Stop leak products that contain metallic powder such as "Silver seal" can and do clog up radiators. I once pulled a radiator from an old Ford van that must have weighed 15 pounds more than the replacement one we installed. We pulled the bottom tank and found it was completely full of aluminum powder. Vegetable fiber sealers like Bar's Leaks don't clog things up under most circumstances, but anything can be over-used.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!