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CdnGriff



Member Since: 27 Jul 2025
Location: Ontario
Posts: 4
Canada 1999 Defender 90 Td5 CSW Keswick Green
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.
Post #1072313 27th Jul 2025 7:45pm
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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.
Post #1072317 27th Jul 2025 8:27pm
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jst



Member Since: 14 Jan 2008
Location: Taunton
Posts: 8347
 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
Post #1072321 27th Jul 2025 9:23pm
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Penfold_6290



Member Since: 22 Sep 2021
Location: Dorset
Posts: 388
United Kingdom 2002 Defender 110 Td5 CSW Epsom Green
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.
Post #1072324 27th Jul 2025 10:47pm
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TexasRover



Member Since: 24 Nov 2022
Location: Paris
Posts: 1284
France 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.
Post #1072329 28th Jul 2025 8:18am
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CdnGriff



Member Since: 27 Jul 2025
Location: Ontario
Posts: 4
Canada 1999 Defender 90 Td5 CSW Keswick Green
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,
Post #1072399 28th Jul 2025 11:56pm
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CdnGriff



Member Since: 27 Jul 2025
Location: Ontario
Posts: 4
Canada 1999 Defender 90 Td5 CSW Keswick Green
Penfold_6290 wrote:
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.


I’ve cleaned up all the wiring, checked the earth strap, ran a jump lead from earth point in ECU box to the battery, still same fault.

Does the ECU “casing” mean the underseat cubby/box?

Willing to try anything at this point.
Post #1072496 30th Jul 2025 12:44pm
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4RF RDS



Member Since: 19 Jul 2015
Location: Ottawa
Posts: 983
Canada 2000 Defender 110 Td5 XS CSW Epsom Green
Where are you in Ontario? I am in Ottawa, happy to assist and we can scan with my Nanocom and see what’s up. Also suggest joining Ottawa Valley Land Rovers on FB (largest and oldest Land Rover club in North America). If you do join the FB group post this issue, lots of us here in Ontario with Td5s. I might be able to hook you up with someone nearby to assist you if you are not on FB.

Definitely clean up that oil in the red ECU plug use electrical cleaner or brake cleaner and dry it out. And change the injector harness. ECU casing being referring to is the silver box under the seat. Use one of the bolts securing it as a ground wire anchor. Feel free to PM me off line if that is easier…

Good luck 2010 Range Rover MkIII Autobiography Super Charged (Idris)
2003 Range Rover Mk III (Desmond FitzWilliam)
2000 Defender 110 CSW TD5 (CTX)
1992 Range Rover Classic (Lizzy)
1972 Series III 300 Tdi (Stanwood)
1967 MGB GT

Every normal man must be tempted at times to spit on his hands, hoist the black flag, and begin to slit throats.
H. L. Mencken (1880 - 1956)
Post #1072521 30th Jul 2025 4:03pm
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CdnGriff



Member Since: 27 Jul 2025
Location: Ontario
Posts: 4
Canada 1999 Defender 90 Td5 CSW Keswick Green
Thanks!

I’m in Kingston, so not very far, but far enough at this point.

I will look up the Ottawa group.

I did clean out the ECU and connector and will get on the harness swap; not sure that will fix current problem.

I will certainly reach out to you later.

Thanks again
Post #1072523 30th Jul 2025 4:21pm
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4RF RDS



Member Since: 19 Jul 2015
Location: Ottawa
Posts: 983
Canada 2000 Defender 110 Td5 XS CSW Epsom Green
That will not affect the overheating issue but needs attention for sure. Parts availability in Ontario for Td5 is great at 3Brothers Classic Land Rovers in Paris (near Hamilton). We have a several members in and around K-town. I’ll look in the club database to see if anyone has a Td5.

https://3brothersclassicrovers.com/

https://ovlr.ca/

Stay in touch.

Cheers 2010 Range Rover MkIII Autobiography Super Charged (Idris)
2003 Range Rover Mk III (Desmond FitzWilliam)
2000 Defender 110 CSW TD5 (CTX)
1992 Range Rover Classic (Lizzy)
1972 Series III 300 Tdi (Stanwood)
1967 MGB GT

Every normal man must be tempted at times to spit on his hands, hoist the black flag, and begin to slit throats.
H. L. Mencken (1880 - 1956)
Post #1072524 30th Jul 2025 4:32pm
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