I bought a used 97 F-150 with a 4.6 v-8. The radiator coolant looked green but had a brown tint to it so I had to flush it. I first drained the coolant through the pet**** and then pour a can of flush and added water and ran it for about 20 mins. After that, I drained the pet**** and topped it with water and ran the engine for about 5 min. which in turn the plastic tank would bubble and suck the water into the engine. Afteward, I would turn the engine off and drain the water through the pet****. I repeated the procedure until the last draining the water came out clear. I would drain the coolant into a bucket so I can see what color the drained liquid would be. The is not the fastest procedure, but I didn't want to remove the drain plug in the engine, because an allen wrench was very difficult to turn in such a tight space.

With the water left in the engine, all I needed to do water use coolant straight to acheive a 50/50 mixture. During the draining phase I could tell the coolant was dirty because the coolant would tight from a dark green to a light brown then clear.

Total procedure took about 4 hours because I left it drain alot of time. But I'm sure my engine would be better for it now.