Sorry Evercool but we beg to differ.

[dr. d]

"Grounded", in colloquial terms refer to stray electrical currents that lead to electrolysis.

If only to be more accurate, your if engine is improperly grounded you're going to end up with an anodic process going on between different metal parts.

"Grounded" can be a good thing or a bad thing, depending on what we are talking about.
i am confident that the gasoline engine won't run if there are no electrical currents running thru it, as measured by the multimeter..
perhaps what you mean is, the engine should be well-grounded, to avoid electrolysis from stray currents..
heck, when your engine is poorly grounded, the radiator is going to be the least of your concerns.. a poorly-grounded engine won't run well, won't charge the battery well.. it might even interfere with the electronic entertainment systems (heaven forbid!)..