Over heating

[Paul ward]

My Nissan navara d40 2007 Truck is blowing cold air when the heater is on hot and the engine temperature gauge is going up really high if the revs exceed 1000 and when I decrease under 1000 revs it goes down to normal again and as long as I am crawing under 1000 it stays in the normal postion but no warning lights have come on Any diagnostic help is welcomed. Thanks in advance.

 

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thermostat stuck open?? does system need flush

 

[KevinE]

My Nissan navara d40 2007 Truck is blowing cold air when the heater is on hot and the engine temperature gauge is going up really high if the revs exceed 1000 and when I decrease under 1000 revs it goes down to normal again and as long as I am crawing under 1000 it stays in the normal postion but no warning lights have come on Any diagnostic help is welcomed. Thanks in advance.

I'd say that you have a blockage somewhere if the heater isn't working, but the problem of the temp gauge going up & down with the revs sounds more like a temp switch issue than actual over heating?

Have you checked what temps the ECU is seeing with an OBD reader? I'm not familiar with the D40 system, but often there are 2 temp switches on the engine; a small one which sends a signal to the dash gauge & a larger one which sends a signal to the ECU. Just to confuse the issue, sometimes the manufacturer uses one switch to do both jobs. If the ECU is seeing high temps, the car "should" go into limp mode. So if your gauge is going up, but you're not going into limp mode, you may have a problem with a temp switch?

Anyway, testing the switch is easy if you have a multi meter & you can eliminate the switch as the problem if it's working OK. There are a few videos on Youtube on how to do it, I personally like this one; Temp Switch Test

I had a similar issue with a petrol V6 & replacing both temp switches fixed it.

Good luck!

 

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How to diagnose a Faulty Engine Coolant Temperature (ECT) Sensor - 2005 Pontiac G6
10 minuet job to test sensor with multimeter

 

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How to diagnose a Faulty Engine Coolant Temperature (ECT) Sensor - 2005 Pontiac G6
10 minuet job to test sensor with multimeter

when you remove sensor quickly plug opening no need to remove fluid

 

[KevinE]

There's no need to remove the sensor from the engine if you do it the way that is shown in the video I posted above. It's very quick & easy if you have a multi meter.

Replacing the sensors is extremely simple. Just unclip the wiring, remove the old one & insert the new one. They're self sealing.

IMPORTANT: make sure that the engine is stone cold when you replace the sensor or you will get burned by hot coolant when you remove the old sensor.