DONT USE ANY LEAK SEALERS, like bards leak. I did that ONCE:(
it ruined the heate core, plugged it solid.
this occured in early spring, garage wanted 850 bucks just for labor the dash board had to be completely removed to replace the heater core, sadly the van went to the junkyard bcause i was dumb and used the leak sealer
found the real source of the leak, a bad hose.