Defender 300tdi temp gauge fault?

I have recently had a disaster with my defender and had to replace the engine.
As a result of this my temp gauge is reading faulty, I think.
When the ignition is off the needle sits at a low normal position. When the lead to the temp sender uint is earthed it returns to the bottom as normal . After running the engine the temp gauge rises and just about hits the red .After switching off the ignition again it falls to a low normal reading again.
I have changed the temp sensor and thermostat No joy.
Can anyone shed any light . The gauge was working perfectly before the engine killed itself ( failed oil pump).

poor earth

Heuer27
When the wire to the sensor ( in the thermostat housing ) is earthed , the guage should go full limit to the red.
Keep in mind that there are two types of sender unit for 300Tdi Defender , I don't know what the difference is , but one has a green plastic top and the other a black . Having the wrong one will make your guage do crazy things .Make sure the contact between the wire and the sensor is good and as always , check that all the earths are connected and clean . Your main areas to check earths is from the neg battery lead to the transfer case and one from your engine to the body .

Thanks guys, I've checked the earth to the sender and it hits the red as you described.
Its a green sender i fitted thats what was in the old one.
I got behind the dash and disconnected the gauge completely and it still read low normal. So i'm thinking its the gauge unless anyone can say different.
I've got a TD5 gauge will that fit right in. Looks different though i think its just the mounting.

Fitted new gauge and still overheated . Turned out the new thermostat was not opening and causing it to over heat . I didn't know the water pumps the wrong way from most other cars which caused a lot of stripping down and head scratching before working out what the problem was .Should it be an 88deg thermostat or 83deg seems you can fit both .

heuer27 said:

Fitted new gauge and still overheated . Turned out the new thermostat was not opening and causing it to over heat . I didn't know the water pumps the wrong way from most other cars which caused a lot of stripping down and head scratching before working out what the problem was .Should it be an 88deg thermostat or 83deg seems you can fit both .

Click to expand...

personnal choice

Im having this problem, i have a 300tdi in an ex v8 disco 2, the engine gave up and i replaced it but now my temp guage is over reading, i changed the sensor for the original one but still reads the same, checked the stat thats fine, any ideas?

You need the black sender not green. Green is Disco and will not talk to the defender gauge. I had the same problem recently. Broke sender off in housing and replaced with the green one. Wrong one. You get that!

Earth cable from neg on battery has a clip type thingamajig (located by gearbox crossmember ) I had the same problem on my old 300 clean it with wire brush an reattach to chassis the clip might even need a hit with a hammer to tighten it back on to the copper