Actually Ive been researching this and is seems common to Toyota using distilled & toyota red.
This thread I linked to helps explain it. In my 1JZ Sc300 I personally use Toyota Red, Distilled water and Redline WW, but yet I still have this brown sludge getting created. It was almost clogging my radiator nipple that runs to the overflow bottle before I cleaned it out, but damn it could clog up the thermostat eventually or worse..
The coolant overflow had this brown soft sand stuff in the bottom..basically the FJ80 guys have done a lot of research into this and have even created a custom coolant filter system since they haven't figured out how to stop the brown sludge stuff from being created.
This shit literally turns into a brown dry powder...just read the link below and you'll see. It isn't oil and I tried the exhaust gas analysis test kit a couple times and I dont have exhaust gas being detected in my coolant as the blue fluid didn't turn yellow at all.
**on the other hand I checked my Supra and someone installed green ethylene glycol at some point, and the coolant overflow is pristine, no signs of the brown stuff at all.
http://forum.ih8mud.com/80-series-tech/96871-serious-sludge-found-overflow-bottle.html
If anyone has any pertinent info after looking at the above thread please let me know although I searched this forum and haven't found any real answer to this mystery.
**honestly, what it sounds like to me is that the Toyota Red is producing a byproduct similar to GM Dexcool(orange 100k BS coolant) Basically, Dexcool if not changed out very often WILL turn into a sand like abrasive substance in your coolant system. Most GM trucks with the plastic remote radiator fill bottle have the crap built up around the radiator cap as does my moms truck right now. Seems that it collects where coolant isn't moving much the most, but it can be suspended in the coolant at all times.
I may flush out all of the Toyota Red and just use the green ethylene glycol cause Ive never seen any byproduct shit ceated from the green stuff.
Join Date: Aug 2004
Location: Folsom, CA
Posts: 90
Ran across this post on the 80's list from a guy in Australia-
"Gday,
I wrote a week or 2 ago about my 1hz overheating up hill. From ringing
around radiator specialists, the likely cause is probably a blocked
radiator and not the clutch fan. The cruiser has only done 150k.
One bloke told me they block up with Aluminium Oxide (or something like
that) from a reaction with the engine. This is in the form of a fine
powder. His advice was to flush the cooling system with straight Vinegar
(cleaning grade). This apparently replaces the protective coat. Then
drain it and run the engine briefly. The same active ingredient may be in
thoses radiator flush products. I will also replace the thermostat just
to be sure. I will also get the radiator flushed.
Linton"
