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CdnGriff

Member Since: 27 Jul 2025
Location: Ontario
Posts: 2

TD5 coolant/overheating

Hi, new owner, old TD5

1999 D90 in Canada, 250k km

Drove well for first week, then it suddenly lost power and temp gauge pegged into red. No warning.

Let it cool, got it home. Did it again.

Checked coolant, hoses, etc.

Now if I turn key, temp gauge immediately goes into red despite not being run in over a day.

Thermostat? Electrical fault?

Any help appreciated.

Total amateur and newbie.

27th Jul 2025 7:45pm

landy andy

Member Since: 15 Feb 2009
Location: Ware, Herts
Posts: 5982

2006 Defender 110 Td5 USW Zermatt Silver

Electrical fault. Check wiring underseat fuses, and check earth connections in same area. Even use a jump lead battery negative to underseat area, and, or bulkhead.

27th Jul 2025 8:27pm

jst

Member Since: 14 Jan 2008
Location: Taunton
Posts: 8341

2011 Defender 110 Puma 2.4 USW Stornoway Grey

Check battery earth strap. I would remove chassis end and clean up and refit. Cheers

James
110 2010 XS Utility
130 2011 M57 bespoke Camper
90 2010 Hardtop
90 M57 1988 Hardtop

27th Jul 2025 9:23pm

Penfold_6290

Member Since: 22 Sep 2021
Location: Dorset
Posts: 388

What they said plus it’s a good idea to run a ground cable from the casing of the ECU direct to the negative battery terminal. My temperature gauge would often ‘spike’ into the red momentarily and lose power. Never done it since I grounded the ECU casing. I’m saying grounded when I really want to say earthed, but I’m trying to speak a bit of Canadian.

27th Jul 2025 10:47pm

TexasRover

Member Since: 24 Nov 2022
Location: Paris
Posts: 1284

2002 Defender 110 Td5 DCPU Chawton White

Side note, but I believe grounding to be the more appropriate term especially since a car on rubber wheels has little connection to Earth. It's obviously the negative battery terminal that is connected to all all the other negatives (zero potential between them). According to AI both terms are not the most suitable

Earthing

Earthing refers to connecting a circuit directly to the ground.
It protects against electrical spikes and potential damage to life and property.
The wire used for earthing is typically green in color.

Grounding

Grounding means creating a zero potential in a circuit without a direct connection to the ground.
It provides insulation against accidental currents and helps prevent overloads.
The wire used for grounding is usually black in color.

28th Jul 2025 8:18am

CdnGriff

Member Since: 27 Jul 2025
Location: Ontario
Posts: 2

Thanks to all for the suggestions.

Trying to chase the electrical fault now. There are many many added on wires and bits in this thing.

I also may have the “oil in the ECU” problem, the wiring is pretty oily. Is that just an extra problem or is it possibly the fault?

Feel free to talk to me as one who needs things explained slowly and with crayons.

Cheers,

28th Jul 2025 11:56pm

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