Running cold and O2 sensors - Defender Source
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  #1  
Old April 16th, 2015, 12:10 PM
WG_moots
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Wilmer
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Running cold and O2 sensors

Since I got my 95 SW, I noticed the temperature gauge only reached the . I ordered a new thermostat from the LR dealership 2miles down the road from my house (convenient). Last weekend I changed it out and found this. Old thermostat on right, new on on left:



It had a thermostat stamped 82, which is of course lower than the 88C temperature rating that the car should be running. I thought the new thermostat would do the trick but after a few days of driving the temperature gauge still only reaches about of the way up.

Any ideas what could be causing me to run cold? Maybe its the gauge? Ill look into getting a scan-gauge to get a second reading on the water temperature.

On another topic: My CEL came on a few days after buying the truck. The on-board display showed error code 44, which is the left side O2 sensor. I got two new O2 sensors from Rovers North and replaced both. I did the reset procedure and also had the battery disconnected (got a new Optima Yellow top) after changing out the O2 sensors. The light went off for a little (1 short drive) but has come back on and the is showing the same error code: 44.

Any ideas on this one?

Thanks!
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  #2  
Old April 16th, 2015, 12:28 PM
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leastonce
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Jason England
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First ... measure the actual engine temp .. best way is a Rover Gauge .. these trucks are pre-ODB II so need a custom reader ... fortunately the software is free!.. second best is a laser temp reader. Your gauge could be off. If it is reading badly a common upgrade is a VDO vison gauge and sensor as the LR genuine sensors are rubbish.

There are two temp sensors on the engine. One for the gauge and one for the ECU ( called coolant temp sensor). The ECU reading is important as that's the one the ECU uses to control fueling. This is the one the Rover Gauge reads.


Second get a proper correct thermostat. That 82C will make your engine run cold and suck gas - as the ECU will add extra fuel to bring it up to proper operating temp.

The thermostats job is to bring your engine up to temp ...

Look for exhaust air leaks on the side where you get bad 02 sensor readings ..
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Old April 16th, 2015, 02:07 PM
WG_moots
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Wilmer
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Thanks for the tips. I changed the thermostat to the correct one and it already looks like I am getting better gas mileage on this tank. My concern was that the gauge still showed the engine running cooler than optimal … even after the thermostat swap.

I planned on getting the “scan gauge” pretty soon anyway.

The exhaust is new, won't surprise me too much if it does have a leak.
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  #4  
Old April 16th, 2015, 02:19 PM
MotoMando
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Armando Centeno
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My mechanic swapped my thermostat from a 180 deg to a 160 deg. He said it would help keep the cabin cooler in the Summer. Could that be a reason my gas mileage sucks? Sorry for the hijack.
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Old April 16th, 2015, 02:36 PM
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leastonce
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Jason England
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Quote:
Originally Posted by MotoMando View Post
My mechanic swapped my thermostat from a 180 deg to a 160 deg. He said it would help keep the cabin cooler in the Summer. Could that be a reason my gas mileage sucks? Sorry for the hijack.
your gas mileage and your mechanic suck.... pretty stupid advice.
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  #6  
Old April 16th, 2015, 02:44 PM
MotoMando
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Armando Centeno
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Well, that's paraphrasing what he told me. All I heard was blah, blah, blah might make the cabin cooler. All I heard was "cooler cabin". Sold! I'm an easy sell. I'm getting 12.7 MPG for my daily commute (constant speed one way and stop and go the other way). Yesterday at highway speeds averaging 70 miles/hr, I averaged 11.4 MPG.
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Old April 16th, 2015, 03:07 PM
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John B.
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That is some scary mileage numbers.

You mechanic is a moron.

If your heater is leaking hot air into the cabin, fix the heater.
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Old April 16th, 2015, 04:12 PM
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leastonce
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Jason England
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Quote:
Originally Posted by Red90 View Post
That is some scary mileage numbers.

You mechanic is a moron.

If your heater is leaking hot air into the cabin, fix the heater.
Actually those mileage numbers aren't that bad for a NAS v8 ... you should be able to get a little better running at the right temp.

I'm generally around 13mpg although did manage an amazing 17.8mpg recently ... but that was following Jimmy and having set my ignition up on 'Briggs' Snap-on oscilloscope.
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