I had a leak in my radiator 8 months ago. For a month after replacement radiator I had heat. Then replacement radiator sprung a leak. put in Barge super stop leak which fixed leak,but no heat.Put in super flush after I took out thermostate.I drained out flush but broke neck on radiator which I replaced. I put in new thermostate and new radiator cap,still no heat.what is next to have heat.Trooperdog.
Feel the inflowing and outflowing hoses on the heater core. See if the coolant is even moving through the core.
If not, the stop leak has also stopped the flow through the heater core as well as the leak.
If it is flowing, then the stop leak has coated the heater core insides to where it’s having difficulty transferring the heat from the coolant to the air sufficiently for your needs.
Listen to the same mountain bike he knows what he is talking about. Is the heater valve manual or electric? most are manual, and you can check to see if the linkage is connected and working. If it is electrical, make sure the wires are hooked up, and test if for operation. Are the hoses soft? sometimes radiator hoses and even heater hoses collaps due to material fatigue. If all this is good, then take out the heater core, and use a hose to flush it out. If you cannot get it to flush out, you may have to replace it. This is a one of the those jobs I like to call under-dash-aerobics, your back will get a real work out fixing this one. good luck
One thing I forgot to tell you is when you take out thermostat you have all kind of heat as long as you are sitting still. When you put the thermostat back in you have no heat. I had no heat before I put the the sealant in.