20

No, im serious. If its an aluminum black then go ahead and use distilled water. Or dont... I end up draining my coolant at least once a year for various reasons anyways. None of them having anything to do with corrosion though.