We discuss how to make your Jaguar V12 last forever
IN HIS autobiography of his time at the helm of Jaguar, Sir John Egan described the Jaguar V12 as the company’s ‘gentle giant’ which is a neat way to sum up the iconic powerplant. With its inherently good balance, a chain-driven single cam per bank, two-valve per cylinder layout and a conservative power output it’s an understressed unit which in theory should be capable of supreme longevity.
There’s no denying however that a 12-cylinder internal combustion engine is a complex entity and no matter how good the fundamental design may be, there’s massive scope for drama once it’s squeezed into an engine bay and plumbed into cooling, lubrication and fuelling systems.
In the E-Type with its fully opening nose cone, the V12 seems relatively approachable for the enthusiastic DIY owner – it’s all pretty familiar, although there’s a lot more of it. In the tighter confines of the XJ-S bodyshell though, and festooned with injection and air conditioning plumbing, things are rather more daunting for the home mechanic, with barely a hand’s width around the installation. It’s this which perhaps results in the less than perfect maintenance record of so many examples, but talk to the experts and they’re generally agreed that with the right care, attention and knowledge, the Jaguar V12 can be a trouble-free proposition even in old age.
Having specialised in the XJ-S for many years, KWE is more familiar with the engine than most, so we sat down with the company’s Chris Knowles to find out how to make your Jaguar V12 last forever.
COOLING
In theory, there’s no reason why the XJ-S should suffer from any cooling issues: the system was designed and tested to run both in Arctic and desert conditions with a radiator big enough to run the car in Death Valley, meaning that in theory the British climate shouldn’t be a struggle.
As Chris points out though, the reality is that the system may have been entirely adequate as designed, but there isn’t much additional margin, meaning that age and indifferent maintenance can quickly cause issues – and a hot summer’s day on a stationary M25 with the air conditioning working hard can often be the final straw.
As a result it’s the cooling system which in practical terms is the engine’s Achilles’ Heel and Chris emphasises the need to start with the basics. And it doesn’t get much more basic than the coolant itself.
Like most engines, the aluminium V12 relies on the anti-corrosive properties of coolant to prevent internal corrosion which over time can cause a gradual drop in efficiency. Waterways, pipes and the radiator itself will eventually silt up and clog entirely, causing havoc which can be expensive and complex to remedy.
