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Hello everyone. I have been researching about my heat issues and have not gotten much help. I have an 03 Murano that recently started sounding like water would rush under the passenger side floor board when I would take off from a stop and the heat would get cold when I was at idle for a period of time. I searched and found that I probably had an air pocket in the system. I burped the system and all was perfect for a few weeks. Then I noticed the sound again and the loss of heat. I went thru the motions of burping the system again and all was fine for a few days and now I have air in the system again. I noticed that my overflow tank was filling up after each time I had this issue. I replaced the radiator cap and burped the system again. A few days later I have air in the system again... I do not have the typical blown head gasket issues. No coolant in the oil, exhaust is not steaming any more than normal in cold weather, only adding coolant to the radiator because its being pushed into the overflow tank which creates an air pocket at the heater core so when the car cools down it doesnt have room for the overflow tank to return the coolant due to the radiator appearing full. Can anyone give me suggestions??? I am at a total loss on this one. Never had issues like this with any other car I have ever owned.
 

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I'm wondering about a coolant leak which isn't going into the oil. That would fit the symptoms.
 

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Not heard of this one but, I would visually check the heater valve - located by the firewall - if its working (opening and closing when temp knob is switched from heat to cold and vice versa). This would cause your ac to stop putting out hot air if its randomly not opening up. Unfortunately, I think the valve is hard to see and get at- you might need to remove the cowl. Good luck.
 

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I'm wondering about a coolant leak which isn't going into the oil. That would fit the symptoms.
But it is never truly low on coolant. I thought the same thing since it isnt in the oil but it isnt using coolant either. Just pushing it into the over flow tank....

Not heard of this one but, I would visually check the heater valve - located by the firewall - if its working (opening and closing when temp knob is switched from heat to cold and vice versa). This would cause your ac to stop putting out hot air if its randomly not opening up. Unfortunately, I think the valve is hard to see and get at- you might need to remove the cowl. Good luck.
The heat works awesome while the car is moving. This leads me to believe it isnt anything to do with the mechanical parts of the heating.


I am planning to do a flush to make sure I do not have a partial blockage in the cooling system. That is all I can guess at this point. My thoughts are that if it has a partial clog in the system its allowing the coolant to flow while the car is at a higher RPM, which allows hot coolant into the heater core giving me heat. When the car is at idle, coolant cannot flow freely and is causing back pressure. This resulting in coolant being forced into the overflow tank and air getting into the system. If this is not the problem.... I can only assume the head gasket it blown on the exhaust side allowing exhaust to enter the cooling system but little to no coolant into the exhaust.
 

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No harm in checking the heater valve while at park which is when you said you are experiencing no heat. A faulty valve could cause this problem. It should open and close fully as you turn the knob from full heat and full cold. If it only open/close partially then that could also be a problem. Good luck. Eliminating this will help in your troubleshooting.
 

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I would stop by my friendly radiator shop and have them test for exhaust gases in the coolant. Sounds like a blown head gasket to me.

Good luck!

Rky
 

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They should also be able to pressurize the cooling system using a pump on the cap and then look/listen for leaks.
 

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Seems to me like something may be restricting the flow, forcing coolant to find somewhere else to go and it's ended up in the overflow.

Are you getting any issues with the engine temp or is the only symptom the cabin heater?
 

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Discussion Starter #9
No harm in checking the heater valve while at park which is when you said you are experiencing no heat. A faulty valve could cause this problem. It should open and close fully as you turn the knob from full heat and full cold. If it only open/close partially then that could also be a problem. Good luck. Eliminating this will help in your troubleshooting.
I will still check this because you never know... but the car does not have to be in park for it to blow cool air. It will do it while sitting in traffic if you do not get the rpm's up.

Seems to me like something may be restricting the flow, forcing coolant to find somewhere else to go and it's ended up in the overflow.

Are you getting any issues with the engine temp or is the only symptom the cabin heater?
No other issues. The engine temp is always a little below the mid point of the gauge. Only things going on is the water sound when you take off (coolant being forced into the heater core where the air pocket is), Cold air when the car is not in motion and the coolant being forced into the overflow.

Thanks for all the input. I will keep you all posted if I find out more.
 

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sounds like water pump issue to me. could be a thermostat going bad too. If its none of them then id check the water supply line to the heater core for clogs.
 

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Hello everyone. I have been researching about my heat issues and have not gotten much help. I have an 03 Murano that recently started sounding like water would rush under the passenger side floor board when I would take off from a stop and the heat would get cold when I was at idle for a period of time. I searched and found that I probably had an air pocket in the system. I burped the system and all was perfect for a few weeks. Then I noticed the sound again and the loss of heat. I went thru the motions of burping the system again and all was fine for a few days and now I have air in the system again. I noticed that my overflow tank was filling up after each time I had this issue. I replaced the radiator cap and burped the system again. A few days later I have air in the system again... I do not have the typical blown head gasket issues. No coolant in the oil, exhaust is not steaming any more than normal in cold weather, only adding coolant to the radiator because its being pushed into the overflow tank which creates an air pocket at the heater core so when the car cools down it doesnt have room for the overflow tank to return the coolant due to the radiator appearing full. Can anyone give me suggestions??? I am at a total loss on this one. Never had issues like this with any other car I have ever owned.



Did you ever get this issue fixed
 
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