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dodge truck is overheating, heater won't blow hot air
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dodge fixer
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Nov 8, 2008, 4:13 PM
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dodge truck is overheating, heater won't blow hot air
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Hello folks
I have a 2002 dodge ram 1500 v8 4.7 ltr. replaced the radiator and thermostat, still overheating, and the heater will only blow hot air for a short period of time. Any advice would be greatly appreciated. blower still works just air gets cold.
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Loren Champlain Sr
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Nov 8, 2008, 4:43 PM
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Re: dodge truck is overheating, heater won't blow hot air
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Did you replace the radiator and t-stat because it was over-heating to begin with? You may have an air pocket in the heater core (assuming it was getting hot, before). Although rare on this engine, you may also have a head gasket leaking hot exhaust gasses into the cooling system which would 'super-heat' the coolant quickly and cause the heater problem. Assuming the engine is no longer over-heating, I would suspect an air pocket. If so, allowing the engine to run long enough for the t-stat to open and close several times will normally work the air out. I've had to raise the front of the vehicle (so any trapped air goes toward the radiator) in order to work out the air. Good luck. Have a great weekend (after you get it figured out). :)
Loren
SW Washington
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Tom Greenleaf
Ultimate Carjunky
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Nov 8, 2008, 5:12 PM
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Re: dodge truck is overheating, heater won't blow hot air
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Hmmm? Agree with Loren about the exhaust gasses are still getting in. If this was ever really filled properly and usually if heater works you are approaching full of coolant and still overheating with the no heat problem then it's probably boiling hot and the air (vapor of boiling) doesn't allow heater to work. How overheated does it get? Are you letting it boil right over like a steam kettle and needing to refill again? This should purge out air from a coolant refill on the first cycle and not be fussy as some vehicles are. So far I think this is a head gasket problem and that won't make your weekend!
T
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dodge fixer
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Nov 8, 2008, 6:11 PM
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Re: dodge truck is overheating, heater won't blow hot air
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thanks for the info i'll try anything at this point!!!
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Loren Champlain Sr
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Nov 9, 2008, 10:20 AM
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Re: dodge truck is overheating, heater won't blow hot air
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Dodge fixer; It is very common for DIYers to install the t-stat upside-down. You may want to check, just to be sure. If you did, don't feel bad. We've all been there. That's a part of learning. Another trick, which Tom had posted in another thread, is to drill a 1/8" hole in the flat area away from center on the t-stat flange. (wish I could add a drawing). This allows a bit of flow, even when the stat is closed, and aids in bleeding the air.
Loren
SW Washington
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Tom Greenleaf
Ultimate Carjunky
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Nov 9, 2008, 11:09 AM
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Re: dodge truck is overheating, heater won't blow hot air
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 Lookie what I found out there! The light dot (is actually a tiny barbell) is called a "jiggle valve" used in some thermostats to assist in getting air out but not allow too much bypass for poor heat or slow warmups. Hard to find these and if you have one the dot goes up top - sprind end always toward block. You can drill a tiny hole for serious problem engines to allow easier air removal. Some will have an notch already cut in which goes un-notices to do the same thing. If they work then filling a system will be close to purged but still a wait for air to pass by the closed thermostat.
As Loren said - thermostat must be known installed properly. They will misbehave if backwards and then might open after too hot and behave a short time and repeat that. Many simply won't fit backwards and can't say for this application.
Added note: VERY few thermostats have been truly defective in my findings. A new one coupled with a new radiator that still overheats suggests air involvement for any reason.
Way out there is pump that doesn't pump (corroded impeller) - not common at all but has been reported - not this engine BTW. Those usually dislike low rpm at first.
Keep at it and checking. Avoid overheats,
T
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Loren Champlain Sr
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Nov 9, 2008, 11:17 AM
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Re: dodge truck is overheating, heater won't blow hot air
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Okay, where are you finding all these cool pics? That's cheating!
Loren
SW Washington
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dodge fixer
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Nov 11, 2008, 7:05 PM
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Re: dodge truck is overheating, heater won't blow hot air
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thanks again have checked out these suggs. but still running hot, now i am looking for the heater control valve which could possibly be stuck?? sound like a possibility to you guys?
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Loren Champlain Sr
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Nov 11, 2008, 7:22 PM
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Re: dodge truck is overheating, heater won't blow hot air
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Sorry, your truck doesn't use a "heater control valve". And, that wouldn't cause an overheating condition, anyway.
You can check for a head gasket leak a couple of ways. There is a chemical called "Block Check" available at NAPA or CarQuest stores. The chemical will turn from blue to yellow if exhaust gasses are present in the cooling system. The other way would be to "sniff" the cooling system with a gas analyzer for hydrocarbons. Have you visually checked the t-stat to make sure it is properly installed? (see Tom's earlier post; It shows a t-stat, right side- up). As new as your vehicle is, I doubt that it could be a plugged radiator, but in this world, anything is possible.
Loren
SW Washington
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