Originally Posted by fotofan
Personally I'd probably replace it (what's $25 when you're doing a T-belt?) but you could get away with leaving it. Just make sure it stays clean.
More like $50 because you're going to need about 1 1/2 gallons, but it's up to what you think will be safe. If you don't think you can keep your coolant free of contaminants while you do the work, just replace.