2010 Ford Explorer overheating when accelerating, no heat in cabin

My 2010 Ford Explorer experienced a radiator leak between the radiator and the plastic tank on the top, so I replaced that, we were still not experiencing any heat while driving it. I watched a couple of videos on how to “burp” the system, to no avail.

Next I replaced the thermostat, and “burped” it again, still no heat, so I drained and flushed the system yet again and still no heat. What else is there to check? I have the Haynes manual and did the flush and fill the way the book said and still have no heat I am about to lose my mind.

The blend doors sound like they are opening. They are not clicking like they are broken.

The heater is on full the entire time, I have not rotated the dial since I started this.

I unplugged one of the hoses on the heater core and blew into it, the hose was bone dry and I blew into the end of the hose and fluid came out of the cabin side metal tube. I also plugged a water hose into the tube and ran water through it to make sure it wasn’t clogged, it is not. Front and rear heater cores.

Here is everything thing I have done from the start:
Replaced Radiator.
Replaced Thermostat.
Drain and flush and re-service.
Checked for leaks out of the water pump weep hole (none) and operation of pump, the upper hose gets hot and I feel water go through it when the thermostat opens.
Check the radiator cap for pressure, it opens at 20psi and hold between 17-19psi. Replaced radiator cap anyway.
Removed supply hose and ran coolant to help purge trapped air.
Ran water through the supply and return hoses on the heater core. On the front and rear.
Check operation of heater control valve, works.
Turned vehicle on while watching the exhaust pipe, a small amount of water on initial start up in the morning but no smoke.

Problems still occurring:
Drive vehicle it over heats but returns to normal at idle I also get the coolant light that extinguishes when the car returns to idle. Even though it says its overheating the car has not pushed coolant into the expansion tank.
The car will not take any more coolant, and only overheats after the fan comes on. And still no heat.

My background is no car experience, I am a helicopter mechanic and if this was an AH64 I would be done by now. SO please take it easy on a rookie shade tree mechanic.

Should add, 4.0L engine, no oil in water after flush and the engine oil looks like engine oil not milky. Next step was a water pump someone please talk me out of that.

Get the engine up to operating temperature.

With the engine idling, loosen the upper radiator hose clamp.

Take a small flat bladed screwdriver or something similar and insert in between the upper radiator hose and the hose neck. Allow the engine to continue to idle until all the air is purged from the cooling and constant heat comes out the vents.


Could there be that much air left in the system? My expansion tank is full of fluid and so is the top of the radiator


I just replaced the water pump on a 97 accord. And even though the radiator/reservoir were full, there was air trapped in the system where the was little/no heat, and the temp gauge would start climbing.

Purging the system of air thru the upper radiator hose got the heat working and temp gauge is now steady.



Going to try this again come morning. Something´s gotta give at some point…been at this for days

It does sound like you continue to have air in the cooling system.

Of course it would make the most sense to follow the coolant air bleeding procedure in the factory service manual. Absent that, jack the front side of the vehicle up, put the front wheels on ramps, etc, anything to get the top of the radiator to be the highest point in the cooling system. When you achieve that, unless there are special bleed ports needing manual opening on this engine, usually all you have to do is open the radiator cap (the one on the top of the radiator, not the one on the expansion tank), turn on the heater flow to max, and idle the engine until the thermostat fully opens. As the air escapes the coolant level may drop in the radiator, so be prepared to add some pre-mixed fresh coolant.

If you feel the two hoses going through the firewall to the heater, one of them should feel hot, and the other not as hot. You can always disconnect the one from the engine to the heater temporarily as a test and verify it has a good strong flow. If there’s no flow in that hose, that could be the water pump or thermostat not working correctly.

If all that doesn’t work, probably next thing I’d try is to replace the radiator cap with a new one. And if all that fixes the engine overheating problem, but you still have no heat, next guess would be a binding blend door or failed actuator.

Are you sure that you put the thermostat in correctly. I think you put it in upside down.


Some types of thermostats have two orientations you have to get right for them to work correctly: Up/down, and Inside/outside. It’s easy to do it wrong since 3 out of 4 of the possible ways to install them are incorrect.