Land Rover Repair: overheating, coolant line, temperature guage

Question
-Are there any other sensors that detect heat or cause the temperature guage to red line, could the oxygen sensor (if bad) also indicate overheating? Again, thank you for your response. Susan------------------------
Followup To
Question -
In a recent correspondence you replied to which was deleted by my daughter by accident, I was wondering if you would be so kind enough to resend your response to: overheating landrover discovery automatic 1996, replaced radiator, visciuos fan clutch, thermostat, gear box, hoses and still vehicle is overheating. You suggested that it could be a heat sensor, but the message was erased before I could copy down the part. Please help me out as I am at my wits end and I love this vehicle and want to get it running right.
Answer -
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it could be a temperature sensor fault. Its possible that air is trapped somewhere in the system but after all you have done, I'd start to look at the sensors, specifically the temperature sensor switch.  The radiator hose connects to the thermostat housing and between the two is a temperature switch.  There are wires attached to this switch located on the outlet elbow (for thermostat).

Other owners have complained about the gearbox overheating and thus causing the engine to overheat.

An engine coolant line flush can be performed at most local garages. There is a kit that can be adapted and installed on your Disco. Every two years, you would then attach a garden hose and perform your own rad and coolant flush. Takes out any gunk and deposits that can lead to rad problems and overheating. Worth the $50 or so for peace of mind.

LR can perform a pressurized flush that cleans out any blockage that you may have.

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Hello Susan and Susan's father,

I will be glad to help a fellow Disco owner.  I'll track down the comments and send them to you as a followup message.

Let me know if you need more help.

Regards,

JohnMc  

Answer
Susan,

there are other temperature sensors on the Disco: the MAF (mass air flow) has a temp.sensor that monitors the temp of the air entering the engine.  If too hot or faulty, usually the ecu will be trip an error and you'd see a service engine light.

I believe there is a gearbox temperature sensor and this too would trip an error message.

The o2 sensors are use to high temps. In fact, they have a built-in means of heating themselves in order to function better.  There sole purpose is to measure the difference between the exhaust oxygen and the 'outside' oxygen.  The ECU monitors this voltage/equation and if a fault is detected, again a check engine light would be triggered.

I your case, either you have a plugged rad, air lock, engine blockage, faulty temperature sensor (found before the thermostat), faulty thermostat or (gulp) a random electrical failure that inhibits the ECM (Mr.Brain!) from detecting an error from one of the sensors.

Then there is the Automatic Temperature Control system.

A signal is supplied to the ECM whenever the ATC system requires the compressor clutch and/or condenser fans to function. The ECM integrates the control of these components with the engine management system. This ensures effective engine preparation for any sudden increase in the engine load.

The ECM will turn off the ATC compressor clutch if the engine coolant temperature exceeds 124°C (255°F). The ECM will turn on the condenser fans if the engine coolant temperature exceeds 100°C (212°F). See section on ATC for more details on the exact operation of the compressor clutch and condenser fans.

The ECM will store engine speed, battery voltage and engine load details whenever it detects a fault originating from the ATC circuit. It will store engine speed, intake air temperature and details of the battery voltage if the fault relates to the compressor clutch or condenser fan operation.

LR dealers have a 'testbook' diagnostic reader that can read this information.

Perhaps your problem is not with detection but with prevention?  Do you have a functioning viscous fan?  Do you hear the fan working in its attempt to cool down the engine?

Let me know,

Best of luck,

JohnMc