Hello there,

I've read a lot before making a post about this popular topic, in my case I changed the coolant reservoir last year, and 2 months ago the Thermostat housing, I still get leaks. is it the radiator?

And yes, its still leaking, its less after changing the thermostat housing but I don't know what else to expect.

 

Jack it up, set it on stands, pull the air dam shroud off the bottom and bring the engine up to temp idling. Look at all of the connections around the auxiliary coolant pump. Inspect the plastic radiator side tanks. Check the two connections for the heater hose pipes where it transitions from rubber to aluminum near the reservoir tank. Take a flashlight and look down into the "V" of the top of the engine, underneath the intake manifold. Look underneath the water pump on the engine front cover. I've found leaks in all of those places on mine and I've pretty much replaced every part of the cooling system at this point and I'm still getting leaks. Rubber and plastic from 2004 or 2005 isn't going to be very reliable by now. If I buy one of these cars again I'm just going to replace the entire cooling system before I start driving it. ~800 dollars in parts one time would have saved me hours chasing little seeps.

 

I have a hard time seeing leaks with a hot engine.
Better to let everything cool off and use a coolant pressure tester to find it.

I have found the parts stores have this tool on their free loaner list but sometimes you have difficulty finding the correct adapter for your Jaguar.

As was posted above with the age of the car ALL plastic and rubber is suspect at this point. Just be glad you don't have the SC version with all those additional hoses!
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My own personal experience is that once these older hoses are disturbed that sealing is compromised. I replace the expansion tank recently had some resealing issues. A new upper hose and expansion tank hose + constant tension clamps are ordered.

 

If this is implying lying under a running car on Jack Stands, it might be the most dangerous advice I've read on this or any forum.

There is no need to heat the engine at all. A simple dye pack and pressure tester will disclose the leaks. You still may need to remove the under scuttle and put it on stands if you can't find the leaks from above. Follow the lead given by clubairth1 and add the UV dye. Your leaks will show themselves.