'02 4.6 No Heat

[mjonesjr84]

I've got an '02 Limited that the heat stopped working. The heat worked great all winter until we started using the AC. Today it was cool and when I tried to use the heat, it blew cold.

I have ran the EATC self check and returned no codes. That should eliminate the blend door actuator. There is antifreeze in the reservoir. The engine does not over heat and gets to proper temperature so I'd say the thermostat is working fine.

Anyone have any ideas?

 

[rocco123]

Is the heater valve opening? Manually move the actuator arm and see if both hoses get hot

 

[mjonesjr84]

Is the heater valve opening? Manually move the actuator arm and see if both hoses get hot

Which direction should the valve be in when there is a call for the heater? I know it doesn't seem to move no matter the EATC temp.

 

[rocco123]

I can say for sure, but if the eng is hot and you move it to opposite position with eng running and nlower on do both lines get hot and is there heat in the cabin?

 

[Harpua216]

is there intermittent heat while driving ie hot then warm, then maybe cool or hot again?

any syrupy smell behind the glove box? is it wet on the ground on the interior passenger side floor?

There is also the fresh air door that falls down and covers the blower box. very common, i just pulled mine out easily. you would still get heat with this but depending on outside temps, being there is a fresh air duct there, you may be being tricked into thinking there is no heat. any cold air behind the glove box?

I have had all these problems at different times and they fixed my heat/EATC problems....and more...

heater core or water pump starting to go? I have had these two problems.

 

[mjonesjr84]

No intermittent heat.

How do I check the fresh air door? Wouldn't removing it keep the max AC from functioning?

The floor is dry.

I haven't checked behind the glove box. What would that mean?

 

[rocco123]

If riding down the road u feel.a breeze in glove box the fresh air door could be broke. With glove box removed, you can see the door thru the screen. I had to wire mine closed.

 

[Harpua216]

No intermittent heat.

How do I check the fresh air door? Wouldn't removing it keep the max AC from functioning?

The floor is dry.

I haven't checked behind the glove box. What would that mean?

it actually makes the blower shoot amazing, clothes blowing AC at MAX. things is you are removing the door that stops recirc or fresh air from entering your system. there is a quick workaround and explanation but i think if you have NO heat you might want to look at your core or maybe some other lines or tsat or pump issues. your tstat could be stuck open? which would give you no overheat issue but maybe others.

anyway here is a like to the blend doors. behind the glovebox is the blower and on top a rectangle box with a plastic grate on the front, squeeze your hands in the grate and feel downwards if you feel something moving or some factory sponge that feels almost like a filter (but isnt its the door) - you havfe the problem/ but i dont think its your overal issue.

http://www.explorerforum.com/forums/showthread.php?t=284042&highlight=recirc+air+door+blower

 

[mjonesjr84]

The temp gauge comes up to normal range and I'm not getting any codes for low coolant temp. I'd think that would eliminate the thermostat and the water pump.

I'll have to check the glove box when I get home to see if there is air there.

I've held the vacuum valve in the heater hose in the opposite position for a bit and couldn't tell a difference in the air temp coming out of the vent with the temp set to 90*.

 

[rocco123]

Sounds like a fluid issue. If valve moved and no cabin air temp difference. How about temp of the hoses as you move the valve. If no temp difference it definately coolant problem. Either low level, blockage or pump just isn't moving the coolant.

 

[Harpua216]

my pump went with no codes. i had no heat and it was intermittent at the end. no low coolant is good it means potentially no leaks but as mentioned above there is some kind of blockage or somethings not doing its job.

 

[mjonesjr84]

I'm going to try the Degas bottle cap. I was able to take it off with the vehicle warm with hardly any pressure on the system.

From experience, a failing water pump will either leak out a weep hole or cause an over heating issue from lack of flow. The engine warms up to the normal temperature and stays there, even at idle and not moving.

There are no antifreeze leaks and the system is in the cold fill range.

I also noticed that the vacuum line coming off the valve on the heater hoses doesn't get any vacuum. Where does this go under the dash?

Like I said, the heat worked perfect until we started using the AC a couple weeks ago. Now when we tried to use the heat, it blows nothing but cold air.

 

[Harpua216]

I'm going to try the Degas bottle cap. I was able to take it off with the vehicle warm with hardly any pressure on the system.

From experience, a failing water pump will either leak out a weep hole or cause an over heating issue from lack of flow. The engine warms up to the normal temperature and stays there, even at idle and not moving.

There are no antifreeze leaks and the system is in the cold fill range.

I also noticed that the vacuum line coming off the valve on the heater hoses doesn't get any vacuum. Where does this go under the dash?

Like I said, the heat worked perfect until we started using the AC a couple weeks ago. Now when we tried to use the heat, it blows nothing but cold air.

might be your blend door, then. just a guess. but you hear it move? sometimes i hear mine sometimes i dont.

 

[mjonesjr84]

Yes I can hear it move. The EATC self check shows no codes too.

 

[mjonesjr84]

Is there a check valve where the heater line comes out of the head and 90* over to go to the vacuum operated valve? This is the one that comes out of the front of the intake on the passenger side of the alternator. The line is hot on the motor side of the black check valve, but not on the heater core side. It has an arrow pointing towards the heater core.

 

[rocco123]

It's a restrictor. Just replaced mine when I did my timing Chain and broke it. Got replacement at autozone. There is a peice in my old one I noticed that was no longer in there as I saw the new one had the restrictor peice inside. Maybe yours is busted

 

[mjonesjr84]

I took it out of mine just now.

I found the problem. It was the valve that is in the heater hose line that closes when the AC comes on. It was stuck closed and the valve broke.

Thanks for the help!

 

[rocco123]

Glad u found it.

 

[Harpua216]

nice! great job. I have to remember this one!

 

[rocco123]

I did bypass mine for for a week until I bought the part for $10. Just clamp on a small section of 1/2 inch copper pipe. Always good to have copper tube in your tool box in case a hose breaks.