I recently siphoned out about 3 liters from the 92' in preparation for a fan clutch swap. The fluid had time to sit in a clear bottle over a few weeks and what I found was a thin layer of super fine material which appeared to be a rust color (in green coolant). During that same time I was at my local autoshop hanging out while my wife's car was worked on. I watched the crew change the radiator filter on a tow truck, and a light bulb went on in my head. So I turned to mud and found this thread.
after thinking it over, I do not think it is worth it for me to install a permanent filter. However, having had worked with live fish for many years (aquarium/aquaculture) I would like to offer a suggestion for mudders interested in clean rad fluid. If an aquarium was super dirty we used to bring along a setup on a dolly which consisted of a strong pump, a canister filter, and a UV sterilizer. We ran it temporarily to clear up the water of toxic blooms/suspended sediment etc, and sterilize. This system could easily be applied to filtering a radiator (no need for UV), without the need for permanent install of filter media. Here is what I reccommend:
1. setup 2 ports, one for fluid in, one for fluid out (autozone Ts would work, or maybe somehow on rad fill opening)
2. purchase an aquarium or other pump (home depot, Amazon, Harbor Freight, etc.) I would reccommend atleast 1800 GPH to handle the head of passing fluid through the engine (Danner mag-drive are excellent)
3. purchase a canister filter, pleated filter media (the smaller the micron the better, I would go sub 100), and necessary plumbing/hoses/clamps to match filter, pump, and access ports (3/4" would be good, any smaller and your pump will have to work too hard). these can also be purchased at the above places, and all the same stuff is basically used for aquariums and home water filtration systems. Automotive filters likely just differ in their temperature tolerances
4. Setup a closed loop on the cooling system and flush away. Run vehicle a little, might help stir up some junk-but do not run too long might get too hot for pump. Rinse pleated filter in a bucket to capture fines-if your curious.
I plan on trying this in the near future and will report back. This could be done as part of oil change routine, or as you see fit. Also: air locks may occur (no flow) which can often be remedied by shutting off the pump and burping the system. Dont forget to prime the pump-
Cheers,
RG