Nanocom temp reading.

Morning,
I have noticed over the last few years that when towing or driving 'fast' when heavily loaded the temperature reading on my nanocom gradually climbs to the point where the screen goes red and warns me of imminent death and that. The temp guage on the dash remains in the middle. Thermostat opens at 90C as expected, engine is running well etc. Has anyone noticed a similar thing with their own nanocom/TD5? Is it just OCD? (got a spare waterpump under the seat...)
Cheers,
Mike.

Have you set the warning threshold too low? My classic Nanocom does not have this option and not sure if the later ones do.

The warning set point must be as the nanocom is delivered. Not sure I could find where to set it...
It does go off at 96C which is not that much above the 90C thermostat temp. I am just surprised that the temp goes up that much in the mild UK temperatures. I suppose its possible that the thermostat is not opening fully, but a good look around on the forums suggests that the TD5 is overcooled, just surprised that the temp steadily rises when full throttle is used for any extended period. Cheers,
Mike.

I would be looking for air flow problems at the front, it doesnt take much to get the temp up a degree or two.
When iI fitted an elec fan in front of my series rad I noticed the normal running temp climbed 2 degrees.
Both my tdi engines temps climb to mid 90 when pushed hard for some period of time, ie thrash down the motorway.
Dont forget the dash temp gauge is not linear.

The symptoms you describe are classic signs of "heat soak" which point to a marginal cooling system that works well at low engine speeds and loading but struggles when the engine is working hard. However what does the Nanocom show as max temperature under these conditions? My TD5 runs at about 96C according to my Nanocom Classic.I have a new radiator, pump, hoses, and heater matrix. You don't mention the expansion cap is venting so coolant pressure (increases with temperature) can not be that high. Does the heater feel excessively hot when the Nanocom alerts? Are the radiator hoses rock hard?

As Lynall says check the radiator fins are not bent or clogged. Check the viscous fan is actually working as it shoulkd "firm up" as the temperature rises. At idle from cold you should be able to stop and hold the fan from spinning but as the engine warms up it should become progressively harder to hold the fan. (Be very careful how you do this as it is very easy to injure yourself or the radiator) I use a leather welder's gauntlet to carefully slow and grab the fan blades. DO NOT rev the engine while holding the fan blades. If the fan does appear suspect then you can simply make the viscous unit a solid one with a couple of self tappers so the fan spins hot or cold. This is a standard mod in many parts of Africa along with additional electric fans fitted in front of the intercooler..

It may be your water pump is not as efficient as it could be. On the later pumps with pressed steel impellors they corrode away and the pump becomes lazy. The earlier cast impellor pumps are far superior and do not suffer with corrosion but they are few and far between. I would also flush the radiator core, heater matrix, and engine in both directions until the water runs clear. Before flushing put some kettle descaler in the cooling system and drive it until nice and hot. Drain and flush then refill with 50% mix of OAT antifreeze and water. Don't leave the descaler in there as it can corrode the aluminium engine parts over time. I've done this many times with no problems.

Thanks for the responses, highest temp seen is 97ish, I have replaced the expansion cap a few years ago as it was leaking a little, leak tight now with no loss of coolant. Did a system flush and new OAT at the same time, hoses go stiff when engine is hot but not rock hard. I was wondering about the pump impeller corroding, hence the spare... Haven't checked the fan yet (now on to do list) but I can confirm that the air con exchanger, the intercooler, and the rad itself are all clear.
Cheers, Mike.

I would take a good look at the hoses if they are going stiff, my td5 did this and it was the first signs of the head gasket going, it was the early engines with plastic head dowels and what happens is the engine constantly gets hot and the head starts to shuffle sideways allowing the valves to run down the side of the cylinder bore.
On my my td5 I ran it for 4 yrs and 50k after the head gasket done with no issues, I only ever heard the viscous come in a few times and that was after fitting a fatter intercooler which reduced the air flow slightly to the rad and when pushed hard up a big hill the viscous would come in.

Hmmm, I did assume that as it is a pressurised system the hoses would get stiffer when the engine is hot. Its a 2003 and think has the steel dowls. No sign of contamination in the oil or water (not losing either) and has been like this for a few years so I'm hoping its not HG related. More looking I think....
Cheers all.

Later engines not such an issue.

Well finally got around to giving this a a good coat of looking at. LR manual says thermostat fully open at 96 C the temp i have been seeing on my Nanocom. But my ocd wouldn't let me be so I drained and flushed the system and replaced the water pump and thermostat with OEM new ones.
I can now report that it made no difference...At least i am happy that neither are about to fail, its just gone past 100,000. Pic of old pump attached, no sign of wear...

Happy days. Your old pump looks good so hang on to it as a spare.