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Printerjohn

Member Since: 12 Mar 2024
Location: Poole Dorset
Posts: 23

2006 Defender 110 Td5 XS CSW Barolo Black

Engine hot, radiator cold?

After returning from France where we had overheating issues, and a garage said your engine is hot, but radiator is cold due to the thermostat sticking closed, and as they didn't have the correct thermostat the mechanic wedged the thermostat open, and we travelled home engine temperature with this done maxed out around 65 degrees C. I have this afternoon replaced the thermostat and top radiator hose with genuine Land Rover parts. The engine is now running between 80 and 100 degrees C, and the radiator is still cold except for the very top corner where the hose comes from the head. The pipe at the bottom of the thermostat is cold, and I can see the pink coolant in the bottom of the thermostat body. Any suggestions as to what is wrong to cause the thermostat not to open.

20th Nov 2024 5:58pm

landy andy

Member Since: 15 Feb 2009
Location: Ware, Herts
Posts: 5726

2006 Defender 110 Td5 USW Zermatt Silver

Are you sure you have an issue?

The engine will want to run at 80-100c, and if your temps are like here today getting the engine really hot is going to take some work. When it was running 65c it was running too cold.

20th Nov 2024 6:06pm

Printerjohn

Member Since: 12 Mar 2024
Location: Poole Dorset
Posts: 23

Should the thermostat not be opening at 89 degrees to allow the water to circulate through the radiator? There's upto 100 degrees at the top of the thermostat with top hoses all hot, but cold on the other side of the thermostat.

20th Nov 2024 6:09pm

landy andy

Member Since: 15 Feb 2009
Location: Ware, Herts
Posts: 5726

Yes it should open at 89, but it’s not going to take much for it to drop 10 degrees from the 100.

Where are you getting your temperatures from?

I’m not saying you have no problem, just that it probably needs a good run and test. Today here things barely got above 0 c, so doubt my radiator was doing anything.

Only other things I can think of is air lock, weak water pump, or blocked radiator. Possibly the air lock, but the others I think would show other symptoms.

20th Nov 2024 8:12pm

Printerjohn

Member Since: 12 Mar 2024
Location: Poole Dorset
Posts: 23

Temperature is coolant temperature readings on Nanocom. I will try a longer run tomorrow. The coolant looked nice and clean. Would the coolant be clean if there are blockages in the radiator?

20th Nov 2024 8:26pm

landy andy

Member Since: 15 Feb 2009
Location: Ware, Herts
Posts: 5726

So your temperature is taken from the cylinder head and at a max of 100c. The thermostat is a distance away and mounted in a pipe which is being effected by windchill. At the thermostat opens at 90c. So it only had to loose 10c during a cold day ????

I think the rest of your system is ok as was so different when thermostat stuck open

I’m just thinking it through with you, not that I know anything.

20th Nov 2024 8:52pm

Printerjohn

Member Since: 12 Mar 2024
Location: Poole Dorset
Posts: 23

Thanks, see what your saying, it should be warmer here in Dorset at the weekend (15 degrees) so will see how it goes then with a decent run.

20th Nov 2024 8:56pm

landy andy

Member Since: 15 Feb 2009
Location: Ware, Herts
Posts: 5726

I think a decent is best. They really don’t run hot, even after a good run the temps soon plummet once stationary. And it’s very rare that the fan kicks in. I just think that you can start to over study something once you’ve had a problem with it. I’m sure if it was a most people they would have taken it to a garage, had a new thermostat fitted, then been given the vehicle back, and never given it a second thought. Sometimes being a hands on LR owner can cause us anxiety.

20th Nov 2024 9:19pm

TexasRover

Member Since: 24 Nov 2022
Location: Paris
Posts: 1084

2002 Defender 110 Td5 DCPU Chawton White

Hi Landy Andy - your observations about temperature being on the cool side is the same I see - but after I fitted a new (LR $$) thermostat. I was thinking this was dt a faulty thermostat and was going to chance it out again.

I don't really like to see an engine run cold especially since I am not really doing a lot of long distance, kinda hoping in away it is a faulty thermostat, but admit probably unlikely then..

21st Nov 2024 1:15pm

mark1200

Member Since: 09 Oct 2011
Location: peterborough
Posts: 75

In my opinion the td5 is over cooled as it has to work in the hot desert as well as the arctic climates. this is why some of us struggle to get any decent heat from the heater matrix lol so on a cold winters day your thermostat probably wont open unless your towing up a steep hill ?
Like Andy says if the thermostat did open the rush of cold water would soon cool the engine and quickly close again and you probably would not notice ?
Question when you think your engine is hot have you tried to see how hot the air is coming from the heater ?

21st Nov 2024 3:51pm

Printerjohn

Member Since: 12 Mar 2024
Location: Poole Dorset
Posts: 23

I have had a chance to take her out for a longer run, and from the change in heating (running warm to cold) I can see that the thermostat is operating. The radiator is very hot in the top right hand corner when the thermostat closed, and then changes to warm when open. The radiator is just slightly off being cold. When I I returned home I did a sniff test, and after 3 minutes get a colour change to show head gasket is leaking, so preparing for a big job.

25th Nov 2024 2:47pm

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