Vehicle: 2005 Toyota Corolla - 1ZZFE with 229k miles when I purchased it, now it has 231k miles.
Background: the vehicle was in excellent cosmetic and running condition, the valve cover gasket had been leaking for a very long time, and the engine was covered with the oil leak, I cleaned it up and changed all the rubber gaskets I could think of.
1 owner vehicle with oil changes done every 3-3.5k miles at Valvoline instant oil change place, which was obvious with the oil being spilled all over at the oil fill cap and the oil drain plug was completely missing a gasket...
The engine was well maintained and doesn't burn any oil and I have taken it on two 600-mile round trips at very high speeds, although the oil color is not an indicator, it was very clean inside the engine and the old oil stayed fairly clean when I changed it at 1,500 miles since the previous oil change from Valvoline instant oil change place.
Completely neglected maintenance:
1) Automatic Transmission - I did a transmission pan drop with a filter change and then exchanged the fluid from the transmission return line from the radiator until cherry red fluid came out and I ended up using about 8.5 quarts of Prime Dexron II/III ATF w/ 10oz Red Lubegard bottle. It shifted perfectly before and still does now. I have personally done this on 40+ Toyota 4-speed ATs with zero issues and have used various ATFs with no problems, including the combo I used for the last 10 Toyota 4-speed ATs.
2) Power Steering Fluid - I did a complete flush using the return line and used Maxlife ATF to slow down or prevent any future leaks, and after 1,500 miles it is still dry and functions perfectly. It used to whine a little before at full turns.
2) Coolant - OEM pink factory coolant that was still full, I'm assuming it was topped off - I did a drain from the radiator, removed the thermostat, and drained the coolant from the drain union on the back of the engine block, got out as much as I could and it came out pinkish-red. Replace it with Prestone Cooling System Cleaner and distilled water, and it came out orange as shown in the second first after a 600-mile round trip at high speeds. Everything seemed good so far, and I was assuming it was going to continue to drain at a lighter color each time until almost clear distilled water would come out and I would simply add full strength coolant at half of the cooling system capacity and be done with it.
the 3rd D & F came out black colored and the 4th D & F came out a light black color, I got concerned and put the car in the air and try to rev it at different speeds to see if there as possible failing hoses or leak and I revved the engine to 4-5k and kept it there for 3-4 minutes and the engine sounded very smooth but then the 5 D & F came out looking like the 3rd one, and the 6th D & F came out a light black color.
1) 1st drain came out pinkish-red - Original Coolant
2) 2nd drain came out orange - Prestone Cooling System Cleaner(1st time using it) with Distilled Water after a 600-mile trip at high speeds.
3) 3rd drain came out black - distilled water added
4) 4th drain came out light black - distilled water added
5) 5th drain came out black - distilled water added and the engine was revved to 4-5k RPMs for 3-4 minutes (while lifted off the ground on jack stands)
6) 6th drain came out light black - distilled water added
The car is driven around to make sure the thermostat has opened and the coolant has fully circulated between each drain and fill.
I washed the drain pan to see if there is any residue left behind from the black-colored liquid, and it is leaving behind a mostly white and slightly black-colored powder residue.
what could be going on? The car doesn't overheat and doesn't have any external leaks anywhere. I would greatly appreciate any suggestions, I would be doing more drain and refills this weekend to see if it gets more clear.
FYI - I have used Peak Coolant Flush 40+ times with subsequent distilled water drain and fills until clear liquid came out, I used to be an engine rebuilder, specifically the 1zzfe engine and I have never ever seen this before.