5 days since 2nd installation using 7 lb pressure cap. No leaks, no seeps, or coolant loss.
Changing from partial thumbs up to thumbs up on the following product. Worth a try. List price is $13.??.
Mendtite, cooling system sealer, heavy duty. Manufactured by Zecol Products Company, Medina, MN 55340. Available at Federated Auto Parts, and probably other locations.
Radiator stop leak for Cub thermosyphon system. Installed the above listed product in a Cub 154 Low-Boy with multiple minor and major radiator leaks. Radiator didn't leak until I removed it from tractor and flushed it and the engine block. Two radiator tube were open at the top, never soldered to radiator tank.
Filled radiator with tap water. Started engine, let warm up to temperature, topped off radiator, installed product. Replaced radiator cap with 7 lb cap. Let engine run for about 1 hour.
My first attempt with this product left a couple of small seeps after setting for 2 or 3 days. I didn't use a pressure radiator cap on my first attempt.
I have an excuse. CRS.