No Heat

[Pro1914]

Hey all. I recently bought a beautiful one owner Burgandy 1987 325. As you do with a new E30, I figured I'd change the timing belt, water pump, thermostat, etc etc. Everything went swimmingly until It came time to start and bleed the system. The hoses all got hot except the heater core hoses. Both the top and bottom ones were ice cold. I let the car get up to idle temp, had it on an incline, bled a whole lot of air out of the system, had the heater on full, and yet nothing.

The temp kinda sorta went past 1/2 at idle, but not far enough to cause panic. I noticed even near where the heater core hose connects with the thermostat that the coolant was cold. The other hoses plugged into the thermostat were warm except for the one that plugs into the back of the thermostat housing on the driver's side. When I originally removed the thermostat, the entire thing was caked in green rocks/crystals, but I made sure to scrub the thermostat housing clean. The thermostat itself was replaced. I didn't notice the debris anywhere else in the system.

Could this just be the case of a defective, stuck-closed thermostat? Would the heater core still be cold with a stuck thermostat? If not a stuck thermostat, is it safe to drive on a car with no heat? Doesn't the car need to flow through the heater core due to it reconnecting at the back of the block?

Thanks so much for any info!

[Westija]

Your new thermostat could be defective. If so, your engine will certainly overheat, so if you let it work a while and the temp is above normal, you will know, assuming the rest of the cooling system is fine. Don't let it overheat.
You can also remove the thermostat and test it by placing it inside a pan with boiling water and observing if it opens.
But before all that, you may want to give it another bleeding just to be sure.