Low Coolant & Debris Inside Reservoir

[Dave C]

Background: 2004MY 3400 engine with ~58k miles

So my low coolant light blinked on about two weeks ago, and turned off maybe 15 seconds later. I checked the level, and it was just above the top of the hose at the front/bottom of the tank. There was also some debris inside the overflow area of the tank (like little flakes of something). I've had no problems during driving since then because I was too busy with school to mess around with it. Today I checked the level, and there was a little in the reservoir, but it was almost empty (there was a little at the bottom, but that is all). I also searched on here for a while to try to find the answer, but wasn't successful. Now, I am about to get a ride to go buy some coolant to fill it up to the normal level...

I am wondering what could be causing the debris in the reservoir?


---edit---
I also checked the oil, it is the normal brown, and about ready for an oil change.

[rixGAphx]

This is prolly the original orange 'DexCool' coolant.
The mixture should be about 50-50 DexCool-distilled water.

It's pretty normal for a 4-yr old cooling system to be looking a little brownish, and mebbe have some tiny flakes (about 1/8 inch) of minerals, a slight cloudiness, as well as a *little* oily-looking scumminess on the top.
This increases the more you have used tap water (with calcium and other minerals in it) for topping-off over the years.

The entire engine block is raw iron on the inside; one purpose of antifreeze is to reduce oxidation (rust) of the iron, by reducing the contact of oxygen (dissolved in the water) with the iron.
Nonetheless, some rust occurs and so does some deposits of calcium.
If they are lighter than water, they eventually rise to the reservoir.
Just skim-off what you can, and don't worry about the remainder.

Go ahead and top-off with DexCool/distilled water, to a point 1" below the bottom of the filler neck.
The coolant needs this 1" airspace to expand into as it warms.
Only tighten the cap as much as an average woman can easily do one-handed; any tighter and you risk distorting or damaging the delicate rubber sealing washer that maintains the 14 psi pressure seal.

Good luck,
-Rick

[Dave C]

awesome, thanks for the great explanation Rick.