Last winter my wife's 04 r50 with only 50k miles heat gradually started to vent cool air. I have read a lot of threads about clogged heater cores being the main culprit. My question is there a way to check the heater core without draining the coolant? I ask this because in this video it appears he hasn't. Also once the heater core is out, what's the best way to check and see if it's clogged? Any help would be great.

 

Touch the heater core.....lines going in and out should be as hot has the rad hoses....anything else tells you the flow is reduced.

 

PS
Once it is out...
Just swap it....
Very good chance it will leak if reinstalled with the same prints/gaskets..making a big mess.
Some parts are so cheap....just replace it....and flush you cooling system first...I would hate to plug a new core....... Bet the cooling system has been neglected...remember you have a cast iron block....old coolant and iron = rust....it flakes off...and clogs stuff...thermostats, heater cores.... Then you loose the head gasket from corrosion.... And maybe the motor.

 

Thanks for the fast response. I will check the lines going in and out the heater core first and make sure there isn't a difference in temperature.

 

I'm assuming your coolant is full, and the system is bled. If not, check that. These cars can loose coolant from the thermostat gasket (among other places) at such a gradual rate, it evaporates off the hot transmission before ever hitting the ground. When coolant is lost, it's replaced by air, which rises to the highest point in the system - the heater matrix. Getting air in there will prevent heat from working before any signs of the car overheating. From the gradual nature of your problem, I'm inclined to suspect the matrix myself. But it would be great if the issue was a $20.00 thermostat, some G12, and an hour or two of your time.