There is a product on the market that is having excellent success with sealing a leaking head gasket K&W engine block sealant I have heard several reports of successful sealing of head gasket leaks as to how long they will last the jury is still out-Do not follow the instructions but instead. Flush with clear water drain all fluids from the engine and radiator this works best if you use some type of extraction system. Add the product and top off with plain water. Drive for 500 miles being sure some of these are highway miles but without to much of a load IE no long hill climbs. Refill with the proper AF mixture for your area and road test wouldn’t hurt to stop by the church for a little help. Actually you will probably before this as the leak should stop before the 500 miles. Remember the engine has no freeze or overheating protection during the 500 miles. Good Luck I have heard of some excellent results using this method.