Earlier I posted about my '83 240d that had an overheat event while my son was driving.

Bottom line, I'm pretty sure I have a blown head gasket (or maybe a cracked head). The engine runs fine, but after 5-10 minutes at medium rpm, it overheats. I have a large funnel that fits perfectly into the radiator neck. I filled with water while fast-idling the car, and after the stat opens, you see bubbles coming up out of the radiator every now and then. I believe this is exhaust gas.

Youtube is full of videos of people swearing by various head gasket leak sealers. Barrs, Bears True Blue, many others. I watched the Bears how-to video and they are quite specific on the process. It is not just dump it in there and forget it.

Have any of you had any experience with these products?