disco 300tdi into defender.. temp gauge query !!

Hey folks.

I've just upgraded my rad to a 4 core and installed a new inter cooler, replaced the thermostat and renewed all the piping.. now then!!

Previously my gauge would read half way up the white marked area when running around.. all day long, until towing, then it would shoot up to near in the red or in the red even though i had 2 electric fans on it. This set me on the route of the rad which was found to be like cardboard and knackered, which led me to the inter cooler which under a pressure test in water, was leaking badly in 3 places... so all upgraded and renewed.

Imagine my surprise then to start her up, bleed her system of every buble of air i can, take her up the road and find she now wants to sit right in the top of the white, or in black on temp gauge and still trying to sneak into red although fans do just hold it off

When i changed the thermostat i found this :



a large chunk of something jammed into it.

I have also now changed the sender sensor again to be sure.. and getting the same. This is https://www.steveparkers.com/produc...r-discovery-300-tdi-in-land-rover-90-and-110/

So.. finally my questions are..

Is it normal to actually be running at temp gauge in top of white / black ?? as have been running half way through the white for about 3yrs !!

Is it the case that i have to change something such as the gauge itself when you do this 300tdi disco engine into what was a 2.5 TD, G Reg ?? and if so..which one ?

Do i need a different, specific type of sensor to sync things if the reading i'm getting is incorrect ?? and if so how do i find the right one ??

I do have an electronic point and read thermometer.. and am getting in the early 90s at the thermostat housing.. mid to late 80's at the top hose and as little as late 60's to mid 70's at bottom hose.. all when in high black / low red on gauge. But this was once home having been towing with horse trailer and fans running.

Any suggestions folks !!!

just so you know.. this is the style of temp gauge i have:

Land Rover Defender Temperature gauge dash clock | eBay

Anyone have any ideas on this or have i finally hit a unique, not happened before problem.

mine never moves off the bottom of the gauge unless its sat ticking over for half an hour in traffic on a hot day. i have gone to the trouble of sourcing a new thermostat but having hit the BUY button lol, i'll get round to it one day though

round local under none towing isn't a big issue for me as is, but now i'm towing a horse trailer a few times a week.. that's a big problem as it's running the temp up much more. Hence my need to have a good gauge i can rely on... and hence the need for the thread and hope that someone has solved a similar issue.