I recently put a can of seafoam in my gas tank because my mileage had been dropping.Recommended is one ounce per gallon and I think I actually put almost two. Soon after engine was sputtering bad at startup. The check engine light came on and on my way home from work my high temperature light came on at the traffic light. It went back out after a few seconds. Went home and noticed low coolant, Filled it and the check engine light went off on my next trip home from work. Started up again for work and more sputtering and the check engine light came back on… By now I filled the tank up with fuel. About 3 days later the hot engine light came on again on my trip home about 3 times. I turned on the heater full blast and that kept the engine cooler for the rest of the trip. I pulled and repaced the plugs of which one electrode was severly worn. Otherwise the plugs were a little white from the hot engine. Compression is 152 on the 4 cylinders and no visable leaks. It looses about one cup coolant every round trip (120 miles). It never steamed as an overheated engine sometimes does. I can’t think that a head or intake gasket would blow for the temp light coming on a few seconds at a time. I changed the thermostat but that didn’t help. Does not overhaeat any more and the check engine light stays off but just uses coolant. Does have some water and white smoke out the tail pipe at start up but after reaching temperature its dry and clear.
I doubt the Seafoam had anything to do with your problem. Sounds like a coincidence. I would have the cooling system pressure tested and examined for combustion gases. Also, how does the oil look? If you didn’t have a head gasket before you overheated, you may now.
There’s nothing you can put in your gas tank that can make your engine lose coolant and overheat. The Seafoam had nothing to do with it. If you’re still losing coolant and can’t determine the cause yourself, have the car checked out before the trouble becomes worse.