So I have been struggling with getting my car to blow heat. Engine temperature is normal. It has an OEM rad, no leaks. I’ve put in 2 new thermostats in the past month just in case the first one was faulty. The system is bled properly, it doesn’t overheat. Heat is ok when I’m driving, but if you put the blower past 2 its cool air again. Also if the car is at idle the air goes cool. All hoses get HOT other than the bottom heater core hose. Also the knob that goes cold to hot is very stiff. So I figured maybe the valve to allow hot coolant to the heater core wasn’t in the correct position so I moved the rod so it is in the correct position, or what I think is the correct position, but there is still no change. Had to drive home the other night in -30… So I’m dying to get this fixed. I have a garage to tear it apart too I’ve just run out of ideas. Any help? Thanks.
If one of your heater core hoses is hot and the other is cold you have a plugged heater core.Disconnect both inlet and outlet hoses and put your garden hose to them do it both ways to try and move the blockage.If this doesnt work get some CLR mix it accordingly and fill your core with the mixture.Let it sit for say half an hour or so and try flushing it again.Hopefully you’ll see a bunch of stuff come out,That’s a good sign btw.
If this fails you’ll need a new heater core.
Once you get good flow through your heater core your heat should be good again.If you still have to rev your engine to get heat you may need a new water pump or have a blockage somewhere else as well.Flush the system with the hose while you have everything disconnected just to be sure
Good luck hope this helps!