I changed coolant 6 months ago. Now there is some light brown crystals or mold growing at the top of the waterline where the coolant has evaporated.

Perhaps the coolant pump is broken and stopped circulating, so the liquid just remained stagnant? Is it possible for my engine to run like that for 6 months?

On my own, I can get some long qtips and scrape them out, then change coolant again. But I'm wondering, is there a standard procedure to correct this?

Maybe the pressure cap or return side aren't working.
Have you asked a mechanic what the brown stuff is?

Mechanics do not work on Saturday.

I will lubricate the rubber on the pressure cap, then check to see if I can see the coolant spraying around in there. Is the coolant continually circulating upon engine start-up, or does it turn off and on depending on the temperature? Last time I changed coolant I saw that it was circulating, but then again it was very hot outside.

Tomorrow I'll head to the auto hobby shop where they have vehicle lifts and hopefully take care of this.

Good luck with the fix.

What type of coolant did you put in? Flush it out with another brand.

You will find crap like that in almost every reservoir, it's just oily crud from the grease on the waterpump and inside cooling passages..

The tank is the highest point in the system, if it will float it will collect on the surface there. The return to the rad is off the bottom of the tank, so once it gets in there it stays.

You could clean it out if it bothers you, but it's not a "problem".

S

Ok, it's not a problem then.

On the way back from a drive, I opened the hood while running, and got to see the top hose flowing coolant into the reservoir. I guess it usually doesn't turn on during the engine warmup process, only after some hard driving.

http://www.underway.us/rx8/coolant/brown.jpg

http://www.underway.us/rx8/coolant/prestone.jpg