I have a 93 GMC Sierra with the 350. Recently the coolant in it turned into a dark red color. I drained it and used radiator flush to flush it out. I ran three bottles of it through there and followed the instructions each time I did it. I would do a bottle and add water, drive a about 100 miles, drain and repeat. I then just ran straight water for a little while, draining it out periodically until it ran clear while draining. I then put in a new radiator since the flush made it start leaking. After pouring Peak brand 50/50 coolant in my radiator and driving around to open the thermostat, I found that the green coolant that I just poured in there is now murky red. I'm aggravated because I just spent 50 dollars on jugs of coolant just for it to be ruined. Do the store bought flushes not work? Do I just need to have a shop clean it out and refill it?
what's rust starts in a vehicle it's pretty much impossible to get rid of it all it doesn't mean anything it can't corrode it that fast
but if it turns that color that quick I'd be hilarious something else like a blowing head gasket or transmission fluid mixing with the coolant because the transmission cooler on the bottom of the radiator is broken and allowing transmission fluid to mix with the radiator coolant
@scottykilmer
I just rebuilt the engine. New everything. It has maybe 15k miles on it. External trans cooler. Surely my gaskets aren't going now? I hope not...
@scottykilmer
Plus, it isn't burning amy coolant. I keep the same levels and the transmission fluid doesn't go through the radiator. I wanted to avoid that problem a long time ago, so I installed the external cooler. It runs great, decent gas mileage.