Td5 Defender Running Cold

D90 Td5 · Jun 30, 2020

Hi everyone,
I have a 2003 Defender 90 Td5 and have noticed that the temperature gauge isn't really rising that much. I did a 3-4 hour motorway drive and the needle was about 1/3 of the way up, but in 20-30 minute drives where speeds are about 30mph, the gauge is still in the blue. I noticed that when I drive at about 55mph the needle begins to rise into the normal area. Also, I do tend to drive with a fairly light right foot so I'm not really spooling the turbo much.
So my question is, is this normal for a td5? Is my driving style affecting the engine temp? Or is something wrong, e.g the thermostat stuck open?
Many thanks, Ollie

Scooby22 · Jul 1, 2020

TD5's do tend to run on the cool side, mine never gets more than about 1/3rd of the way and I have no viscous fan on, I put a new thermostat on mine and it still runs at the same temperature. Even driven hard on duel-carriageways on longer trips in never gets near half way.

bankz5152 · Jul 1, 2020

The gauges are terrible.

Some run at 1/3rd some at 1/2 some at 2/3rds. Long as its not zero or red its fine.

The gauge isnt actually giving you a temp its just giving a vague indication of the temp the ECU is seeing.

JimS · Jul 1, 2020

I think they tend towards the cooler side unless they are towing or going up mountains in Africa
I suppose this is the trade off making a vehicle for sale in climates all around the world

D90 Td5 · Jul 2, 2020

Hi everyone, thanks for the replies.
I've been testing things to try and sort the cold running, but to no avail. I've checked the coolant system for air locks, cleaned the electrical connector on the coolant temp sensor and made sure I used the turbo a bit more when driving, e.g a bit more throttle. The gauge will begin to creep into the normal range on the gauge at about 50mph, but not very high and not if I'm going much slower than this.
I also checked the temperature of the coolant pipes today after a 25-30min drive and the temperatures were only about 60 - 70 degrees, which seems too cold, and the block was only about 75 degrees.
I'm guessing it seems like I need a new thermostat, but I may be wrong. Does anyone agree with this, or should I not be worried?
Many thanks, Ollie

Scooby22 · Jul 2, 2020

They are cheap enough and easy to replace, but I would not worry about it, time to start worrying is when it gets too hot.

lightning · Jul 2, 2020

I’ve owned four Defender TD5’s, one was bought new.
All have been exactly the same....temperature gauge rises to just under half and stays there whatever the weather or driving style.
Obviously in Winter it takes longer to get to just under half, but on all four Defenders it did get there.

D90 Td5 · Nov 16, 2021

Hi everyone.
Sorry to revive an old thread but it occurred to me that I never followed up with how I solved this. In the end I bought a new genuine LR thermostat and now the needle sits happily at about half way in the normal region and the heater is warmer than it was before.
One check I did to see if it was the thermostat, and not just the gauge or temperature sensor, was to measure the temperature of the hoses using an infrared thermometer. It was a while ago now but I'm pretty sure the measured temperatures were around 60 or 70 degrees, which is less than the usual 90 or so degrees that I think is correct. I'm not sure if this is a proper way of checking this, but it makes sense to me.
Thanks

bluedog333 · Nov 16, 2021

D90 Td5 said:
Hi everyone.
Sorry to revive an old thread but it occurred to me that I never followed up with how I solved this. In the end I bought a new genuine LR thermostat and now the needle sits happily at about half way in the normal region and the heater is warmer than it was before.
One check I did to see if it was the thermostat, and not just the gauge or temperature sensor, was to measure the temperature of the hoses using an infrared thermometer. It was a while ago now but I'm pretty sure the measured temperatures were around 60 or 70 degrees, which is less than the usual 90 or so degrees that I think is correct. I'm not sure if this is a proper way of checking this, but it makes sense to me.
Thanks

I checked my coolant temp using a infra red thermometer on the hose and thermostat body. Thermometer measured 79*, new gauge showed 80*. Only way to know for sure would be to use a tube thermometer and dip it in the rad when up to temp. Infra red will give a good enough indication though.

neilly · Nov 16, 2021

D90 Td5 said:
using an infrared thermometer.

Be careful using an IR thermometer, You may know this, but just in case.

They measure from a cone in front of the lens, this cone gets big very quickly, so you really need to be close to get an accurate reading, also they suffer from emissivity issues, so different gloss levels / reflections on different materials / surface finishes cause inaccurate measurements.

They are great for comaprisons once you have verified the measurement using a touch probe.

Cheers

Td5 Defender Running Cold

D90 Td5

Member

Scooby22

Well-Known Member

bankz5152

Well-Known Member

JimS

Well-Known Member

D90 Td5

Member

Scooby22

Well-Known Member

lightning

Well-Known Member

D90 Td5

Member

bluedog333

Well-Known Member

neilly

Well-Known Member

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