[lanep]

I changed the water pump and thermostat and now the heater in the car does not heat up. It will heat up at idle but once it reaches to 50-55 mph the temp. starts to go down and the heat stops working. I have changed the thermostat 2 or 3 times now and the problem is not fixed. I have also put card board in the car as well to block the wind, this has not helped either. Any suggestions would be very helpful!
Thank you!