Chevrolet Repair: Red colored antifreeze, radiator cap, antifreeze

Question
Mark,
My girlfriend had someone service her car sometime back and they put a different antifreeze in her radiator. She had a redish color maybe it was called Dec-cool or something like that. Anyway her coolant has almost turned to a sludge.
Question: Can I flush this OK myself or do I need to have it done professionally. I am real concerned that it is going to cause some damage.
What type antifreeze and be used given that it had this red type to begin with.

Thanks so much

Answer
Hi Finley, Yes you can flush the system your self. I would use the old style green coolant if it was my car. I really don't like the dex cool coolant. You my have to flush the system morethen one time. Before you add the new coolant I would take it for a 45 minute ride and then check to make sure the water is still clean when you get back. If it is drain the water and add coolant. If not...flush again.
Replace the radiator cap too.

Hope this helps

Mark