I’m having trouble with my 96 blazer it’s pours out coolant when heater is running when it’s off it doesn’t is this my heater core ? Please help
Do you mean the coolant flows out the bottom of the engine compartment and onto the ground when the heater is running? I’d guess that’s a problem with the heater return hose rather than the heater core. A leak in the heater core usually pours water into the passenger compartment. Suggest to check the floorboards under the carpet, make sure they aren’t wet as a precaution. The heater return hose connects at the firewall in the engine compartment, and runs to the engine somewhere. Be sure to keep the coolant in the radiator topped off until this is resolved.
S-10 blazer, I presume?
In other words, the small one, with the 4.3 liter V6 . . . ?
You better hope it’s the heater hoses, and not the heater core itself
Because I seem to recall replacing the heater core is pretty involved on this model 
I’m seeing 5.5hrs labor time, which would confirm what I said . . . big job
Follow George’s advice . . . check WHERE the coolant is actually coming out, and check that passenger compartment very well.
Water is not on my floor board and shoot out when I run the heater
So it wouldn’t be a freeze plug would it?
If it is coming out that fast, it should be easy to spot.
Possible, but unlikely if it only leaks when the heater is turned on. A freeze plug would leak all the time. Unusually when a freeze plug leaks it sort of dribbles, doesn’t spray coolant. First guess has to be somewhere between the firewall where the heater OUT hose connects there, and where the heater OUT hose connects to the engine.