Heat isn't blowing hot on high. I checked for air in line by squeezing the upper hose which is soft. Tstat was changed. Heater valve was changed. Upper hose gets hot after squeezing it and heat feels ok for a little while. Could a faulty hose do this?
My car has 16500 miles.
My car has an automatic transmission.
A faulty hose can not create this symptom. If a radiator hose can be squeezed, it only means there isn’t pressure in the cooling system, but this can indicate a problem. Cooling systems are designed to hold pressure. This raises the boiling point of the coolant so it can run above 212 degrees Fahrenheit. These signs suggest that maybe the thermostat is stuck open. A stuck open thermostat will allow the engine to cool to much once you drive for a short distance. Of course, pressure in the cooling system fluctuates for many reasons and you may be just squeezing the hose at a time when there isn’t any pressure. The best method to check the actual temperature of a motor is the use of an infrared thermometer. You can find one from you local auto parts store for not too much. A little steep, but the absolute best method to know what temperature your motor is running at.
If the temperature is correct, I would suspect you may have a clogged heater core. What does your cooling system look like? Is is very dirty or muddy looking? If so, a clogged heater core is very likely. You can check this by feeling the two heater hoses entering and exiting the heater core. They should both be warm or hot. The one that enters will be hotter than the one that exits. What’s important is one that is not cold. If you determine the heater core is plugged, there are methods to attempt and unplug it. I would do that two or three times before I decided to replace it. Assuming your attempts to unclog the core fail.
Air in the system can do this as well and air in the system can cause other problems too. Fill the cooling system through the radiator when the cooling system is cold before your first start of the day. Then top off the overflow container. The overflow jug is likely part of the pressurized cooling system. While your at it, make sure the radiator cap is good.
If all else is working properly, this about covers it. Other than an extremely dirty cooling system can cause restriction throughout the cooling system that can create this problem and more. A qualified professional from YourMechanic can come to your car’s location to diagnose the heater issue so that this gets properly repaired.