intermintent heat please hep!!!!

[crash11x]

got a 04 ford f250 egr delete with 114,000 miles. i am only getting heat when i drive down road and as soon as i come to idle it turns cold. i have replaced water pump, thermostat, took heater valve out of heater core line and replaced with a manual ball valve, and also flushed my heater core. im not loosing a drop of coolant and its topped off. could i be having a vacuum pump problem not opening doors in cab or what? also when i put tuck in 4x4 it only blows out defrost? what is going on?

[kinnisoj]

I was gonna say it sounds like a slipping water pump but you say you replaced that...are you still getting air flow at idle (through the vents)?

[crash11x]

Yes I get air flow but its freezing cold air.

[kinnisoj]

If it goes from hot to freezing cold ( or outside air cold) very quickly its running out of hot coolant to heat the air. Wonder if you have air in the system?

[zman111]

Not sure how you check to make sure or get air out of the system ? But here's an idea for you to check. Have someone check the Resivor cap to make sure it holds the correct pressure if not replace it, I'm thinking if the cap does not hold the correct pressure the system can't build pressure? Let me know if this works for you.


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[sargar]

It sounds low on coolant to me. Do you ever get a "water fall" sound from behind the glovebox? If you suspect air in the system find someone with an airlift or see if parts stores rent them. It pulls a vacuum on the system, sucking the hoses flat, then uses the vacuum to pull the coolant in.

http://www.thetoolwarehouse.net/p-73...ew-550000.aspx

This tool is a life saver!

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[crash11x]

i have ran it for about 30 miutes with cap off to let the system burp itself. also if my cap was bad how would i check that. not more than a year ago i bought new degas bottle and cap

[kinnisoj]

Caps are cheap...buy a new one juz for fun.

[lugnut]

do a search on here and do a coolant pressure test for failing head gaskets. its fairly easy to do. i had the same exact problems with my truck. i also replaced all the same parts you did and also never lost any coolant. but... my cooling system was hitting 24 psi. truck still ran good too. but i had blown headgaskets. i just had them replaced and now my heat works great. no more using a gallon of washer fluid to clear the frost off my windshield in the morning. i hope this is not your issue.