Heater issues

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smdk2500

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Hello I have a 95 k2500 with the 5.7 My issue is when the truck is idleing the heater works great. The temp gauge reads right below the 210 degree mark. When i drive roughly a 1/4 mile down the road the temp drops to halfway mark from 100 to 210. It will warm back up to below the 210 mark and then drop again. This is telling me that the tsat is working. While the temp is fluctuating I have very little heat. Luke warm is hot compared to what i have. I have replaced the tsat twice and have bleed the system correctly . Truck has new radiator water pump and hoses. I did not have this issue last year. I have tried covering the radiator with cardboard and that doesn't help. I don't know if the fan clutch could be causing this but at this point I am grasping at straws. Any help would be greatly appreciated.
 

Supercharged111

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Stat should kill the flow and regulate temp regardless. What kind of stat and what ambient temps?
 

Eveready

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Hello I have a 95 k2500 with the 5.7 My issue is when the truck is idleing the heater works great. The temp gauge reads right below the 210 degree mark. When i drive roughly a 1/4 mile down the road the temp drops to halfway mark from 100 to 210. It will warm back up to below the 210 mark and then drop again. This is telling me that the tsat is working. While the temp is fluctuating I have very little heat. Luke warm is hot compared to what i have. I have replaced the tsat twice and have bleed the system correctly . Truck has new radiator water pump and hoses. I did not have this issue last year. I have tried covering the radiator with cardboard and that doesn't help. I don't know if the fan clutch could be causing this but at this point I am grasping at straws. Any help would be greatly appreciated.


It definitely sounds like the exact symtoms of a stuck open thermostat. Get a different brand and try again. I think you lucked into a run of defective parts.
 

smdk2500

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Stat should kill the flow and regulate temp regardless. What kind of stat and what ambient temps?
The stat is from car quest so indont know for sure who makes it. The ambient temps have been in single digits. Before they dropped to single digits everything worked correctly.
 

Eveready

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If it works OK except in single digits a redneck fix would be to to duct tape a piece of cardboard box over about half the front of tbe radiator. Just remember to remove it after the weather warms up.
 

smdk2500

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If it works OK except in single digits a redneck fix would be to to duct tape a piece of cardboard box over about half the front of tbe radiator. Just remember to remove it after it warms up.
I already have it covered. I'm going to try a differnt stat when i get off work. it's just frustrating im a mechanic for a day job and something this simple is getting the best of me.
 

Bob L

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Remember that new stands for never ever worked. I got a new coil from Car Quest once that was a dud and tore my hair out looking for the no spark problem till I tried an old coil.
 

ram1220

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Had the same issue with a new stat from Autozone. Defective from the start. Ordered a different brand from Rock Auto and problem solved.
 

smdk2500

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Well I think I have finally got my heater problem fixed. Replaced the stat with a 3rd from a different parts store. After i replaced it I powered washed the engine. Ran great while I bled the air out. Started to pull away engine stalled would not restart. Found the ignition module crapped out. 235k on the original part I figure it had a good run. Now it idles rough coughs and sputters while driving. I had it backfire once through the throttle body while accelerating. Now has a check engine light but I cannot pull the code. When in high idle when its first started it idles at about 1600 rpm. Ive never had it do this. It will drop down to normal but it will sometimes will idle up to 1100 for a few minutes and then back down for a few minutes and back up. I know vacuum leaks will cause a high idle but I cannot find any. Are there any other ways other then a code reader to pull the code. And yes I do have the obd1 connector for my scanner. I was able to connect to ecm while i was trying to figure out the module problem. Now I cant connect. Anyone have any ideas till I can get the code pulled.
 

smdk2500

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well I searched and figured out how to pull the code with out a reader. It is throwing code 21 which is the tps code. Now to figure out why its throwing that.
 
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