Block seal is the single worst thing anyone can ever do to any engine they care about.



That being said, the heater problem you described sounds like a blocked line somewhere. Couldnt tell you where.

 

that block seal stuff has a tendency to clog up heater cores, even on brand new cars. doesnt always happens. but every now and then it does.



your main thing should be figuring where the coolant is going.



kevin.