Transmission oil temperature warning light

Recently the transmission oil temperature light on my v8 auto, comes on after even short journeys the vehicle is a 1995 disco.

I have checked that the pipes to the oil cooler (which is what I think the the small cylinder rad in front of the main radiator is) are getting hot (they appear to be) and I will check that the rad itself is getting warm (I assume it should).

I can't find any instructions in Haynes or RAVE to access the temperature sensor or in fact anything to do with this cooling system. The gearbox has recently had its fluids replaced and the levels on the dip stick look fine (maybe even a bit overfull) and the fluid is clean.

Couple of questions
1) I assume if the transmission is overheating ultimately it will seize up so ignoring the light is not an option?
2) What else should I be checking? If the sensor is faulty, I'm not even clear how I would gain access and replace it.
3) Anybody know a auto box specialist in NE Hants/Surry/Berks that they would recommend? Just in case I need to get it sorted

check level with engine running and gearbox in neutral top up through dipstick ,if worried about box drop a capful out and check colour and for metal sheen or particles ,if blackish or smells burnt ,clutch packs failing ,sensor usually on cooler pipes

jamesmartin said:

check level with engine running and gearbox in neutral top up through dipstick ,if worried about box drop a capful out and check colour and for metal sheen or particles ,if blackish or smells burnt ,clutch packs failing ,sensor usually on cooler pipes

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Thanks for the post; yep checked level and that's fine.

The fluid is clear red (it's almost transparent on the dipstick) with no signs of burn or particles.

Just a thought, would overheating be a symptom of incorrect transmission fluid being used?

I'll see what I can find on the cooler pipes to see if there is anything that looks like a sensor (i.e. with a couple of wires coming out of it )

The fluid cooler certainly gets warm in use, so there seems to be a flow through (one end cooler than the other)...

will get hot ,until locked at around 50 mph not all of power going into torque convertor is coming out to the wheels hence the feeling of slip in drive ,drive is by turbine or rotor been turned by pressure of oil like a wind turbine but with pressurised oil ,the power that isnt transmiutted becomes heat which is lost through oil cooler along with heat thats generated through the movement of gears through oil,sensor will have wires ,to check oil condition you need to drain a little ,but not when hot ,as you wont get plug back in ,atf or dextron 2 or 3 will be fine

Snifflebag said:

Thanks for the post; yep checked level and that's fine.

The fluid is clear red (it's almost transparent on the dipstick) with no signs of burn or particles.

Just a thought, would overheating be a symptom of incorrect transmission fluid being used?

I'll see what I can find on the cooler pipes to see if there is anything that looks like a sensor (i.e. with a couple of wires coming out of it )

The fluid cooler certainly gets warm in use, so there seems to be a flow through (one end cooler than the other)...

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it should be the same temp. if one is warmer than the other it may be blocked

jamesmartin said:

will get hot ,until locked at around 50 mph not all of power going into torque convertor is coming out to the wheels hence the feeling of slip in drive ... the power that isnt transmiutted becomes heat which is lost through oil cooler along with heat thats generated through the movement of gears through oil

Click to expand...

So for a "proper" test, I need to go for a faster run? If I've read your comments right, until around 50mph, the fluid is clearing excess heat from the torque convertor rather than from the gears?

defcrazy said:

it should be the same temp. if one is warmer than the other it may be blocked

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Mmmm, looks like I need to check that as well then. I assume this system is subject to airlocks if not refilled properly?

I am very suspicious of the sensor - the fact it is on solidly even when starting from cold just seems odd.

I'll do a test drive and also see if I can locate this sensor.

there will be no problems with air locks ,oil is pumped round ,only needs to be correct level,it is more likely switch or short in wiring unless you can feel fault developing in box

you could remove wires from switch and see if it still comes on it would indicate short in wiring,i believe switch is around the bottom of rad on coller pipes passenger side

Went out on Sunday evening and the light was on when cold and then went out as the engine warmed up. Looks like an electrical fault. I'll take a look for the sensor at the weekend and take some pictures when I find it. Thanks for the pointer as to where to look!

Will post an update once I've investigated further.