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1999 F150 5.4l NO HEAT HELP

1999 F150 5.4l NO HEAT HELP

  #1  
Old 11-29-2018, 07:48 PM
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1999 F150 5.4l NO HEAT HELP

I have a 1999 F150 5.4l. The heater stopped blowing cold air. I verified the blend door is operating correctly. I flushed the heater core....had a very small amount of brownish water before it went completely clear. I flushed it from both sides. I flushed the motor and have clear good flow throughout. I verified the thermostat is operating correctly. I noticed after the motor warms up the inlet side hose to the heater core only warms up half way. Near the motor it is warm....near the heater core inlet it is cold. The return hose is completely cold. Has anyone experienced a water pump failure that would cause this???? Help I'm at a loss!!!
 
  #2  
Old 11-29-2018, 07:52 PM
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The impeller blades could be gone or it internally came apart.
 
  #3  
Old 11-29-2018, 08:04 PM
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I am going to pull the pump tomorrow....hoping that's the issue!
 
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Old 11-29-2018, 08:05 PM
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You mean it stopped blowing warm air, right?

I think there is a restrictor in the hose assembly before it gets to the core. May want to check on that.
 
  #5  
Old 11-29-2018, 08:08 PM
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I flushed it from both sides.
How much of the hoses did you also flush?
 
  #6  
Old 11-29-2018, 08:23 PM
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All of them....I actually replaced both of them
 
  #7  
Old 11-29-2018, 11:09 PM
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Good.

Then you've either got an air bubble in the heater circuit or the pump ain't pumping.
 
  #8  
Old 11-30-2018, 02:51 PM
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Originally Posted by projectSHO89 View Post
Good.

Then you've either got an air bubble in the heater circuit or the pump ain't pumping.
I burped the system before and after...same issue.....looks like I'm changing a water pump this weekend lol.
 
  #9  
Old 11-30-2018, 03:42 PM
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I'm surprised that it's not overheating if the water pump is shot...............
 
  #10  
Old 11-30-2018, 06:48 PM
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Welcome to the wonderful world of Ford truck heaters. You have the same deal as I do but like mine that tows in 100 degree heat just fine, it likely is not the water pump.
 
  #11  
Old 12-01-2018, 10:01 AM
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A couple summers ago my truck starting to have the temp hand start raising slowly if I was in a drive through or in traffic for a few minutes, you could actually rev it up a little and the hand would start coming back down. Replaced water pump and only one impeller was left and it was about gone. Pump was original with over 230,xxx miles on it.
 
  #12  
Old 12-01-2018, 11:25 AM
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If you use tap water in the cooling system, it could plug up or partially plug up the heater if the water is hard in your area. After plugging up a heater core a long time ago and had the joy of replacing it, I started using distilled water to mix with the anti-freeze.
 
  #13  
Old 12-01-2018, 11:27 AM
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x2 on Roadie's suggestion. I always use bottled distilled water on coolant flushes OR premixed 50/50 setups.

I still have a feeling it is the impeller on the water pump. Just dealt with one not too long ago.
 
  #14  
Old 12-06-2018, 07:32 PM
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Turns out the problem was indeed the water pump. Truck never overheated....even in 98deg Florida heat. No idea how it didnt.
 
  #15  
Old 12-06-2018, 08:12 PM
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Congratulations on the repair of your truck! And thanks for letting us know!
 

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