The heaters of my Mitsubishi van aren't working properly by blowing only cold air.
After doing my research online I found some posts talking about the thermostat and coolant (air blocks).
The first time I added coolant to the reserevoir, it was completely empty and I had the motor run for 15 minutes. After driving with it for some weeks there was no difference when turning on the heater.
Today I added more coolant and tried to get an air block out if that would be present. After opening the radiator it was completely full. I put on a funnel to prevent overflow, started the car and waited for 30 minutes. The coolant raised about 4 cms into the funnel and there were no bubbles coming out of the radiator. The air blowing was still cold, no success.
Any suggestion for a non experience car person to check before going to a mechanic to get it fixed?
Added image for a visual guide in case it helps! (filled up the reservoir near the battery and used the funnel where the big silver cap now sits)
Thanks in advance for any suggestions!