No Heat at Idle sometimes

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Eightiesrock80

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I’m guessing there is an air bubble somewhere in the system I’ve taken the over flow cap Off many times to try and let air out of the system I can’t seem to get enough air out is there a bleeder valve for the coolant system on the 5.4 can anybody help I need heat I got a little girl. this truck is like brand new even though it’s a 2003
 

BRIANGEE

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So it's only at idle and then only intermittently? Maybe it's just the thermostat sticking closed.
 
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99WhiteC5Coupe

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I’m guessing there is an air bubble somewhere in the system I’ve taken the over flow cap Off many times to try and let air out of the system I can’t seem to get enough air out is there a bleeder valve for the coolant system on the 5.4 can anybody help I need heat I got a little girl. this truck is like brand new even though it’s a 2003


Your coolant is probably low in your radiator. Do not check the level in the overflow jug - check the radiator when it is cool. When your engine slows to idle, there is not enough hot coolant flow (due to a low level) to keep the heater core and HVAC discharge air hot.

You could have a bad radiator cap, and/or an coolant reservoir jug HOSE that could not be tightly fastened or have pin holes in it. When the engine cools, it draws coolant from the reservoir back into the radiator. If the cap is bad or the hose has a leak, it will draw air into the radiator.

Is your upper coolant hose collapsing (even partially) when the engine cools? If so - it is a classic sign of a bad radiator pressure cap.

If your radiator is low, you probably have a slow leak somewhere.
 

99WhiteC5Coupe

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I think the radiator is sealed. I see no cap. And the truck does not leak any any freeze.


It is possible to have a small leak and no obvious signs of the leak, especially if the leak is low and only drips when the engine is hot and driven. It can also have a small internal engine leak, which causes the coolant to be burnt in the combustion chamber.

I own a 2015 Epediton Limited with the 3.5 Ecoboost V-6. I don't own a 2nd gneration model, so I can't look at the radiator to determine if it has a radiator cap.

Perhaps someone else will chime-in soon.
 

Bedrck47

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There is no cap on the radiator itself The Cap is located on the overflow reservoir.

You don;t want the reservoir COMPLETLY full there is a mark on the side of the take the says cold water fill that is where the water level should be when the engine is cold

Also top of the water using distilled water ONLY
 

Bedrck47

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After the engine warms up check the inlet and outlet hoses to the heater core they should be about the same temp if not you could have a clogged heater core

The engine temp gauge in the instrument cluster should reading about half way if noy then you could have a t/stat problem or water pump problem
 
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