The 7 gets much love from 2nd owner - coolant flush (rainbow pic)
 

After 18 gals of distilled water....

https://cimg2.ibsrv.net/gimg/www.rx7...21f3797462.jpg

WOW. That was SERIOUSLY overdue!

I recommend everyone change coolant out once a year. Doesn't take much time or cost much but makes a HUGE difference.

Dale

Jeez I’ve bever seen coolant that dark

I've been changing ~50% of mine every year - I drain the radiator and refill with 50/50 green AF and distilled water. That way the anti-corrosion additives get replenished every year. I've been doing that for ~20 years now on both the FD and my '74 Chevy Van that is my F2000 racecar's tow vehicle. Doing it this way is very quick, easy, and seems to be effective. The coolant always looks new when I drain it.

Nice!

Yeah, I've never seen black coolant before as well. Later down the road will change out the radiator. The car has 41k miles and I don't think the coolant has ever been changed.

Lol
 

Unless he used prune juice for coolant

I just flushed my system with Thermocure, which is a chelating agent that binds iron(rust) into solution, and it turns black just like this. It did make a difference in cooling efficiency. Likely cleaned some of the old corrosion and rust, particularly for the side iron cooling channels on my 15 year old keg.
Mike

Looks a lot like mine but you got a better pic :)
Took me 14 gallons
https://www.rx7club.com/3rd-generati...lushes-977577/

Oh geeze. I've gone through ~10 gallons and mine is still coming out pretty dark. I've never seen a coolant system as mucked up as mine was though.

I think I’d rebuild if my coolant was that dark, I’m so paranoid hahaha

I forget now who it was here that convinced me, but since my coolant seal failure 12 yrs ago I've been changing it out annually. Part of my spring coming out routine...scheduled for this week.

That'll make your tailpipe raw.