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John Mc
John Mc, Ford Technician
Category: Ford
Satisfied Customers: 6240
Experience:  19 years Ford Lincoln Mercury experience
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1999 f150 5.4 Apparently plugged heater core. Can it be flushed?

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1999 f150 5.4 Apparently plugged heater core. Can it be flushed? Symtoms: No heat, turn blower off while driving, wait 30 secs or so, turn blower back on and get heat for a few secs, then cold. Could it be blower is cooling core faster than water is circulating thru core?

Hello, I am John, a Ford dealer technician.

I hope I can help solve your problem quickly and accurately.

 

It is very possible you have a plugged heater core. This is common on these trucks. Sometimes you can flush them but you have to do it directly. This is how to do it. Take one of the hoses loose from the heater core. Use a pair of pliers and pinch off the open hose back about 3 inches from the connector. Open the drain on the radiator. Now use a garden hose and push it onto the heater core. If it won't fit you will need to cut the hose and clamp it on. Turn the water on high. Let it run for 5 minutes or so. Repeat with the other side of the heater core. Now drain the system and refill with a 50/50 mix of green coolant and water. If it still doesn't work you will need to replace it because it is too stopped up.

 

I have never seen a v8 f150 have a problem of low coolant flow so I don't believe this is your problem. The only other problem I have seen is where the temperature blend door itself is cracked and causes lack of heat problems. The difference is this won't even get hot for a few minutes. This leads me to believe that you are dead on you diagnosis.

 

If you have any more questions please feel free to ask, it's what I'm here for!

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Thank you,

John Mc

JustAnswer Expert

John Mc and 7 other Ford Specialists are ready to help you
Customer: replied 6 years ago.
John, When I said low flow I was referring to the flow thru the core itself, not the system. One more thing. Do I have to get new ends for the hoses? I think they use a special connector. I did have a bad blend door but I replaced it last year with a stainless steel one that a guy sells on ebay and you can change it thru the glove box. Trick setup.

I got you on the low flow ;) Sometimes the tabs break on the connectors. You just have to replace the tabs. You just squeeze the tabs, twist and pull and they come off. Not always that easy but as I said sometimes they break. You can get new ones at a dealer for around $5 a connector. Easy to install. Never heard of the ss blend door, that sounds cool!

 

If you have any more questions please feel free to ask, it's what I'm here for!

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important to me so please leave accurate feedback for others to see my job performance.

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Thank you,

John Mc

JustAnswer Expert

Customer: replied 6 years ago.
I can't figure out how to add positive feedback. You deserve it, John

Thank you! I'm contacting the moderators to see if they can help you leave feedback. They should contact you via email shortly.

 

Thanks,

John Mc