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2004 AWD Nissan Murano SE
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Discussion Starter #1
Ok, so I have a 2004 nissan murano I bought used. When I bought it, it overheated only when driving on the freeway. Went through the entire system with the car lot I bought it from. New water pump, new radiator, new thermostat x3, we even put a refurbished engine with lower miles into it, flushed the coolant system several times until it finally was discovered there was a hole in one of the tubes causing air in the coolant system. Has been driving great for months after that but still no heater, it blows air, just cold air. recently it has started to overheat only when i’m in drive thru’s. the moment I start driving again the temp gauge goes back down but it has started overheating everytime i’m stopped for longer than 5 minutes. any ideas what this could be?
 

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Probably trapped air, bleed your cooling system. Use this funnel which elevates the water level above the engine cooling system. Air will seek this higher level, and your cooling system will be burped of any air pockets that can cause the symptoms you mentioned...

Amazon.com: Lisle 24680 Spill-Free Funnel: Automotive
 

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2004 AWD Nissan Murano SE
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Discussion Starter #3

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2003 Nissan Murano SE AWD
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It's entirely possible that the previous owner of your MO bypassed the heater core due to a leak. Someone here is currently having their mechanic do the same thing...they're probably in a warm climate where heat isn't really needed. You or your mechanic might want to check to see if the hoses that run to/from the heater core are still intact, and if so are they hot with flowing coolant. Just out of curiosity, are you getting blowing air out of every part of the system, such as windshield defrost, dash upper vents and leg lower ducts? It's possible your temp control system isn't working correctly and isn't recognizing that you've selected heat and a hot temperature? Maybe it's stuck in "blow" mode and is just pushing normal air through the system. Not sure if there's a fuse or relay for that that could be checked.

As for your car overheating... My first thought since it's happening when MO is stopped for a prolonged period is, your radiator fans aren't kicking on. Some have said they only come on with the A/C, but I know they will come on if things become too hot...it will trigger at least one fan to engage. Maybe your fans aren't working. Check the fuses to be sure. If they're okay, have your fans tested for proper functioning. One of my fans quit working two years ago, so I I bought a new fan assembly via Amazon and it works great.
 

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2011 Nissan Murano LE AWD
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just tried that, and got nothing. i’m really at a loss here honestly.
Overheating while stopped along with no heat when the heater is turned on is symptomatic of air in the cooling system. I know you say you've tried bleeding the system already, but these cars can be notoriously hard to bleed.

I would suggest trying again with the lisle funnel and do it for an extended period. Make sure that you have the heat on the highest temperature setting (blower fan on low with A/C off) and that the cooling fans cycle on/off for at least a half dozen times. If you have a scan tool that can read live data, monitor coolant temperature while bleeding the system (...cooling fans should turn on low speed at about 203 F). You should start feeling heat coming out of the vents as the coolant temperature rises. If you don't then raise the engine speed to 3,000 RPMs to push out any air bubbles that may be stuck in the heater core until you start to feel heat.

If you do all that and you still don't get any heat from the vents then you have to consider the possibility that you have a blockage in the heater core itself or that the air mix door in the blower assembly is not actually switching from cold air to hot air.

EDIT: Cryogenix1 and I posted at the same time. Previous owner bypassing the heater core is another possibility. And, you can test that the IPDM can activate the fans on both low and high by running the Auto Active Test in this PDF attachment.
 

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2003 Nissan Murano SE AWD
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When I first developed a pinhole leak in my engine block, my temp gauge would fluctuate like crazy from a normal needle position to suddenly being all the way to H. I would assume it's due to air passing through the system and producing a bad reading. So, my question to you is, are you seeing any wild needle swings/changes with your temp gauge? I must've gotten lucky with my 2003 MO, because after I used some liquid aluminum to seal the pinhole leak, and then topped off the coolant, everything worked fine, so I guess the air worked its way out of the system fairly quickly, as it's supposed to.

If you're using concentrated coolant that requires dilution, be sure you're not over-diluting it, as doing so will create a lot of steam in the system which could cause poor-to-no coolant flow at times. It's also a good way to blow a hose.
 

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2004 AWD Nissan Murano SE
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Discussion Starter #7
It's entirely possible that the previous owner of your MO bypassed the heater core due to a leak. Someone here is currently having their mechanic do the same thing...they're probably in a warm climate where heat isn't really needed. You or your mechanic might want to check to see if the hoses that run to/from the heater core are still intact, and if so are they hot with flowing coolant. Just out of curiosity, are you getting blowing air out of every part of the system, such as windshield defrost, dash upper vents and leg lower ducts? It's possible your temp control system isn't working correctly and isn't recognizing that you've selected heat and a hot temperature? Maybe it's stuck in "blow" mode and is just pushing normal air through the system. Not sure if there's a fuse or relay for that that could be checked.

As for your car overheating... My first thought since it's happening when MO is stopped for a prolonged period is, your radiator fans aren't kicking on. Some have said they only come on with the A/C, but I know they will come on if things become too hot...it will trigger at least one fan to engage. Maybe your fans aren't working. Check the fuses to be sure. If they're okay, have your fans tested for proper functioning. One of my fans quit working two years ago, so I I bought a new fan assembly via Amazon and it works great.
yes, it blows air out of every system. and if I rev it to 2000 rpms I can get it to blow hot. as for the hoses to the heater core, they get ‘warm’ but not hot at all. one of them was borderline cold.
 

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2004 AWD Nissan Murano SE
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Discussion Starter #8
Overheating while stopped along with no heat when the heater is turned on is symptomatic of air in the cooling system. I know you say you've tried bleeding the system already, but these cars can be notoriously hard to bleed.

I would suggest trying again with the lisle funnel and do it for an extended period. Make sure that you have the heat on the highest temperature setting (blower fan on low with A/C off) and that the cooling fans cycle on/off for at least a half dozen times. If you have a scan tool that can read live data, monitor coolant temperature while bleeding the system (...cooling fans should turn on low speed at about 203 F). You should start feeling heat coming out of the vents as the coolant temperature rises. If you don't then raise the engine speed to 3,000 RPMs to push out any air bubbles that may be stuck in the heater core until you start to feel heat.

If you do all that and you still don't get any heat from the vents then you have to consider the possibility that you have a blockage in the heater core itself or that the air mix door in the blower assembly is not actually switching from cold air to hot air.

EDIT: Cryogenix1 and I posted at the same time. Previous owner bypassing the heater core is another possibility. And, you can test that the IPDM can activate the fans on both low and high by running the Auto Active Test in this PDF attachment.
I am considering taking it into the dealership and having them do it there.
 

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2011 Nissan Murano LE AWD
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yes, it blows air out of every system. and if I rev it to 2000 rpms I can get it to blow hot. as for the hoses to the heater core, they get ‘warm’ but not hot at all. one of them was borderline cold.
If you can get hot air to blow out the vents by revving the engine then there's definitely air getting stuck in the heater core and raising engine speed is just pushing it out to allow hot coolant to come in. If you have that Lisle funnel, try bleeding it again.
 
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