My LR3 is a slight coolant leak that appears under the left front tire and in the wheel well. I have searched and searched, but can't seem to locate the leak. I believe (not confirmed) that the tank cap starts to leak when I am driving at normal speeds 40 mph and above and not when I am sitting. The temperature gauge does not move above half way (which I am not convinced is working properly). There is no abnormal noises coming from the heater. What I have noticed is that while sitting, the heater starts to blow cold air until I step on the gas pedal. When I initially start the truck, you can hear water gurgling on the passenger side. Any ideas or suggestions.

 

I think you may have a lack of coolant and hence an air lock somewhere in the system. It is the gurgling sound that suggests that. Also if you have a rear heater, set it on high and put your windows down in an attempt to get water circulating.

For some reason, (well too many hoses and water channels), the cooling system has great difficulty working air out by itself.

Have you done anything cooling system related recently such as change a thermostat or replace a hose?

Regardless, there is an air bleeder tee fitting under the black plastic engine cover. The plastic bleeder tee is shown in the diagram with the attached link. You might try messing with it with the engine idling and see if you can get some air to bleed out. It can be an all day job - very tedious.

Also the Jag engine uses what I call special antifreeze because of the aluminum bits within so do not refill with just any fluid that calls itself coolant.

DISCO3.CO.UK Photo Gallery - LR3 miscellaneous/LR3 Sparkle Silver 10 spoke Wheel Cromodora of Italy 18 inch x 8 ALY72190U

The aluminum engine does not like to be overheated and will overheat your wallet instead. Also the temperature gauge is a combo transmission oil/engine oil and coolant temp gauge and perhaps does a less than perfect job when it matters. In other words it is probably working OK but does not necessarily show either high oil temperature or high water temperature when it matters.

Below relates to the heater / AC system, files within that relate to the cooling system.

DISCO3.CO.UK Photo Gallery - Heater Air Conditioner System

 

I did not do anything except add antifreeze to the system when the low coolant message appeared. Since then, I drained and cleaned the system then refilled and attempted to bleed the system.

 

See this section of the shop manual. You can access and download thew whole thing for free in my signature. Air in cooling system will make the noises, plus provide a pocket where coolant sensor can be sampling air rather than hot coolant. As for gauge, an OBDII connected scanner that can read live data, like an Ultra Gauge, will give you more exact coolant temp readings.

https://www.cubby.com/pl/LR3+worksho...ooling-%204.4L