‘99 Exp 5.4 4X4 no heat?!?!

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Tacsat117

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Hey all. Just before winter set in the heat stopped. Local shop replaced leaky radiator, heater core, thermostat , and by passed the rear heater core, but still no heat. The truck probably has 260k on it and came from New Mexico. It probably has never had the cooling system flush. Local shop reports “a ton” of rust each of the three times they have tried to flush it out. Do you all have any idea what else we can try?
 

Hamfisted

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Why'd they bypass the rear heater core ? That might be the only place you DO get heat from until you get the front straightened out. Are your front heater hoses hot ? If they're both hot you might have a blend door actuator problem, where the blend door is not opening to let the hot air through. Hopefully they would've checked that when they replaced the front heater core, but who knows.
 

AZShawn

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I second blend door actuator. If you had the front heater core replaced and both tubes from the heater core are hot, its got to be something stopping the blend door from switching to the hot side. It may not be the actuator itself (but that's where I would start) but its got to be blend door related.
 

Yupster Dog

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Local shop replaced leaky radiator, heater core, thermostat , and by passed the rear heater core, but still no heat.
Get them to flush the new heater core. When i replaced radiator it had something in it (looked like little black b@lls) only found out when i flushed the heater core.
 
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Tacsat117

Tacsat117

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Thanks all,

I’m taking it back Saturday and I will have them check to see if the hoses are hot and have them check the blend door!
 
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Tacsat117

Tacsat117

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We’re still at it. It was blowing hot for a bit then it seemed to plug again. I’m guessing the cooling system was never flushed out. The old owner didn’t seem to do much maintenance. The shop said they flushed it until it ran pretty clear. I’m wondering if the water pumps blades have corroded to nothing so there not enough pressure to blow through clogs. When I drive it it will start blowing cold, but if I down shift for higher RPMs it will blow hot again. Should I replace the water pump? I’d love to keep the truck for a few more years, but without heat it will be a sad winter!
 

Aspen03

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That's an impressive amount of wear. I'd think that if it impeded water flow so much you got no heat that the cooling system wouldn't even be able to do its job or you just got very lucky with just enough flow for essentials
 
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Tacsat117

Tacsat117

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The engine temp, even in the New Mexico summer when I got it 10 years ago has been solid up till just a bit ago. I hope we get some good heat now!
 
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