Good day. Am wondering what the best way to clear out the Heater ( in case that's the issue ). Would it be to take the two hoses off the engine side of the firewall and shoot water in one of them with a garden hose?

Engine heat gage generally goes to half way and stays there. But, no heat just cold air. If idled after warm the temp. will slowly climb way up, still no heat. Lots of cold air blown out.

 

you could try reverse flushing it that way, I have had limited success.
you do not say what type of vehicle it is, if it is a d2 there is no heater control valve so hot water should always be flowing threw the heater core, unless your out of coolant
ps. Also that gauge will always sit in the middle, until it'd to later.

 

Thanks. It's a D1, '95 Model.

No water leak on the floor or any indication of anything else happening.

Is there anything else that would cause it I wonder, e.g.: needs new core? It takes a long time to heat up to where the gage is showing 1/2
way up. ( Problem in Cold weather Canada, but I assume it because 300TDI is 2.5ltrs replacing 3.9ltr engine. )