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Anyone have any idea why my heater will only blow out hot air when my car is moving? If I stop at a red light or such, then it blows out cold air. It's an almost instantaneous switch from hot to cold.
 

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Could be an actual problem like low coolant, bad thermostat, or bad water pump. My car does this too, but I know for sure that my coolant system works. I think it's just that the engine doesn't stay warm enough while idling in winter and the thermostat closes to keep the engine warm unless you've been driving for quite a while with constant load on the engine.
 

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BoomGoesTheDynaMitt
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I would try filling (@ the radiator) then burping the coolant system to see if that helped. I think it will.
 

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QuickSLVR
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I also have this same problem, and my thermostat and water pumps are new and i know its not the coolant since i recently flushed it. The more I drive the hotter the air is and when i turn it off it still blows heat through the vents, but not as much as it was on 1
 

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(b)org banugee
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There's air in the line. It doesn't matter that you flushed it. Whomever did the flushing got air in it.

Fill the radiator at the cap while it's hot and running, and then burp it.

If that doesn't work, start worrying about other causes.
 

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I'm Working On It...
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There's air in the line. It doesn't matter that you flushed it. Whomever did the flushing got air in it.

Fill the radiator at the cap while it's hot and running, and then burp it.

If that doesn't work, start worrying about other causes.
isn't that dangerous? I would think that while the coolant is hot and under pressure it would be a bad idea to loosen the cap....
 

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New daddy
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you run the car upto temp with the cap off and the front of the car raised slightly.
Bitter is right. The radiator cap needs to be the highest point in the system for the air to come out. The way the car sits the heads are higher than the radiator. A steep hill with a curb on the side works great. Just pull the passenger side front tire onto the curb. Also, make sure the heater is on in the car when attempting to burp the coolant.

BTW, my car was slow to warm up a couple years ago. I bought a thermostat from the dealer and it fixed the problem.
 

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BoomGoesTheDynaMitt
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You squeeze the hell out of the upper and lower hose with the radiator cap off when the car is warm to get air bubbles out.
To my knowledge you just squeeze the lower hose. Just grab it and squeeze it several times with the engine running. This will basically push the air pockets out of the system (the air will leave through the open thermostat hole).
 

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did burping your Rad fix this? my car does the same thing, blows hot air when I am moving but once i stop it goes back to cold, even when operating at proper running Temp.

Let me know if you got this fixed, cause if so I'll go burp my car right now. Cold weathers here and i dont like having to rev my car to stay warm at stop lights and in traffic
 

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I burp every time I flush the coolant, and most times it stays warm. When it's too cold outside, the thermostat closes back up unless I've been driving for a while, though. If it still blows cold air after a good 10 minutes of driving, burp it. Otherwise I'd say that even though the temp gauge is in the middle, you're just on the bottom verge of where the thermostat opens, so the wax in it is expanding and contracting every time you put a load on the engine.
 

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Yea my temp gauge is never in the middle its always like a 1/4 inch below the middle. Im going to burp my RAD tonight when i get home so i got a hill to do it on. if that doesnt fix it would running a thermostat thats opens at a lower temp fix it and not damage anything? just wondering thanks for the help :worship:
 

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AHHHHHH!!!
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Anyone have any idea why my heater will only blow out hot air when my car is moving? If I stop at a red light or such, then it blows out cold air. It's an almost instantaneous switch from hot to cold.
Yes, there is air trapped in your heater core.

Use this radiator funnel (it works) and its the right way to burp your cooling system.

 

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You usually want to use a lower temp thermo in the summer to keep the engine cooler. In the winter, it *can* lead to longer warm up times and your heater blowing less-than-hot air.
If you get a thermo, get the OEM one with the jiggle valve. I put in a cheep thermo and it didn't last a year.
 
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