No heat on idle

[zfortna]

Just got a used 06 XLT. Noticed a radiator leak a day or two after I brought it home so back to the shop it went and the radiator was replaced and the cooling system was bled. This seemed to fix a majority of the issues, but the heater still blows cold air when the explorer is idling just like it did before the radiator was replaced. As soon as you get on the gas (and even if you tap the gas in park), you immediately get hot air again. What gives?

 

[midiout]

Most likely the coolant is low again. As you rev the engine, the coolant moves thru the system, but at idle the water pump does not move much collant. Does the car smell like coolant inside ? That would be my guess, unless there is a head gasket problem, but it would have to be a big one for that much coolant to lost after the radiator change and flush.

 

[zfortna]

I'll check the coolant level again at lunch and see how it looks. I assume my best bet would be to check it with the engine warm and idling since that is when the problem occurs? There is no coolant smell in the car when it is blowing cold air. Could the cooling system need to be "burped" after the flush as from what I understand the heater coil is the highest point in the system so that is where the air would collect?

 

[Carguy3J]

You might also want to check the heater control valve. It is vacum operated. Also check for any leaks/loose connection on the vacum line leading to it.

 

[zfortna]

Where would I go about looking for the heater control valve and the vacuum lines. Just got the explorer so I'm not familiar with where everything is yet.

 

[Carguy3J]

Where would I go about looking for the heater control valve and the vacuum lines. Just got the explorer so I'm not familiar with where everything is yet.

Follow the heater hoses from connection on the firewall, towards the motor. You can't miss it; it's a big black plastic valve with multiple heater hoses connected to it.

Use the forum search feature, search heater control valve, and I;m sure you'll find pictures and more info.

I would also recommend picking up BOTH a Chilton and Haynes manual for your vehicle. If you plan on do alot of your own work, it might also be a good idea to get a subscription to www.alldatadiy.com It's the same repair info that professional shops use.

 

[zfortna]

I went home at lunch and check things out. The overflow was full, but when i removed the radiator cap, it wasn't even close to full. I filled it up, started the engine and it was still blowing cold air. I checked it again after the engine was off and it was still full. Let it sit for about 15 minutes while I was doing something else, came back out, fired it up and it was blowing hot air at idle. Will test it again tonight when i get home when the engine is completely cooled and see what happens.

 

[rodywl]

same is happenning to me in my 94 I have no idea what it is yet

 

[zfortna]

Well after I got hom last night, it was back to blowing cold air. It appears it blows warm air when idling at 1000RPM, but not at 500RPM. Back to the shop it went as it was still under the 30 day warranty and they are replacing the thermostat now as they said it was stuck. I guess I'll find out tonight if that resolved the issue.

 

[zfortna]

New Thermostat and housing. Same problem.... Anyone have any other ideas?

 

[rodywl]

I changed my heater core and my problem solved you could try there was something stuck in mine that didnt let the coolant flow on low pressure only when I used to rev it!...

 

[mattt9998]

Zfortna... did you ever figure this out? I am having the same issue.

 

[zfortna]

Zfortna... did you ever figure this out? I am having the same issue.

Yeah, but you arent gonna like it. They ended up looking inside the engine block, and found melted plastic, and ended up replacing the engine.....the explorer was never the same after they did that and we have since gotten rid of it.

 

[mattt9998]

Outch. Thanks for the response.