Hi im new to this forum , i hope some one can shed some light on my problem .

The car runs climate & its winter here at the moment anywaythe heater has been working fine then one day it only blows warm air the water temp is usal 90 degrees after around 5-10 miles driving
now ive been to the vw dealers and had the pc plugged in to check the heater flaps and motor settings allok and working.
Ive replaced the water pump with the later item with the brass impellor also the thurmostate , checked that it opened in a bowl ofvery hot water also repleced the header tank cap, took of the 2heater pipes behind the bulkhead and flushed it through with a hose and preasure washer there seems to be good flow with all the water very clean , also took a number of engine hoses of to see if there blocked all good , also can take the car on a long 10 mile 100 mph run and the air seems to get a bit warmer but not much ,ive got carboard covering the whole rad as well to try and get it to warm up quicker , one thing the bottom hose seems always cold/warm and the small header return pipe does not seem to return much water in the turms of flow the engine does not use any water no preasurization ect ect even with 19 psi ! please help the kids are blue buy the time they get to school .[&:][&:][&:][][]and im pulling my hair out what ive got left.