I have noticed over the last 2 months that my heater is not anywhere near as hot as it use to be. I can also hear bubbles gurgling in the heater.

I have just drained cooling system, filled with new coolant, bled the system via the bleed screw on the top hose BUT still I hear this bubbling in the heater and still not very hot - only warm.

The only thought I have is that the water pump is on its way out and not pumping water system enough. Being cold weather not noticeable change in temp gauge reading.

Any thoughts please.