Alright so i was doing a quick coolant flush and fill and decided (once again) to try and clean the coolant reservoir. Last time i did the flush i hit it with bleach, brake cleaner, dawn, and just about everything else i have to get it clean. nothing even touched the gunk and black crud in there except for wiping it by hand. Now i dont know about all of you but my fingers only go in there about 2 inches, then the rest looks like ca-ca still.
I read up a few places online (mainly euro-restoration sites) and came to a few conclusions...some people use sand, some use coffee,I decided to try cat litter
so i dumped about a cup of kitty litter in the resov and sprayed the inside with a bunch of brake cleaner. shook it for abut 2 minutes and voila! super clean inside!
A little acetone/heavy cleaner on the outside and it's nice and clean.

I wish i had taken a few pics of it before, but i honestly didnt expect it to work this well. i will post up some after shots when i finish it.

Kinda hard to take a pic of how clean the inside really is.

Ok so powerful chemicals like brake cleaner and bleach didn't do anything but throw some kitty toilet in there and its magic?

Anytime I had to use cat litter to soak up anything, it turned into something more disgusting than the original mess. Is there a certain type and mixture to it?

no magic to it. the abrasiveness of the litter scrubs the oilly gunk off the walls of the resov.
I used just a handful or so of litter and soak the litter/walls down with brake cleaner. dawn may work too, but at a slower rate.
as long as you keep shaking it up the litter doesnt clump up. then dump the stuff out and wash the tank out with water.

after i re-installed it full of coolant. (35/60/5 mix: 35% antifreeze, 60%H2O, ~5% water wetter) I dont recommend that mix for anyone that see's freezing temps.

Floor dry would probably also work then, it doesn't clump up since it's just bentonite and doesn't have any of the odor killing or clumping agents that kitty litter has added to it.

great job! gives a whole new meaning to the saying "she purrs like a kitten"

Thanks for the tip. I tried cleaning mine out last fall after a coolant flush and didn't have too much success either.
Now i just need mine to purr like a kitten.
Only problem is all I have is Speedi-dry, same thing without the perfume.

Good job Matthew
I've got a couple that need some work, I'll have to give that a try the next time they are removed.