Expedition heater woes, warm then cool air

[mangus64]

Temp gauge sits in the middle, normal as far as I recall. Both dash/rear heat blow warm air but once out on the road both go cold, not just-started cold but cool. If you get on the throttle, blower airs gets warmer within seconds.
I've checked antifreeze level, full. Took off heater core lines and flushed hose-pressure water through them, seem to flow good.
I've read about the blower door breaking but that wouldnt affect both dash/rear heat I think.
Has all the symptoms of a stuck open thermostat except for the "normal" looking temp reading on the gauge. No matter, I'm buying one tonight and will replace. Any other ideas?
Also, radiator hose/heater hose never get hot enough that you cant hold your hand on them. Seems they should be too hot to hold for long.

Thanks
Mangus

 

[joedmti]

No heat too

After a Jiffy Lube radiator power flush, I lost the heat in the dash, but rear heat kept working fine. Lived w it for 2 years, but now no heat in rear either of my 99 XLT.
Swapped rear core, flushed the lines front and back, dropped in 2 thermostats, also checked and see that the blend door works.
Guage in dash looks right, but I have the same thing like you do w the hoses, they dont get hot enuff. Had radiator swapped out too. Coolant in reservoir is "too cool", never gets hot.....mechanic gave up, I'm looking for another mechanic..........

 

[mangus64]

Yeah changed t-stat this weekend, figured it was not it. It wasnt. Same result. Lukewarm heat out of both dash/rear heaters.

Someone mentioned a valve on the heater-coolant lines, does my 2000 Expy have this? If so where is it.

Any chance the A/C is running diluting my hot air with cold air?

Any help appreciated guys. It's cold up here today -5 in Montana!

 

[mangus64]

Flushed both cores today, all clean. I have hot coolant flowing through the cores so it must be something else. I see threads about the blend-door. Where is it and how does one get to it?
I didnt think it could be this cause both front/rear heats act the same but maybe they are broken.
Is there a thread somewhere on how to check the blend door?
Thanks
Mangus

 

[mangus64]

Ready to trade it off!

Alright folks, here's the latest status of my 2000 XLT Expedition heater problems. Sorry for all the posts but this is really torquing me off.

This morning it's a balmy -30 with wind chill. Expedition heat in both the front/back never gets above luke-warm in temperature. It'll make luke-warm heat at idle or if you leave the blower speed on LOW. Turn the blower speed up and it cools right off to cold air.

I flushed the cores yesterday, they seem to flow freely i.e. garden hose pressure water flows in/out at the same rate. Changed the t-stat over the weekend thinking the old one was stuck open, it wasnt.

Changing the temperature knob to cold to hot changes the air temp as expected. Gets real cold on cold, lukewarm on warm. Rear system behaves exactly the same so I dont think the infamous blend door(s) are the problem, but maybe I am wrong here.

I am thinking the only thing that makes sense at this point is that the return line to the block is plugged or restricted enough that coolant cant traverse the system at a rate to make good heat.

Is there a flow diagram of coolant that anyone can share? I think I have it figured out but would like to know for sure.

Any help GREATLY appreciated.

Mangus

 

[joedmti]

It was the water pump

Mang,

My 99 XLT (w 308K miles) was driving me and my mechanic crazy.
Top radiator hose and lower radiator hose were "warm", I had no heat from my dash or from the rear.
Dropped in 2 t-stats, flushed both cores, replaced rear core, no fix.

He pulls my water pump, and see's the impellers are worn off.
Impellers, you probably know what they are, and what their function is...I don't. They look like fins.

Bottomline is he drops in new water pump, FIXED!!!!!!

Mind you, there was nothing indicating that there was something wrong with the water pump.

 

[HFFH]

mang did you ever et it figured out

 

[mangus64]

Thanks guys for the info. Here's where she stands:

Yesterday I spliced in a piece of clear heater hose so I could visually see the coolant flow, per the the suggestion that the water pump might be bad. Nope, flows like a champ, good hot coolant screaming through the heater lines.

So, I figure it must be the blend door and I start taking the dash out for access. I got about an hour in and realized I was running out of daylight so I buttoned things back up. Didnt put all screws in, just made it so it was driveable.

While there, I listened for the blend door motion, sounds like it works fine i.e. I can hear it move and seal when moving to the cold/hot positions.

So in summary,
- I am confident I have hot coolant flowing well to the heater cores
- I am confident the blend door is working correctly

but perhaps it's broken and allowing cold air in to mix with the warm? Can anyone give me their thoughts on that scenario? That a piece of the door itself is broken and allowing cold air to leak and mix resulting in my lukewarm air temperature.

Rear heat behaves about the same although doesnt seem to get as warm as the front.

Other things I have noticed:
- upper hose never gets real pressurized, always can squeeze it to collapse even when hot. Taking coolant lid off releases some pressure but not much.
- inlet heater hoses are hot, outlets are cooler when blowers are running

At this point I think it has to be inside, something to do with the core or blend door, it's the only remaining item that makes sense. But other thoughts gladly accepted as it will be GREAT to get this fixed.

Also, one last thing I just thought of. Fix the rear heat system, by the looks of it, it is much easier to check the blend door on the rear system? See if it is broken first. If hot heat through the rear than the front blend door must be bad.
Does anyone have any good threads bookmarked on how to get to the front/rear blend doors the easiest?

Thanks for all the help
Mangus

 

[joedmti]

Still can be the pump

Mangus,

The impellers on the water pump can be worn off.
If the impellers are worn off the pump, you will not get any heat!

The pump can be pumping the water just fine, but if there are no impellers = no heat.

My symptom was that the top radiator hose and the lower radiator hose were warm and not hot. No heat in front of truck, no heat in rear.

Replaced pump, problem solved.

 

[joedmti]

Your on to it....

Mangus,

In one of your previous posts you said:

I am thinking the only thing that makes sense at this point is that the return line to the block is plugged or restricted enough that coolant cant traverse the system at a rate to make good heat.

Thats it! Its not traversing at the correct rate.
The impellers creates the suction to get it flowing.

Was the water pump changed in the past?

My pump was 11 years, with 308,000 miles of water pumping........