Two problems related to manifold/header/muffler/tail pipe have been reported for the 1999 Chevrolet Blazer. The most recently reported issues are listed below.
After having driven the vehicle for about 2 hours on interstate roads (constantly monitoring the coolant gauge - standard for any trip I take). I stopped to go to the rest room and when I returned and started the vehicle it made a horrible loud metal banging noise. I moved the vehicle to that if it needed to be towed it would be ready. I checked the coolant gauge and it was at the very end of the hot zone, checked the coolant and found almost no coolant in the reservoir. I had to put water in to get it home (another 3 hours on the road). At no time during that trip did the coolant gauge indicate that the vehicle was overheating. I have changed the oil per the recommendation in the owners manual and have done most of the other recommendations and have had no other major issues with the vehicle. On July 12th I had the manifold intake gasket replaced, oil changed and tires rotated in preparation for the trip.
Contact took vehicle to a mechanic for an oil change. They checked the fluids, and found the manifold gaskets leaking. Repairs were done at the contact's expense.