Heater question

[digifoss]

Ever since I bought my Explorer, when I warm it up on cold mornings, the heater will blow cold air until the vehicle starts moving no matter how warm the engine gets. Once it starts blowing warm it heats the car quickly, but if I stop and let it idle too long, the air from the heater slowly get less and less warm, it never goes completely cold again but it does cool off until I start moving again.

 

[94Eddie]

Does it do the same when using the AC? Can you still select what vents the air blows from? Do you have the automatic climate control option?

 

[digifoss]

The A/C works normally, only the heater is affected. I can select what vents blow air no problem, I have regular a/c , front and rear controls.

 

[Rcflyer330]

I am thinking it might be one of a few different issues. My first idea is the heater core is plugged and needs more flow from the engine water pump to push through it. On that same thinking the water pump may be going bad. May also be the heater control valve or could be air in the system. Oh and a big one stuck open thermostat.

How well does the rear heat work?
Have you checked the coolant level in the radiator not the overflow tank?

So a few things you can check is coolant level in the radiator and if you have a scan tool look at live data for engine coolant temp as it warms up. A stuck open thermostat will eventually throw a code but that can take some time. It should not take any more than 8 minutes driving from full cold to get to full temp even at very low temps. This should be around 3 to 5 miles.

 

[94Eddie]

I would say the basis of your problem is not getting enough coolant to flow through the heater core. It seems to work fine when the engine is at higher RPMs which is when coolant is flowing at higher volumes through the system. This could be due to the items Rcflyer330 stated. Heater core restriction, failing water pump, bad thermostat, low coolant or air in the cooling system.

 

[digifoss]

I am thinking it might be one of a few different issues. My first idea is the heater core is plugged and needs more flow from the engine water pump to push through it. On that same thinking the water pump may be going bad. May also be the heater control valve or could be air in the system. Oh and a big one stuck open thermostat.

How well does the rear heat work?
Have you checked the coolant level in the radiator not the overflow tank?

So a few things you can check is coolant level in the radiator and if you have a scan tool look at live data for engine coolant temp as it warms up. A stuck open thermostat will eventually throw a code but that can take some time. It should not take any more than 8 minutes driving from full cold to get to full temp even at very low temps. This should be around 3 to 5 miles.

I can rule out everything except the heater control valve, which I have suspected all along but don't know where it is located. I assume it's a valve that opens to let coolant circulate through the heater core ? I have had this happen on previous vehicles and assume the Explorer has a similar valve somewhere. Where would I start looking for this ?

 

[2010 Eddie Bauer]

I can rule out everything except the heater control valve, which I have suspected all along but don't know where it is located. I assume it's a valve that opens to let coolant circulate through the heater core ? I have had this happen on previous vehicle and assume the Explorer has a similar valve somewhere. Where would I start looking for this ?

How have you ruled out the heater core? I was getting poor heat (100 degree heat coming out of the vents) and I flushed my cooling system. I bought several of the Prestone flush chemicals and ran them through the cooling system for a few days with the heater on full blast the entire time so it would circulate throughout the heater core. After I drained the coolant, I filled it with another "flush chemical" and distilled water and drove it for an hour with the heat on full blast. Once I did that, drained the water, and refilled it with the proper coolant I am now measuring 155 degree heat with a thermometer coming from the center vent on full blast. The heat dying down when you idle is a tell tale sign of a heater core restriction. The temperature will always drop a little when you idle, but it should not be noticeable.

 

[Rcflyer330]

I can rule out everything except the heater control valve, which I have suspected all along but don't know where it is located. I assume it's a valve that opens to let coolant circulate through the heater core ? I have had this happen on previous vehicles and assume the Explorer has a similar valve somewhere. Where would I start looking for this ?

It's in the engine bay in a heater line going to the heater core. Its is vacuum controlled i believe. Never heard of one failing though the other options are much more likely.

 

[digifoss]

How have you ruled out the heater core? I was getting poor heat (100 degree heat coming out of the vents) and I flushed my cooling system. I bought several of the Prestone flush chemicals and ran them through the cooling system for a few days with the heater on full blast the entire time so it would circulate throughout the heater core. After I drained the coolant, I filled it with another "flush chemical" and distilled water and drove it for an hour with the heat on full blast. Once I did that, drained the water, and refilled it with the proper coolant I am now measuring 155 degree heat with a thermometer coming from the center vent on full blast. The heat dying down when you idle is a tell tale sign of a heater core restriction. The temperature will always drop a little when you idle, but it should not be noticeable.

Well, I may be a little hasty in ruling the heater core out. My coolant system is very clean, overfill tank, coolant, hoses all very clean. PO was a maintenance perfectionist, always changing fluids and filters, flushing coolant system, etc... way before its necessary. I suppose it is possible but I will still check the valve first.

 

[Mbrooks420]

The valve will be easy to find, it’ll have to be inline with the heater hose.