2006 Ford Focus How can I flush the heater core?

Question: Are the heater hoses to the heater core attached to the cylinder head easily accessible from the top? Are they below or near the battery box?

My 2006 Ford Focus heater is blowing cold. It has been progressively worse (not so hot air) over the last few years, and now it seems like the heater core is blocked. It was barely warm enough last year in the Boston winter, so I knew this was going to happen. (I just thought I would be able to get one more year out of it, before I sell it next year.)

I located the heater core. The two hoses connected to the heater core are visible from the top. But they seem to be almost impossible to reach, either from the top or bottom. So, I am thinking it might be easier to reach the other ends of the heater hoses–where they are connected to the cylinder head. I am thinking they are attached at the rear of the cylinder head, where there is the battery and the air intake box. Am I correct? Are they relatively easy to access?

Before you go thru all that, why not take the vehicle to a shop and have the cooling system flushed?

They’ll hook a flush machine to the vehicle and see if that clears the heater core. And if it doesn’t, they’ll add a chemical formulated to clean the cooling systems and try flushing again.

And if that doesn’t work, the heater core probably needs replacing.


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You may not want to flush it yourself. Ford heater cores usually leak. It’s about four or five hundred dollars to have it replaced. So, disturbing the heater core may not be a great idea. Maybe they have improved lately but I have doubts.

I have never owned a Ford, but every car I have ever owned has/had the heater core completely buried inside the dash, and not serviceable from under the hood. To get to it would require a complete disassembly of the dash, etc.

If I could have a heater core correctly replaced for $400-500, I would JUMP on that! I think your estimate is about $1000-1500 too low, unfortunately.

@Roger124 - You are asking questions that make me think that this flushing might be beyond your abilities. Do you have a safe way to raise vehicle if needed ? How to you plan to dispose of the drained fluids ? Antifreeze is poison to animals . Do you know how to bleed the cooling system ? At least get a few places to give you some idea what it would cost to do this flush.

Side note : Why wait a year to replace this vehicle , this is the time when discounts on 2019 vehicle start and low financing .

my 06 taurus had a steel “H” shaped bypass assy on the firewall. i do not know if the focus is setup the same way. yes the car has a 15psi system max and a garden hose could see 60psi? you could use a small external pump to recirc fluid thru the heater core as that would be lower pressure.

I would ask how you know it’s the heater core. I don’t see any mention of what has been done to narrow it down to the core. I wouldn’t pay for anything until I did some basic free diagnosis. Is the engine getting up to normal temperature? If you have a temp gauge, is it in the normal range after the engine has had enough time to warm up? If not, perhaps your thermostat is stuck open. If it is, then feel both hoses going to the heater core. Are they both hot? If so, perhaps the problem is with the blend door that mixes hot and cold air. If one is colder, perhaps you have an obstructed core but make sure your car does not have a diverter valve first. Some cars have a valve that controls hot water flow to the core but those are becoming more of a rarity these days from my experience.

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