Heater matrix air lock possibility

[Tom leeming]

Hi guys

I need some help, i believe I have a heater matrix air block, when i start the car i can hear a surge of water being pumped behind the dashboard and towards the glove.compartment and every couple of weeks I have to top up coolant with a little dribble as it goes below the min line in the tank. I have tried running the car upto temperature with the cap of the tank and squeezing the hoses.to try and push the air out. My car.doesnt overheat and runs fine. Always stays at 90 degrees. All the pipes get hot while running so I believe I've got good flow. What is the best way to get rid of the noise behind the dash??

 

[NHN]

I'd drop the coolant via lowest point, usually the rad bottom outlet, then replenish, usually I would just veey slowly refill & leave it standing over night with reservoir cap of, swapped a few before & been fine.

 

[Tom leeming]

I am a novice at doing this, is it a common mistake for a mechanic to make as I had the reservoir tank replaced recently as it was old and grubby. Once refilled would you need to run the engine and fill it up as the water pump pulls water through???