briefly.. car randomly thinks it is overheating and goes into limp-home. Turning ignition on and off resets the temperature gauge quicker than water can physically cool. Faulty sensor is therefore the most likely answer you would guess.

Unfortunately no error code logged and can't replicate the issue on demand (it's happened 3 times now, all in unrelated circumstances). LRA called out and took the car to Lookers Park Royal. Enterprise delivered a RRS TDV8 replacement, nice car but wood interior . That was actually a fairly decent service (came out Sunday PM, brought replacement car this morning albeit with zero fuel and a 'service needed' message on the dash).

Now a stalemate to get LR to agree to replace the sensor despite no codes being logged/fault not being replicated on demand. Photographic evidence supplied of MAX HIGH temperature gauge reading. This all being brokered via Lookers Park Royal. Car is off to the Alps in 3 weeks and if it breaks down there.....

Why can't Landrover ever display even a modicum of common sense??  ============
2010 TDV8 HSE - ooo laa laaaaaaaaa
2007 TDV8 HSE - superb car and very reliable
============
2012 - dearly departed, sadly missed.. to return in late 2013 with a new TDV8!

How much for a new sensor?? 

Supporting the London Air Ambulance with my Brothers

If anything like my first FL2 With a similar issue about a fiver plus fitting for the water sensor

rrsboy If your off to the Alps why not just pay for the sensor. Job done. You then have 2 weeks to drive about to see if fault happens again. 

Supporting the London Air Ambulance with my Brothers

principal plus at this rate I might just take their hire car.....  ============
2010 TDV8 HSE - ooo laa laaaaaaaaa
2007 TDV8 HSE - superb car and very reliable
============
2012 - dearly departed, sadly missed.. to return in late 2013 with a new TDV8!

£13 but it looks an arse to do and probably would take about 5hrs to rebleed the system Mike

2014 Facelift Discovery

car is back with me now, sensor wasn't changed but I'm told a wire & connector were found disconnected. They control the fan speed and could have caused the car to overheat. Separately, the temperature sensor may be 'damped' like the fuel level sensor is, explaining why turning the car off and back on could appear to show temperature returning to normal (or something like that).

Bobby - any diagrams to show this wire & connector? Do you know if the temperature reading is damped in the way explained?

thanks to Lookers PR for their speedy assistance. ============
2010 TDV8 HSE - ooo laa laaaaaaaaa
2007 TDV8 HSE - superb car and very reliable
============
2012 - dearly departed, sadly missed.. to return in late 2013 with a new TDV8!

The temperature of the cooling system is monitored by the ECM via the Engine Coolant temperature (ECT) sensor located in the coolant housing. The ECM uses signals from this sensor to control the cooling fan operation. (The same sensor in the previous post).

Regulation of the coolant temperature is achieved via engagement of the electro-viscous fan assembly. This is
controlled by a Pulse Width Modulated (PWM) signal with a duty cycle of between 0 and 100%, provided by the ECM and derived from inputs based on:


Coolant temperature

Ambient air temperature

Engine inlet air temperature

Air Conditioning (AC) system pressure

AC switch operation

Transmission oil temperature

Fan speed control is variable; however, because the fan is driven directly from the engine, the maximum fan speed available is tied to engine speed. At high engine speeds the fan is progressively disengaged to protect the clutch unit. This system provides very high levels of fan power, up to 5 kilo Watts (kW), with enhanced noise and fuel economy benefits compared to mechanically controlled viscous fans.

The speed of the cooling fan is also influenced by vehicle road speed. The ECM adjusts the speed of the cooling
fans, to compensate for the ram effect of vehicle speed, using the Controller Area Network (CAN) road speed signal received from the Anti-lock Braking System (ABS) module.

From your previous explanations, it would seem that the there is no actual over-heating - just the gauge receiving false information. That means all components, including the fan, are working well - so what wire and connector are we talking about? If the fan speed was not proper then there would have been an actual overheating! Malaysia Boleh!
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many thanks Bobby

"From your previous explanations, it would seem that the there is no actual over-heating - just the gauge receiving false information. That means all components, including the fan, are working well - so what wire and connector are we talking about? If the fan speed was not proper then there would have been an actual overheating!"

As i understand the explanation offered by LR, the wire that connects to the fan to control it's speed wasn't actually connected, so that it span just at a fixed speed. This would suggest the overheating was a genuine overheating but for one thing - turning ignition on and off reset the temperature gauge immediately. Normally this would imply the sensor was faulty (because water can't cool that much in the 1 second it takes to turn ignition on and off). However an alternative explanation could be that the temperature sensor reading is 'damped' in a similar way to the fuel level sensor (the process that stops the fuel reading moving dramatically as you go around a corner or up a hill).

do either of these things sound plausible to you?

many thanks ============
2010 TDV8 HSE - ooo laa laaaaaaaaa
2007 TDV8 HSE - superb car and very reliable
============
2012 - dearly departed, sadly missed.. to return in late 2013 with a new TDV8!

The Fuel Level Sensors [Magnetic Passive Position Sensor (MAPPS)] fitted to your vehicle are so advanced that it is practically impossible to be "damped".

It would be better if you get the ECT sensor replaced (very cheap) and monitor the situation first.  Malaysia Boleh!
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Larini Sports Exhaust, K&N Air Filter
______________________________
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thanks as always for the advice and info Bobby. To clarify when I say 'damped' I mean in the sense that as the fuel sloshes about the tank e.g. going up/down hill or around a corner at speed, the fuel guage doesn't move around wildly as you might expect (and as in car of 15 years ago). Somehow it filters out the big movements - this is what I term 'damping' but i'd love to hear how it actually manages it? ============
2010 TDV8 HSE - ooo laa laaaaaaaaa
2007 TDV8 HSE - superb car and very reliable
============
2012 - dearly departed, sadly missed.. to return in late 2013 with a new TDV8!

Sorry for misreading "damped".

This is a write-up on Fuel Level Sensors for MY2009 which I think will still apply to current years...

Fuel Level Sensors

The sensor is a Magnetic Passive Position Sensor (MAPPS) which provides a variable resistance to earth for the output from the fuel gauge. The sensor is sealed from the fuel preventing contamination of the contacts, increasing reliability. The front and rear fuel level sensors are connected to the external electrical connector on the flange via the connectors on the underside of the fuel pump module flange.

The front and rear sensors are attached to the front of the carrier and are accessible via the fuel pump flange aperture.

The sensor comprises a series of 51 film resistors mounted in an arc on a ceramic surface. The resistors are wired in series with individual contacts. A soft magnetic foil with 51 flexible contacts is mounted a small distance above the film resistors. A magnet, located below the ceramic surface, is attached to the sender unit float arm. As the float arm moves the magnet follows the same arc as the film resistors. The magnet pulls the flexible contacts onto the opposite film resistor contacts forming an electrical circuit.

Sensor Operating Principle



The film resistors are arranged in a linear arc with resistance ranging from 51.2 to 992.11 Ohms. The electrical output signal is output proportional to the amount of fuel in the tank and the position of the float arm. The measured resistance is processed by the instrument cluster to implement an anti-slosh function. This monitors the signal and updates the fuel gauge pointer position at regular intervals, preventing constant pointer movement caused by fuel movement in the tank due to cornering or braking.

A warning lamp is incorporated in the instrument cluster and illuminates when the fuel level is at or below 14 liters (3.69 US gallons).

The fuel level sender signal is converted into a CAN message by the instrument cluster as a direct interpretation of the fuel tank contents in liters.

Hope the above helps!  Malaysia Boleh!
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Larini Sports Exhaust, K&N Air Filter
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superb - that is very interesting!

this bit
"The measured resistance is processed by the instrument cluster to implement an anti-slosh function. This monitors the signal and updates the fuel gauge pointer position at regular intervals, preventing constant pointer movement caused by fuel movement in the tank due to cornering or braking."

do you think the same 'processing' happens with the signal from the engine temperature sensor i.e. the instrument cluster processes it in such a way as to avoid dramatic moves higher or lower? ============
2010 TDV8 HSE - ooo laa laaaaaaaaa
2007 TDV8 HSE - superb car and very reliable
============
2012 - dearly departed, sadly missed.. to return in late 2013 with a new TDV8!

No, it's different.

The ECM (engine control module) circuit for the ECT (engine coolant temperature) sensor consists of an internal voltage divider circuit which incorporates an NTC thermistor. As the coolant temperature rises the resistance through the sensor decreases and vice versa. The output from the sensor is the change in voltage as the thermistor allows more current to pass to earth relative to the temperature of the coolant.

The following symptoms may be because of ECT sensor failure:

Difficult cold start.
Difficult hot start.
Engine performance compromised.
Temperature gauge inoperative or inaccurate reading. Malaysia Boleh!
4.2SC Chawton White, Stormers
Tasmod's Sills, Wind Deflectors, LR Sills
Clear Side Repeaters, Towbar
Larini Sports Exhaust, K&N Air Filter
______________________________
WINNER - 2008 'Tech-Head Of The Year' Award
WINNER - 2009 Outstanding Contribution
WINNER - 2009 'Tech-Head Of The Year' Award

Bobby - does your 'bible' say anything about the fan continuing to run once the ignition is turned off? In cars of old this was a frequent occurrence, you'd park up and the fan would continue to run for a few minutes to keep cooling the hot engine. However I cannot get my fan to keep running no matter how arduous or long my journey has been? ============
2010 TDV8 HSE - ooo laa laaaaaaaaa
2007 TDV8 HSE - superb car and very reliable
============
2012 - dearly departed, sadly missed.. to return in late 2013 with a new TDV8!