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Old 09-06-2011, 01:49 PM
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Heater blows cold

Hey guys i have a 2004 6.0 with 127000 miles on it. My issue is when the trucks is warmed up and im driving down the freeway or under lite load the heater/defroster blows warm. Then when i let off or am sitting at a stop or idling it starts blowing cool air like almost a/c cool. It pukes if i put too much coolant in it i think it suppose to be 1/4 below the min line. It doesnt really puke now im running stock file with afe intake and exhaust. I was running erics files but im almost certain my egr cooler and oil cooler are toast. So im trying to baby it tiil i can fix it all. My question is do you think its egr related or headgasket related. Or possibly heater core or thermostat? If i add coolant it doesnt do it as bad until it pukes. Thanks for any help and sorry for the long post.
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Old 09-06-2011, 05:04 PM
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Dont qoute me on it but I think there is a heater control valve on the heater tube. I beleive its vaccum operated. I know the stock gauges suck but are you seeing higher tems between the two driving styles?
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Old 09-06-2011, 06:22 PM
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The same crud that plugs the oil cooler can plug a heater core. Maybe at idle you are not moving enough water through the core. You can try removing both heater hoses and GENTLY backflushing the core with a water hose. Invest in a couple of pinch off pliers to keep from losing too much coolant from the heater hoses and stick an extra piece of hose on the core so that you are not dumping coolant/water/goo all over your engine. Try to catch it in a bucket so that you can see what kind of nasty comes out. Post it if this works.
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Old 09-06-2011, 07:50 PM
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Quote:
Originally Posted by sargar View Post
The same crud that plugs the oil cooler can plug a heater core. Maybe at idle you are not moving enough water through the core. You can try removing both heater hoses and GENTLY backflushing the core with a water hose. Invest in a couple of pinch off pliers to keep from losing too much coolant from the heater hoses and stick an extra piece of hose on the core so that you are not dumping coolant/water/goo all over your engine. Try to catch it in a bucket so that you can see what kind of nasty comes out. Post it if this works.
Ill go a couple steps further.

Typically when i get a truck that has bad head gaskets, you can go out romp the hell out of it, depending on how bad they are, the truck can lack power, emit smoke, and the temp gauge never gets more than 1/8th of an inch off of C and the heater is blowing ambient air or cool air. Can also have erratic heat.
The vacuum hose to the heater control valve is a joke really... Ive seen where someone has been in there before me left it unplugged and either plugged it onto the heater core box, or left it on top of a very hot intake/valve cover and it melt shut, that really doesnt have an effect on the operation of the heater core... I believe that was for EATC units only aiding in keeping the temperature in the cabin regulated to what temp you wanted it set to...

Without it it sticks wide open and has full flow going through the heater core.

Now if you suspect a failed egr cooler, remove the egr valve does it look gummy and wet in the intake? Do you notice it puking only when you run it hard or does it puke no matter what? If its puking only when you run it hard-head gaskets. If it pukes when you puss foot or hammer down-EGR cooler.

Best way to find out make my gauge up and test it. if it builds pressure from Idle+ egr cooler. Builds pressure above 17psi when held wide open Head gaskets.
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Old 09-06-2011, 09:25 PM
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Thanks for the reply guys. Ill try out thee tests and see what i get. I dont have gauges right now so im kinda blind gping off the dummy temp gauge. The factory gauge says its warmed up. *** far as puking goes. For example if i top off the coolant a go romp it it pukes. Then i can hot rod it and it seems to be ok. Maybe very little puking if any after the intial puke. It never does it just normal driving no white smoke or any smoke for that matter. I can kinda smell coolant when i park the truck and get out near the drivers side fender also the degas bottle is nasty like sludgy booger crap. Oil in the coolant im assuming. Ill check egr valve wetness tomorrow should i replace gasket and o rings on valve ive already pulled and cleaned it recently within the past year. And replaced them it unplugged now thanks again
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Old 09-06-2011, 09:29 PM
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Im just trying to nurse it until the end of the year then hopefully do studs egr delete oil cooler coolant filtration etc. im just trying to pinpoint if i can cheaply get heat before winter like maybe its something simple. If not ill ride dirty in a jacket and beanie to work. I just dont want it to crap out before i can fix it.
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Old 11-01-2012, 12:56 PM
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I have an 04 that I recently did a delete on. This morning I was only getting cold air even after it got to operating temperature. after I got home I opened the hood and on the passenger side valve cover there is a vacuum switch. I presume it is the blend switch. I removed the vacuum line and the valve closed, started it up and low and behold it was blowing hot air. Reconnected the vacuum line heater went cold again. Now I must decide if it`s the valve or the switch on the dash.
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Old 11-01-2012, 03:02 PM
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Quote:
Originally Posted by Lastcaveman View Post
I have an 04 that I recently did a delete on. This morning I was only getting cold air even after it got to operating temperature. after I got home I opened the hood and on the passenger side valve cover there is a vacuum switch. I presume it is the blend switch. I removed the vacuum line and the valve closed, started it up and low and behold it was blowing hot air. Reconnected the vacuum line heater went cold again. Now I must decide if it`s the valve or the switch on the dash.
The valve that you found should only close when you have selected recirc/max AC. If you are getting vacuum to in normally you have something funny going on, maybe the selector switch on the climate control.
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