We recently purchased a 1997 Mazda MPV sport with 140,000km to replace our other 97 MPV which had over 350,000km on it. Problem is we can't get any heat out of the heater core, have had it flushed, tried the parallel pinch routine, nothing. Is there something else that could be wrong or should I just try removing the heater core and putting in another one, I have already replaced the rad and it was quite fouled. Also the fuel gauge is not working, new sensing unit?