I have coffee filters  in my shop that I use just for this purpose.
After a short time it will get clogged and slow.  You will
need to sift the coolant, but eventually replace the filter
a few times.    Does and good job, but takes some time.
Therefore I'm sure the average corner garage will
just as soon put new coolant in, and charge you a ton.

Jeffrey Lubin wrote:

> I was draining some coolant today and accidentally got a little bit of
> dirt in it.
> Since I'd like to re-use the coolant, I was thinking I'd strain it
> through a coffee filter.
> Is this a really silly idea or what?
>