I noticed the temp gauge was steadily increasing yesterday as I was driving. I pulled over for a bit and then loosed the pressure cap. I proceeded on my journey and the temp gauge normalized. When I returned home I tightened the cap fully and took her for ride and the temp gauge began increasing again.
Does the cap simply need to be replaced or may there be other issues?

 

Welcome to the forum Crownjag,

Although overheating is not an engine killer on the straight six engine the way it is on the Jaguar V8, it should still be investigated promptly.

It could be as simple as a failing pressure cap if there is no associated history of the vehicle losing coolant.

Jaguars don't normally 'use' coolant. If you are regularly topping up or get an abnormal overheat like this, there is the possibility of a leaking hose / hose clip / sticking thermostat / failing water pump. All of these will lead to overheating.

When you get a minute, please follow this link New Member Area - Intro a MUST - Jaguar Forums - Jaguar Enthusiasts Forum to the New Member Area - Intro a MUST forum and post some info about yourself and your vehicle for all members to see.

In return you'll get a proper welcome and some useful advice about posting to the forum.

Graham

 

Loosing the pressure cap is probably counter productive. Water boils at a higher temperature when it is under pressure. What you DO NOT want is for the coolant to boil out and leave nothing in the system to cool the engine. Again, how did you determine something was amisss/ Where on the scale did the guage go to?