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Heater not working

Tiny
MOO2CAR
  • MEMBER
  • 2002 LINCOLN NAVIGATOR
  • 5.4L
  • V8
  • 2WD
  • AUTOMATIC
  • 170,000 MILES
My vehicle listed above is not providing any heat in the car. A couple days ago, I decided to check to see if I can eliminate some of the possible causes of no heat that I have read about and watched on the internet.

1. I first checked the coolant level in the reservoir and it was adequate, slightly above the minimum fill level.

2. I started to idle the car. The outside temperature was 70F. A few minutes after starting by idling the car, I touched the upper hose to the radiator, and it was cool to the touch. This indicated to me that the thermostat was working and coolant flow to the radiator had not started.

3. After a while, the thermostat opened, coolant flowed into the radiator and the upper radiator hose became warm to the touch.

4. After a while, I used an infrared thermometer to measure the temperature of the various hoses, The top radiator hose was 150F, The bottom radiator hoses with its many branches averaged about 130F. The coolant temperature was 183F.

5. There were two heater hoses going into the firewall, one upper and one lower. Each of them is T-eed so that in total, you have 4 hoses going into the firewall. The Navigator has a rear heater, so I am guessing that the split at the T is to let one branch be for the front heater and the other for the rear heater. If this is not correct, please let me know.

6. All the hoses felt warm to the touch. I used the infrared thermometer to measure the temperatures. For the top heater hose, the temperature for the line between the engine and the junction at the T was 126F, straight on the other side of the junction, it was 115F and on the T side (presumably the hose that goes to the rear), it was 120F.

7. For the bottom heater hose, the temperature for the line between the engine and the junction at the T was 116F, straight on the other side of the junction, it was 115F and on the T side (presumably the hose that goes to the rear), it was 134F.

8. In the meantime, I had set the desired temperature in the cabin at 90F and the climate control was set on automatic. With the outside temperature 70F, I expected the car to heat. I put an oven thermometer in the driver's side floor vent, left it for a while and the temperature was 60F. It felt quite cold as if the AC was blowing directly on my foot.

9. If instead of selecting automatic, I choose the Floor/Pnl button, the the air coming out of Floor vent is 70F while air coming out of the panel vent on the Driver's side is 57F

10. The air coming out of the rear floor vent and the rear roof vent felt more warm than the front heater. The temperature out of the rear floor vent and the rear roof vent was 91F each.

11. What could be the cause of my not having heat?

12. Pictures below show the heater hoses in the hood as well as the temperatures described in paragraphs 6 and 7.
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Tuesday, March 23rd, 2021 AT 12:42 AM

12 Replies

Tiny
STEVE W.
  • MECHANIC
  • 13,443 POSTS
This sounds like you have low engine coolant or the temperature blend door actuator stopped working but to but sure this video and guide can help us fix it.

https://youtu.be/SNRb6pSwYuU

and if the temperature blend door needs replacement here is a guide that can help with diagrams below to show you on your car.

https://www.2carpros.com/articles/replace-blend-door-motor

This guide can help as well

https://www.2carpros.com/articles/car-heater-not-working

Check out the diagrams (Below). Let us know what happens and please upload pictures or videos of the problem.
You are correct about the T's feeding the front and rear heater cores. From your description and measurements it sounds like a partially plugged heater core is the problem. Being this is an older design core I would likely try back flushing the core to see if you can restore the flow through it without replacing the core as that is not a fun job. Replacement requires the dash be removed, then the heater case and finally the core. To do a flush you would start by partially draining the cooling system OR you could use some pinch off clamps to clamp off the heater hoses, for that you will want 4 clamps, you need to clamp the hoses on the engine side of the T as well as on the hoses that lead to the rear heater. That way you isolate the front heater core. Now you can remove one of the heater hoses and catch the amount of coolant that will come out. Next disconnect the other hose. Now you will connect a flush gun or a garden hose to the heater core connection and flush water through it in both directions. For this the flush gun works better as it will agitate the water flow and break up anything it can during the flushing. Once you have flushed the core a few times you reconnect the heater hoses, remove the clamps and test the system. The amount of water added this way is minimal and just adding fresh coolant to top up the system will resolve that.
Now you can test the system and see if the heat has improved.

As you say that one side seems to get warmer than the other I would also verify that the temperature blend doors are working. To do that you simply set the temperature lower and see if the air temperature follows. So if you can control the temperature up/down the actuators are working. If one or more fails there would be no temperature change in the air regardless if you selected heat or A/C.
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Tuesday, March 23rd, 2021 AT 3:18 AM
Tiny
MOO2CAR
  • MEMBER
  • 55 POSTS
Thank you Steve for your reply. I have a couple of other questions.

1. A friend told me that from the temperatures and the feel by my hand, the inlet and outlet heater hoses are both warm, so he thinks that the problem is not with the heater cores but more likely with the blend doors. What do you think?

2. Can you give me some advice on how to remove the metal crimps surrounding the hoses near the T so I can connect the hose to flush the system? Or do I have to cut the heater hoses? In the Navigator, I cannot directly see the connections at the firewall and it will be very difficult for me to connect the flush kit there.

3. Does the rear heater have its own blend door?

4. None of the service manuals I have - Ford's and Chilton's - has a plumbing diagram for the Lincoln's cooling system. Do you know any that has?

Thank you.
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Tuesday, March 23rd, 2021 AT 2:28 PM
Tiny
STEVE W.
  • MECHANIC
  • 13,443 POSTS
The problem with the temperatures being a valid test is that the T connectors make it suspect. On a single core the heat goes in and stops, with the two cores the heat makes it through the rear core and then causes the water on both sides to have the same temperature. If the front core was flowing properly you would have one hose hotter and the other one colder on both cores. You show both of the hoses for the front core at the same temp which shows no flow.
The crimps cannot be removed without damaging the hoses. You would need to remove the lines from the core or the engine side to gain access.
Rear heater has it's own controls for hot/cold and that includes a blend door.
No real diagram of the hoses other than what is attached, the front ones T off and go under the truck to the rear unit. The same applies to the refrigerant lines.
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Tuesday, March 23rd, 2021 AT 4:18 PM
Tiny
MOO2CAR
  • MEMBER
  • 55 POSTS
Thank you very much Steve. A couple more questions:

1. As I mentioned, before, when I had my climate control on Automatic, and I put my hand near the floor vents, the air blowing out of the vents there felt very cold as if the A/C was working. Does the A/C always run? Even when I had the set point 20 degrees higher than the outside temperature?

2. If I take it to a reputable shop to do the heater core flushes, would they normally do the forward and back flushes by connecting to the hoses at the firewall?

I appreciate all your help.

3. Can you include the names of the various parts shown in the diagram that you posted? Thanks.
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Tuesday, March 23rd, 2021 AT 6:32 PM
Tiny
MOO2CAR
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Can you include the names of the various parts shown in the diagram? Thanks.
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Tuesday, March 23rd, 2021 AT 6:33 PM
Tiny
STEVE W.
  • MECHANIC
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It depends on the vehicle but most with automatic controls run both AC and heat to dry out the air coming into the vehicle depending on the exterior temperature and humidity. Hmm, the list was supposed to be attached. Here it is:

A good shop will not take your or my word as to the problem, they will diagnose it and then tell you what they found and what they recommend as it's there name on the line. But I would suspect they will go through the same steps and if they decide to flush the core they will disconnect the lines and probably power flush it the same way I suggested. Then see if things improved.
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Tuesday, March 23rd, 2021 AT 7:47 PM
Tiny
MOO2CAR
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  • 55 POSTS
Thank you very much. I will report back after I take it to the shop.
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Tuesday, March 23rd, 2021 AT 10:16 PM
Tiny
STEVE W.
  • MECHANIC
  • 13,443 POSTS
Okay, we'll be here. I hope they get it all straightened out very fast.
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Wednesday, March 24th, 2021 AT 5:49 AM
Tiny
MOO2CAR
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Sorry, it has been a while. I took it to a shop that promised to flush both heater cores for me. However, on taking it, they reported back to me that the radiator is leaking on two sides and that I need a new one. This is a cost that I am not sure I want to incur on this vehicle. I just had it replaced in 2017. I'm going to seek the opinion of the shop where I had it replaced.
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Thursday, April 8th, 2021 AT 4:54 PM
Tiny
STEVE W.
  • MECHANIC
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I would have the other shop look at it, depending on the unit some have lifetime warranties.
As for flushing the cores, did they try at least or complete that? Or was it a, well you need a radiator so we're not touching it until you pay for that?
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Thursday, April 8th, 2021 AT 5:04 PM
Tiny
MOO2CAR
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Yes, he said he was not going to flush because it will damage the radiator more and they won't do the flushing unless I get a new radiator. I will take it to the shop I bought the current radiator from as soon as I get the time to take it there. In the meantime, I am watching the coolant reservoir to see if there is any significant drop in level.
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Thursday, April 8th, 2021 AT 5:55 PM
Tiny
STEVE W.
  • MECHANIC
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You should be able to see any leakage on the sides if you use a mirror or look inside the fan shroud area. It sounds like they saw a way to make money, I hope I'm wrong. Plus if they do the flush of the cores the proper way, they wouldn't even touch the radiator. Sounds like they wanted to do a coolant flush, that will do nothing for the heater cores as it doesn't agitate the coolant going through them. This is the type of flush you need.

Eric is a top notch tech who acts like a goof at times but he knows his stuff.

https://www.youtube.com/watch?v=LtnVyFNyU1w
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Thursday, April 8th, 2021 AT 7:08 PM

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