In my Bonneville owners manual (1992 SE) it says that when flushing coolant system and replacing coolant a sealer supplement - GM brand or equivalent - is recommended.

Anyone out there ever add any sealer when replacing system with new coolant? I used Prestone'* bottled sealer a few years ago and had all kinds of goop particles floating in my radiator which made it look really SUPER dirty and difficult to measure with a coolant tester.

Haven't used any sealer in a while but the Ponitac parts guy recently recommended purchaing the GM sealer tablets as part of preventive maintenence. Any suggestions?

Well, If it ain't broke......
I personally have NEVER added any of that sealer stuff when I replaced the coolant. Why gum up the works? And if you do develop a leak sometime down the road(like a hose or water pump for example) all the "stop-leak" in the world is not going to solve those problems. I gotta admit, a long time ago I owned a 67 Chevy Nova. The radiator developed a pin hole leak while I was on a trip. I poured in some of those aluminum filings. And it did plug up the leak so I was able to get home with the car. I'm not sure if I would do the same with today'* engines.

I think those filings wouldnt hurt anything because as soon as the car hits 200-10 the alum is going to soften then when you shut the car off its going to settle and adhere to what? Aluminum so I think its not the worst thing in the world.

I recently added some of that to my coolant (stop leak that is). I had a hairline crack at the end of my rad and really didn't feel like replaceing the whole thing. I no longer leak coolant and everything is functioning normally. It'* a lot cheaper than a whole new rad but I just hope it lasts.

Use it at your discretion, I have heard horror stories, Gordy... my fingers are crossed for you bro.