Coolant Leak Sealer for 3.5

99 Intrigue with 3.5 has slow coolant leak at crossover. Would like advice on use of a coolant system sealer and what specific sealer to use. Car has 215XXX miles on it and otherwise no problems

replace gaskets, do no use stop leak. It will plug everything up, and cause more problems down the road.

replace gaskets, do no use stop leak. It will plug everything up, and cause more problems down the road.

Agreed. Have seen plenty of heater cores plugged with the stop leak stuff.

I have had really good luck with AC delco Seal Tabs.
They are like TUMs for your car.

If the coolant looks dirty you should change it. Dirty coolant is usually the cause of clogged heater cores. I've never had the seal tabs cause an issue.
I've used them on GM, Ford and Subaru. The Subaru was so bad it was actively dripping and it has been years without an issue.

Yes, changing gaskets is the best repair, but since you are asking, I doubt you will be going that route.