I have noticed recently that the heater gets warm, but not hot at all, on my '97 Exp. 4.6L w/108k miles. I was suspecting one of two things:

1. Thermostat stuck open

2. Fouled heater core

Yesterday, I replaced the thermostat. Long story short, the old thermostat was not stuck open & the heater still functions the same as before(warm, not hot).

Does this sound like a heater core issue? Can someone step me through the process of flushing the heater core? The top radiator hose notwhithstanding, I don't know which hose is which under the hood.

Thanks in advance.

 

Anybody?????

 

When the truck is warmed up are both radiator hoses hot? I would suspect that you may have a blend door that is allowing cold air to mix with the hot air. Are you able to adjust your temp so that it blows cold or does it stay the same lukewarm temp?

 

The radiator hoses are both hot. Also, I am able to adjust the temp so it blows cold. Everything seems to operate normally, except the heater only gets WARM, never HOT.

I'll put it this way; If you had been driving for a while, you wouldn't want it any hotter than it blows now, but it used to get so HOT, it would run you out!

If it's a blend door issue, would the blend door fix at the top of this forum work for me?

Thanks in advance!

 

Your heater core is ok. Your blend door may be ok but for whatever reason it sounds like it is not closing all the way.

Anyone else encounter this problem?

 

how is the temp on the hoses running to the heater core?

 

The heater hoses are hot.

 

is the air volume thru heater really good? Wondering if the electric motor is slowing down and not getting enough air thru. Also check to see if there is anything blocking the airflow into the heater core. If both temps on the hoses are hot then you are not transferring the heat from the water hoses to the air temp. in the core. Also your core might have something bad like fins. just like the radiator has. I have seen in dusty conditions that the fins have been covered over with a coating of dust, etc.

 

The air flow through the vents is normal. I'm going to flush the radiator & heater core. If the situation does not improve, I'll probably have to ake it to my mechanic & let him look at it.