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No heat after flush

Tiny
ROBERTBARNES62
  • MEMBER
  • 1999 FORD EXPEDITION
  • 4.6L
  • V8
  • 2WD
  • AUTOMATIC
  • 195,000 MILES
I flushed my radiator and now I have no heat. While I was flushing the radiator it was blowing very hot and now that I have finished the flush and filled with coolant it blows a little warm for about five minutes and then it starts blowing cold.

Please help!
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Wednesday, November 15th, 2017 AT 4:33 PM

8 Replies

Tiny
HARRY P
  • MECHANIC
  • 2,293 POSTS
Gunk freed up in the cooling system when you flushed it probably got into the heater core and clogged it up. Under the hood, there are two cooling system hoses going to the firewall. One is an inlet going into the heater core, the other is an outlet. Take both hoses off, point one somewhere where coolant coming out will not get on important electrical stuff. Take your water hose and connect it to the other hose. Then turn the water on, low pressure, and let it run until the water coming out of the core is clean. Then let it run for a couple of minutes. Reconnect the hoses, take the radiator cap off, and start the engine. Turn the heat on, full blast. Let the car idle and keep pouring coolant into the radiator every time the level drops. Do this for about fifteen minutes, and then you should have all of the air bubbles out of the system.

This process will clean out the heater core and bleed any air bubbles out of the cooling system. Let us know what happens.
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Wednesday, November 15th, 2017 AT 7:18 PM
Tiny
ROBERTBARNES62
  • MEMBER
  • 83 POSTS
Ok, sorry it took so long to update but the holidays were great as always. I did as described and you were right in that there was gunk in the heater core. I flushed it and caught the first little bit in a bucket just to see what was in there, it seemed to be rust or dirt.I then allowed it to flush for about 15 to 20 minutes and the water was clean and seemed to be free flowing. I then reattached the heater hoses and allowed the SUV to run for about 15 or 20 minutes with the truck parked on a hill, rad cap off and heater on full blast. At that point it was heating really well. The next day I drove the SUV in the morning and it heated up fine but then after about 5 minutes of driving it started to blow cold air. I then went to mcdonalds and as I was sitting in line it started to blow really hot again, then half way home it started to blow cold air again. I have driven the SUV about 5 or 6 times since then and it is still cycling between hot and cold every 5 to 10 minutes. I am so lost as to what the problem could be.
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Monday, November 27th, 2017 AT 10:27 PM
Tiny
HARRY P
  • MECHANIC
  • 2,293 POSTS
You might have to do it again. Also, what's the temperature gauge doing? You might need a new thermostat. Does the temperature drop when you drive?
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Tuesday, November 28th, 2017 AT 4:39 AM
Tiny
ROBERTBARNES62
  • MEMBER
  • 83 POSTS
The temperature gauge is in the normal operating range and does not drop while driving. I will flush it again and replace the thermostat as well this time. One I do all this I will leave feedback as to if it worked or not.
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Tuesday, November 28th, 2017 AT 5:00 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 42,840 POSTS
It sounds like you may have the beginnings of a blown head gasket which is forcing exhaust gases into the cooling system which make the heater stop working.

Can you run this test and get back to us?

https://www.2carpros.com/articles/head-gasket-blown-test

This guide may help as well

https://www.2carpros.com/articles/car-heater-not-working

Please run this test and get back to us.

Cheers, Ken
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Thursday, November 30th, 2017 AT 12:19 PM
Tiny
HARRY P
  • MECHANIC
  • 2,293 POSTS
Good point Ken, that's a definite possibility. If that's not it, then I think we'll have to look into issues with the HVAC control head, blend door, and associated actuator. If that's the case then I'll dig up what information that I can find.
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Thursday, November 30th, 2017 AT 5:53 PM
Tiny
ROBERTBARNES62
  • MEMBER
  • 83 POSTS
Hello, sorry it took so long to get back but I did fix the problem. I noticed the water pump was weeping water so I replaced the water pump and now the heat works great and does not cycle from cold to hot. I am guess the water pump was half way working thus not sending water through the engine and that is why the heat was cycling back and forth between hot and cold. Thank you guys for all the help!
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Monday, March 5th, 2018 AT 6:58 PM
Tiny
HARRY P
  • MECHANIC
  • 2,293 POSTS
Ahh with the pump weeping you were getting air bubbles in the system, hence the "cycling" that you were feeling. Makes sense. Glad to see you got it fixed. Please feel free to come back any time.
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Tuesday, March 6th, 2018 AT 3:35 AM

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