In reply to a message from Hans G. sent Sat 26 Jan 2008:
Welcome to the XJ40 forum.
The AJ6 engines in the XJ40 are pretty much ‘bullet proof’
and I don’t think there is an iota of difference between the
3.2 and 4.0 litre as regards reliability / longevity. The
3.6 was phased out in 1990.
The basic engines ‘suffer’ from a very few minor problems.
Exhaust valve guide wear which allows oil to drain down the
guides past the stem seals after engine shut-down causing a
slight puff of blue smoke on the first start of the day -
but that can be eliminated / limited by use of the
appropriate 20W/50 engine oil
Some engines have suffered burnt exhaust valves - but
perhaps due to air leaks in the inlet tract on that cylinder
causing a weak mixture.
Some earlier engines with a poorly designed head gasket leak
oil from the transfer port between head and block for the
camshaft oil feed. (Check the area behind the distributor
for signs of oil collecting in the crankcase web).
Overheating due to poor maintenance / loss of coolant can do
some damage to the engine - warped heads are not common but
As regards fuel consumption, how hard do you drive?
My 4.0 litre with full-time aircon and the tranny always in
‘Sport’ mode (not available on 3.2 litre) typically averages
24.5 mpg on a tank full - admittedly with limited town driving.
Well in excess of 200,000 MILES should be no problem on an
AJ6 engine - I don’t recall anyone on this list having to do
a major engine overhaul involving re-bores or bearings.
Timing chains too are not a problem.
I advise you to make sure that everything else on the car
works to perfection - engine management system, (no ‘Check
Engine’ fault codes), air conditioning and heating, ABS and
brake boost, lighting (no bulb fail module warnings or fuse
warnings on the dash). Check also for uneven tyre wear front
or rear (in case the worn fronts have been swapped to the
back) and do not accept vague steering as ‘they all do that
Sir!’ - they do not.
Finally, if fuel consumption is a major worry for you -
perhaps a Jaguar is not the car to buy.–
The original message included these comments:
I’m thinking of buying an XJ40 and recently found what I
consider to be a reasonable offer. It’s a 1993 XJ40 4.0L
from Switzerland w/ 100.000 km. The seller told me this
engine would be the most reliable, and was less prone to
failure than the 3.2 and 3.6L (it would even consume less
My question: Is that correct? What mileage might I expect to
do with this car / engine (I was told it would be good for
at least another 150.000 km)?
Bryan N, '91 Sovereign 4.0 L, RHD (exiled in US)
Cambridgeshire, United Kingdom
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