# Overheating issue



## MaddiMarie (Aug 12, 2021)

My 07 murano is overheating, even whilst idling. The radiator, water pump, thermostat and all hoses have been replaced as well as the overflow reservoir. What the heck could it possibly be so my only means of transportation is reliable again?? Help!!


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## rogoman (Dec 16, 2004)

There may be air pockets in the coolant system. Leave the radiator cap off; you'll have to drain some coolant to lower the coolant level first so that the coolant will not overflow from the filler neck of the radiator when it starts to warm up. Jack the front of your car up to help bleed the air from the cooling system. This puts your radiator higher than the rest of the cooling system and helps to bleed out the air pockets. Start your engine, and let it run until the system bleeds out air. It may take between 15 and 20 minutes for the engine to heat to the proper temperature and begin cycling coolant through. You'll observe the coolant level drop as the air is cycled out, and see air bubbles escaping from the radiator, and perhaps hear it gurgle; gradually add a little coolant at a time.

Observe the temperature gauge as this is happening. The gauge should decrease to normal or close to normal. This process helps the radiator feed the coolant more evenly, helping the system cool the engine like it's supposed to. It's no longer circulating air in your radiator instead of coolant.

After the system has cooled down, completely refill the radiator and the coolant reservoir again. The radiator may have been as much as half empty since earlier; it was simply air that made it seem full.


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## smj999smj (Jan 1, 2006)

Are the cooling fans working?


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## MaddiMarie (Aug 12, 2021)

As far as I know yes the fans are working but I will double check.


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## MaddiMarie (Aug 12, 2021)

The air has been bled out, that's why I'm baffled. Will try it again though, thank you.


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## rogoman (Dec 16, 2004)

MaddiMarie said:


> The air has been bled out, that's why I'm baffled. Will try it again though, thank you.





MaddiMarie said:


> My 07 murano is overheating, even whilst idling. The radiator, water pump, thermostat and all hoses have been replaced as well as the overflow reservoir. What the heck could it possibly be so my only means of transportation is reliable again?? Help!!


It looks like you've just about replaced everything in the cooling system. Did you replace the old thermostat with a Nissan OEM thermostat; if you replaced it with an aftermarket type like a Stant for instance, then you might run into overheating problems.

Run a pressure test on the cooling system. The gauge is normally pumped up to around 15 psi; at this point the system should hold that pressure for around 30 min or so. If it drops off rapidly in about one min or so, then there may be a *head gasket breach* which can be followed up with a compression test on all cylinders. If you find one or more weak cylinders, you can follow that up with a "leak-down" test to find out where you're losing compression. A blown head gasket can definitely cause engine overheating.


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