Lukewarm Heater

KMREBER

MEMBER
FORD ESCORT

Ford Escort, 1998, 130,000 miles, 4 cylinder engine. My heater is is blowing lukewarm air. Before this started happening, the needle on the temperature gauge would always reach right in the middle of the C and H after being fully warmed up, and the heat would be very warm. Now, after idling for some time, the needle will reach nearly the middle and the heat will blow fairly hot - but as soon as I start driving, the needle drops down to or below the C and the air blows luke warm to cold. Per Ford dealer, I've had the thermostat replaced twice. Also, the mass air flow has been replaced, my water pump is new, my radiator is new, and I don't have a coolant leak. Would this be a heater core problem?

1 Reply

MIKE H R

MECHANIC
3,094 POSTS

It sounds like there is still a problem with the thermastat. What the thermastat does is limit the circulation of water enabling the water to heat up. When you drive the water is cooled by the air going through the radiator. It sounds like the thermastat
is not working right. There are a couple of diferent thermstats that are available the most common are a 160 and 180 degree. The lower number lets the engine water heat up to 160 degrees before opening. The 180 does not open until the water reaches 180 giving more heat. To check, try taking off the radiator cap while the engine is cold. Take some water out. Start the car and let it run. You can tell when the thermastat opens. 1. You can see the water circulate inside the radiator 2. Feeling the hoses at times, when the thermstat opens the return line will get warm. When it opens check the guage and see what it reads. After replace the radiator cap and drive the vehicle if the temperature drops to low the thermastat might be stuck open not letting the engine to heat the water properly.