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Cooling Systems on the XJS — What’s Normal, What Isn’t

Published: 20th January 2026

Ask almost any XJS owner about cooling and the conversation quickly turns to anxiety: rising gauges, fans cutting in, and memories of overheated classics on summer days. In reality, Jaguar engineered the XJS to operate across a wide temperature range, and much of what causes concern today would have been considered normal behaviour when the cars were new.



Understanding the XJ-S Cooling Philosophy

The Jaguar XJS was produced over more than two decades and fitted with two very different engine families: the AJ6 straight-six in 3.6- and later 4.0-litre form, and the long-serving V12 in 5.3- and later 6.0-litre form. While the cooling layouts differ in detail, the underlying philosophy is the same — manage heat effectively under load, not eliminate all visible temperature movement.

Unlike many modern cars, the Jaguar XJS does not attempt to disguise temperature changes. Its gauges reflect what is happening within the cooling system, and some movement of the needle is both expected and normal.

Why XJS Cooling Systems Are Often Misunderstood

Modern vehicles have trained drivers to expect a temperature gauge that rises to a midpoint and remains there indefinitely. The XJS predates that approach.