Hello ALL!

I'm a new member. Just bought a 1999 Ford Expedition EB edition about 2 months ago, and I have to say, me and my pregnant wife love driving it and very happy with our choice. 3 weeks later, we had a leak on the rear coolant hoses. I brought it back to the dealership where we got the truck from and they fixed it. They cut 2 of the 3 coolant hoses that can be seen on the rear passenger side and patched them with rubber hoses. Now the winter season is about to start and I just noticed that the heater is not working on both front and rear. I've been observing this for a while and and no matter how long we drive it, play with the temp dial (set to 29 or max 32), the air coming out of the vents never gets hot. The AC is fine and cool but the heat is lukewarm and never hot.

1. Front Heater. I've done my research here and elsewhere and based on the info I've seen online, I can only assume that It could be the heater core or blend door problem for the front. But before I start the tedious "Dashboard/Console Removal by Alan T" is there a way to determine/verify that it is indeed the heater core or blend door that's causing the problem before removing the dashboard? For instance, how do I know that it's not the thermostat? I heard the blend door makes a flapping noise when it's broken? Any additional info. or areas I can check to isolate the problem would be helpful.

2. Rear(2nd & 3rd row) Heater. I haven't had any luck with the rear heater. Are there any valve(s) for the rear heater that might have been dialed down or closed when the dealer fixed the hose problem? Where is the rear heater core or system located? Like the front heater problem, is there something I can check to determine the cause.

I'd appreciate any help, instructions, or steps you can provide to pin point the problem(s).


Thanks for all the help.

 

Before attempting the blend door repair I would first verify that you are getting up to proper temperature. Second I would make sure that you're getting proper coolant flow through both heater cores.

 

The dealership that did the repair, is that a Ford dealer, or something else? I'm just asking because if it was not a Ford dealer, I would suspect they fixed your leak by bypassing the heater cores all together. The input lines for the front heater core can be seen pretty easily if you get in the right position. They come out of the rear firewall just to the passenger side of center and very high in the engine compartment. You have to squat down a bit in front of the vehicle to be able to see them. The rear core connections are on the passenger side of the engine, just in front of the a/c accumulator, between the fender and engine exhaust manifold. They run down under the cab and to the back of the vehicle's core, parallel to the rear a/c lines. If both of those are still connected, with the vehicle warm and running, feel the metal lines going to the rear core. They should both be pretty warm. The easiest place to get to them is under the passenger side of the vehicle about even with the front door. There are 4 metal lines there. The heater lines are inboard. The a/c lines are two different sizes and one is insulated (originally). The heater lines are both the same size all the way back.

If they are both hot, you've got good flow.
If only one is hot, you might have a blockage in your cores
If neither are hot, you might have a thermostat that is stuck open (that really doesn't seem likely to me. I think they usually fail stuck closed) or a problem I'm not familiar with.

It sounds like you have the automatic enviro controls. Maybe it has a problem with the temp sensor. I really don't know how to test that. There is probably a way to manually drive the blend doors all the way to the hot position. That would tell you a lot. But I don't know how. Sorry.

With both front and rear misbehaving, it is hard to believe you have a blend door problem. They would both have to be bad. Just from what you've said, I'm betting on the heater hoses bypassing the cores altogether. But maybe I'm a little biased because that's what just happened to me! If that is it, it's an easy fix as long as your core is not leaking internally.

I hope someone else will come along with some more troubleshooting techniques for the parts I'm not familiar with. Also, mine is a '97, but I think most of the enviromentals are the same.
Good luck.

 

Just a couple FYIs here:

T-stats can fail open or closed, there is no set pattern. When they fail closed people notice it right away because the engine will overheat. When they fail open, most do not notice the slower warm-up time or that the engine might be running 20-30 degrees cooler. So t-stats stuck open tend to go longer before they're diagnosed.

With the front and rear thing, often the rear fails and the driver will not notice it for the longest time. It's usually when the front fails (like in this case) that the driver starts poking around and finds the back isn't working either. So although it might seem like both went out at the same time, they in fact might not have.

 

Thank you.

1. How do I verify the temperature? Do you mean check the thermostat?

2. Checking the heater cores? I know where the front heater core is, where is the rear? I will also check the lines if they are hot/cold.

 

Thank you!

It wasn't a Ford dealership. As for bypassing both heater cores, I will check the lines. Where do you find the heater core for the rear? Also, I only saw 3 lines when I crawled under (rear right passenger side) when I had the leak. There were 2 insulated if my memory serves me right. And at that time, the leak coming out of the lines were hot. But, I will check again. Its hard to do that right now since it's been raining and suppose to rain until Sunday.

As for the heater core leaking internally, I haven't seen any staining in floor carpets, neither front or back.

Yes, it has an automatic temp control which we barely use anyways.

 

I will be checking the thermostat tonight. I'm hoping this is the problem. I ran the truck for about 15-20mins yesterday and i noticed the air is a bit warmer than the usual when I set the temp to 32C. But I'm still not getting the proper air temp. that's for sure.

 

1. Aiming one of those laser thermometers at the t-stat housing is the best way.

2. With the engine up to full temperature and running, grab ahold of the heater hoses near the firewall. Both should be too hot to hold and they should be pretty much the same temperature. If there is a significant difference in the temperature between the two, then the heater core needs to be flushed or replaced.

 

Okay, I will check it out. I will look around for those laser thermometers and purchase one.

Just another quick one, I already know where the blend door, heater core & actuator are located for the front, but where do I find the rear heater core & blend door? Are both front/rear being controlled by the ones at the front under the dashboard? Or each has it's own separate heating/cooling system and located in 2 different areas?

Thanks.

 

Also, check the vacuum controlled heater flow valve.
It shuts off coolant flow thru the heater cores when the A/C is on.

 

I've heard about this from several different heater posts, but my '97 manual makes no mention of this solenoid. Is it something on the newer years? I sure haven't seen it either, and I just had the entire external hose system removed.

 

I'm fairly certain that valve don't exist on a 99 Expedition.

 

I was looking for this pressure valve as well, and I don't think it exists on 1999 Expedition.

Okay, so I finally had the chance to check out the hoses. I took the car for a ride for about an hour or so, then went back home check the hoses and both Front & Rear are hot. I also took some pictures. Please see link. I'm starting to think it's the blend door. Played around with the temp. control some more. I started it at 15C then slowly moving the temp up to 32C. I didn't hear any clicking or moving parts but I certainly felt the difference as I press the temp (red) button and increase the temp. Still, the air coming out of the front and rear vents are not hot enough.







My next move is to check the Tstat and then flushed the coolant again. Could it be that there is air in the system?

Also, I noticed that there is a hole in the firewall that is not plugged. Do you guys know what goes in here?

 

If the hoses are the same temp (hot) then you've got good flow through you cores. Next thing to check is your tstat. My truck has a 190 deg tstat in it. You should have close to that temp on the tstat housing. The ir thermostat like harbor freight sells is a good tool to measure it. If you verify your tstat is working, I think you should check your blend doors. The rear core is accessed thru a compartment at the rear of the vehicle on the drivers side. It's a door just like the one that hides the jack on the pass side. Pull it off and you can see the whole unit.

I'll look up what actuates those doors, front and rear and let you know how to test, unless someone beats me to it. I'm guessing when I say the front is vacuum powered and rear is electric.

 

Also, don't think flushing or air is a problem. If both hoses are hot, you've got good flow.

And I have the same hole in mine. It just has a plastic plug in it. Not sure why. Some option or for future expansion.