I've just flushed a system that's been running 24x7 for the last two years.
Innovatek HPPS pump + Innovatek push-on res (ABS version)
Swiftech 5002 block (anodized aluminum back)
mercury montego heater core
opaque soft silicone tubing.
10% solution of distilled water and Valvoline Racing Coolant
Everything looked good. A very thin layer of grey or white colored deposit inside the res. Didn't seem to be inside the block or inside the small length of hose I split open to examine - maybe just built up where the coolant slows down.
Pump internals looked pretty much new
Nylon barbs on the 5002 has soaked up a little of the VRC pink dye
Buttoned back up, refilled with distilled water and 5% VRC (I'll know in another two years whether the 10% was more than enough...)
Note - I'd given the owner a couple of bottles of DW/VRC at 10% mix. (silicone hoses lose water a bit faster than vinyl, so there's a need for bi-monthly top-up). If the walls of the silicone tubing are working as some sort of osmotic filter (i.e. water goes out, VRC stays) it's possible that the concentration has been going up as he refills). He'd gone through about a pint (
if we both remember correctly how much I gave him).
Oh - and the piece of foam I'd put under the pump/res combo to damp any pump vibrations before they got to the case had gone almost completely flat.
[edit] changed Innovatek push-on
rad (ABS version) to Innovatek push-on
res(ABS version) ... duh![/edit]