My2000Z28

iTrader: (1)

Just did an engine swap. Thought it was completely empty so I filled it up with yellow coolant. Turns out there was still a little dex in there. It says not to mix the two. It's gotta be at least a 90/10 mixture. Am I okay or do I need a flush and fill

Undertow74

iTrader: (45)

My Personal opinion, I would go ahead and drain it and pull the thermostat and shove a hose in there and flush it all out, and then put good coolant in it, dont want that **** to gunk up. Now with that said, did you put that universal coolant in it, or the regular ethalyne glycol?

FiredUpZ28

Yellow and dex are okay to mix, don't worry about it. Yellow is universal long-life coolant and dex-cool is GMs long-life coolant.

safemode

iTrader: (1)

I'll never trust dex-cool. Not sure if they changed the formula but when they introduced it in 2001'ish it had the tendency to coagulate and form a crust of orange crud on everything it touched. It's a horrible horrible coolant and I would sooner use oil as my coolant than dexcool. I would flush the whole thing, run some kind of coolant cleaner to get it off any internal surfaces and then start fresh.

FiredUpZ28

First off it was introduced in '96, and second it coagulates like that because no one follows the recommended flushing intervals. Its five years OR 150,000 miles, whichever comes FIRST. People go 10 years and have 90k and never flush it, then bitch when it gums up. Every single 4th gen F body on the road should have had a coolant flush at the very least once, some twice, and earlier models three times.

Mr Incredible

It probably won't hurt much to leave it and shorten your next flush interval, but you probably won't rest until you flush/fill again, so go ahead and do it when you have a warm enough day.