Did a thorough coolant flush about 3 months ago to switch from Preston Extended Life back to BMW blue. Put in 50/50 mix and a half bottle of Redline Water Wetter.

Popped the bonnet to check the oil today and noticed the coolant is starting to turn from BMW blue to black. In the past as the coolant has deteriorated it's turned more of an orange color.

No sign of coolant in the oil and this doesn't really seem to be oil in the coolant, so I don't think it's a head gasket.

Anyone else have this happen? A quick google search seemed to point to the water wetter as the culprit. Didn't happen the last time I used it, but the last was with Preston Extended Life coolant, not the BMW stuff. Maybe it just reacts differently with BMW coolant.

 

looks pretty normal. its not sludgy is it?

 

No sludge as far as I can tell - might try to drain the reservoir tonight to get a better look at it and compare to fresh side-by-side.

I agree, it doesn't seem too bad, but it does seem to be getting more black than when I first put it in 3 months ago.

 

Sifted through some old pictures and found one from replacing my valve cover gasket that shows what the coolant looked like about 2 months ago - definitely bluer.

Something's going on with it, but it's hard to say what at this point. Will probably try a thorough flush and refill first when I get a chance.

 

My guess is that is the color you get if the preston was green/orange and then you drained and put in the blue... you will never get all of one type of antifreeze out...so you end up with that color...best thing to do is change it again.. but I don't think you have anything wrong..lol

 

Good point. I flushed it with distilled water what must have been 8-10 times and it was coming out pretty clear after that, but it probably still had some of the Preston left. There were also probably trace amounts of the cleaner I used too (Gunk C2124).

Guess I'll be flushing again soon...was hoping I was set for a few years the last time!

 

If you flushed it with water...do you mean you just rinsed it through or did you run the motor for a bit?

 

Ran it each time for 5 minutes or so, so the water would mix with whatever antifreeze was left. The whole process took what seemed like forever for it to start coming out clear.

 

I know...it does seem like it takes forever... My bet is that you got the majority of it out but there were pockets of the other antifreeze that never circulated.. like the heater core... So you did it correctly.. I would just change it again if you feel up to it.. other then that I think your car is fine.. I had the same thing happen to me back when I changed from one color to the other..then went back to the blue.. Im going to stay with the blue from now on ha ha...good luck !

 

Yeah, I'm sticking with blue from now on too.

Here's to hoping another round of flushing clears things up. Might get to it this weekend...