@ssanmor

I use MB coolant and distilled, about a 40/60 (antifreeze/water) ratio. I've also had positive results
with RedLine's "WatterWetter" product, of course YMMV.

If it's been a while, or you suspect it's never been done, now's probably a good time to replace the thermostat.

@all

Any comments on tap water (or filtered tap water) vs. distilled? I've always used distilled, with the thought
that mineral deposits from tap water are a negative. (Especially after seeing a few very corroded MBs.)