Hello, the following problem, heating is not right despite new thermostat and new water pump. Engine temperature is between 92 and 95 degrees now have the presumption that the heat exchanger makes sluggish although both cooler hoses that go into the interior warm up. Funny is also that when I have the cover from the balance tank on and about 3000 & min. hold the heater warm and temperature goes down to 90 degrees has one of you still ne idea? thank you in advance