Jaguar XJ-S. Service manual - part 30

 
 

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Chemical contamination is combated by additives in the oil.  Eventually, however, the additives are consumed and fail 
to counteract the contaminants.  At this point, the oil needs to be changed. 

Physical contamination refers to metal particles and dirt in the oil.  The metal particles come from wear between 
moving parts.  The dirt comes through the intakes, and a portion makes it past the rings.  The problem is obvious in that 
such particles will increase the wear on bearings and the like. 

It is tempting to take comfort that the oil filter is preventing the particles from getting into the workings of the engine.  
Unfortunately, it is not as effective as one could hope.  The typical paper-element oil filter will catch particles down to 
about 30 or 40 microns, but damage is caused by particles down to about 2.5 microns.  These smaller particles build up 
in the oil and pass right through the filter, cycling through the engine again and again. 

The full-flow filter cannot be made with a tighter mesh because the restriction to oil flow would be too great.  In 
addition, if the filter gets clogged, either the element breaks open (dumping all the dirt into the engine), or the flow is 
inhibited.  Usually a relief valve is provided to allow oil to bypass a clogged filter, allowing crud of all sizes to circulate 
through the engine. 

There are two excellent ways to combat physical contamination.  The first is by installing a bypass filter.  A small 
percentage of the pressurized oil from the outlet of the full-flow filter is diverted into a separate filter with a tight mesh 
element to stop particles down to 2.5 microns, and from there right back into the sump.  An orifice is provided to 
prevent an excessive amount of oil from taking this route, which might starve the engine.  If the filter gets plugged, no 
problem -- the flow stops, and 100% of the oil goes through the galley as before.  But as long as a small amount is 
going through the bypass filter, within only a few minutes all of the engine oil is cycled through it and the amount of 
suspended particles is greatly reduced. 

The other method is essentially the same, except that the bypass filter is replaced by a centrifuge that causes the 
particles to collect on the inside of a spinning cylinder.  These are typically only available for larger engines. 

These solutions are even better than changing oil at short intervals.  Even with frequent oil changes, particles appear in 
the oil immediately and continue to build up.  The bypass filter, however, continuously keeps such particles from 
causing engine wear. 

Note that a bypass filter does not address chemical contamination.  Such an installation would be effective at reducing 
engine wear, but the oil needs to be changed at the same intervals to prevent the additives from failing. 

An outfit called TF Purifiner (page 717) offers a package that includes a bypass filter system along with a small heater 
that boils off water, fuel, and coolant to minimize the chemical contamination so the additives last longer. 

Surfing the WWW, Mike Claus found that other products are available from Baker Precision Bearing (page 711), Fram 
and Amsoil.  “Fram offers an automotive by-pass filter in its product line that features a pleated-paper element and easy 
“spin-on” replacement similar to original-equipment-type units.  Ask for the Fram “PB50” with mounting hardware. 

“Amsoil’s bypass unit is connected to the oil pressure sending unit and returns oil to the pan, thus requiring some 
mechanical ability or the services of your mechanic for the initial installation.  The company states that its bypass unit, 
which employs a user replaceable, pressed-fiber element, refilters all the oil in an engine every five minutes, and keeps 
it analytically sparkling clean for the (recommended maximum) element life of 25,000 miles!  It even extracts and 
contains any water that has (inevitably) condensed into the oil...which if allowed to remain in circulation will often 
result in the formation of corrosive acids.” 

Of course, one might immediately ask: if a bypass filter is such a good idea, why didn’t such a quality automobile as a 
Jaguar come with one from the factory?  Well, you have to consider the options the way the manufacturer does.  The 
lack of a bypass filter will not cause engine failure before some extended mileage, especially if the owner has been 
paying the dealer for oil changes on a regular basis -- and even if the engine does fail due to dirty oil, the manufacturer 
is not likely to incur any liability.  The additional cost, multiplying the cost per car times the thousands of cars sold, is 
significant.  And the additional risk of failure -- one of the oil lines to a bypass filter blowing open or some such -- may 
be more than the company wants to accept.  Just having to tell prospective buyers that there are two oil filters that need 
regular changing may be seen as a marketing disaster, especially in this era of drive-it-and-forget-it cars. 

 
 

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You, as the owner of the car, may think differently.  You have a significant investment in your car, the risk of a blown 
high-pressure oil hose is no big deal to you (messy, but not particularly expensive), and you are the guy who will have 
to pay for a new engine when this one wears out.  Basically, if you are the type to own a Jaguar for the life of the car, a 
bypass oil filtration system would be a wise investment.  Of course, if you plan on selling the car soon, or plan to crash 
it rather than wear it out, it’d be a waste of money. 

 

PRE-OILING BEFORE STARTUP:  A lot of the wear on any engine occurs at startup, when the engine must run for a 
few seconds before oil pressure is established.  Russ Lehman sends this tip:  “I’ve got a “Pre-Luber” on my van because 
it only gets driven about once a week or so, and the pre-lube brings the oil system up to pressure by pumping oil 
through the engine before starting.  These pumps are fairly common on marine engines for the same reasons. 

“The pump is fed from a line attached to the oil pan and pumps into a tap where the oil pressure sender is attached.  The 
pump allows oil to pass through the normal routes for normal engine operation, while not allowing oil to pass 
backwards through the pump (I think it’s a piston pump).  The motor is switched through the ignition key in the aux 
position (controlled by MOSFETS), and will stop when the engine ignition is switched on.” 

There are other systems, including a simple pressure reservoir that holds pressurized oil after shutdown.  During 
startup, a valve is opened, pressurizing the system before the starter is engaged. 

Note that such systems may be of limited benefit.  While the bearings in the bottom end of the engine may experience 
much less wear, it is not usually worn bottom-end bearings that require an engine rebuild.  More often, it’s worn 
pistons/rings/cylinders that eventually convince an owner it’s time for an overhaul, and a preoiler does little or nothing 
to reduce piston/ring/cylinder wear. 

 

ADDING EMISSIONS CONTROLS:  Huh?  Well, Germany now has a taxation system that penalizes cars without 
emissions controls so severely that many German XJ-S owners are seeking to retrofit.  For many years the German 
version had no catalytic convertors or oxygen sensors even though they were provided in the US. 

According to Jeffrey Gram, the following outfits (all in Germany) will install emission controls in cars that were not 
originally equipped with them: 

 

Ernst Apparatebau, Hagen, Tel +49 (0)2331 3600-0 

 

GAT-Abgastechnik, Gladbeck, Tel +49 (0)2043 24021 

 

Gutmann, Breisach, Tel +49 (0)7667 1091 

 

G+M Kat, Gladbeck, +49 (0)2043 42410 

 

HJS  Abfgastechnik, Menden, +49 (0)2373 9870 

 

Oberland, Garmisch-Partenkirchen +49 (0)8821 1036 

 

Oettinger, Friedrichsdorf +49 (0)6172 7053-55 

 

Walker, Viernheim, +49 (0)6204 738-0 

 

Waschkuttis, Wiesenthau, +49 (0)9191 96495 

 

Wurm, Stuttgart, +49 (0)711 420071. 

 

IF ALL ELSE FAILS:  Most Jaguar owners feel that if you want a Chevy, you should buy a Chevy.  But there are those 
who think otherwise, and for them there are several outfits that offer kits for replacing the Jaguar V12 with a Chevy V-
8.  John’s Cars (page 715) offers two kits for the XJ-S, one for a small block Chevy and one for a big block.  Another 
outfit to check with is Jaguars That Run (page 714). 

 
 

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The 90° V-8 is an excellent engine layout; it has even firing order, and its primary and secondary imbalances are 100% 
correctable by simply casting counterweights into the crankshaft.  The problems with the classic Chevy “lump” are not 
that it’s a V-8, or even that it’s cast iron; it’s problems are:  A) It has pushrod-operated valves, which require 
compromises in cam profile, which in turn generally means it’ll either produce lots of power or have a good idle but not 
both; and B) It employs a timing chain with no tensioner, which results in an engine that runs rougher and rougher as it 
wears.  Both of these problems were addressed and corrected by all major European automakers in the 1960’s, and by 
all Japanese automakers in the 1970’s.  Both Ford and Chevy finally introduced V-8 engines with overhead cams and 
intelligent camshaft drive systems in the 1990’s, apparently in response to competition from Lexus and Infiniti. 

Sir William Lyons, founder of Jaguar, apparently didn’t like V-8’s.  When Jaguar bought out Daimler in 1960, Daimler 
had two V-8 engines in production, and Lyons scrapped one of these immediately and the other a few years later.  
When it became apparent that the venerable Jaguar XK inline 6 would no longer cut the mustard, Lyons responded with 
the V12. 

If you must shoehorn a cast iron V-8 into your Jaguar, do yourself a favor and purchase some cast aluminum valve 
covers.  They will absorb a lot of the noise of the valve train.  A cast aluminum timing chain cover will also help reduce 
racket.  Replacing the timing chain with something with less slop, like a set of gears, will make the engine run 
smoother. 

Of course, a better idea yet would be to opt for the newer cast aluminum Y-block Chevy V-8’s.  Not only are these 
engines far superior mechanically to the cast iron models (despite retaining the pushrod valve train), they also come 
with modern EFI and ignition systems and improved automatic transmissions. 

 

 

IGNITION SYSTEM 

 

SPARK PLUG REPLACEMENT:  Note that this task is much easier on the pre-H.E. because the spark plugs are 
vertical.  On the H.E., the plugs are tilted inboard just enough to make the job truly miserable.  Most of the tips below 
were developed to deal with the H.E. 

First problem is getting the plug wires off -- and back on later.  Jan Wikström, who owns a pre-H.E.:  “I’ve made up a 
pair of “pusher” tongs out of a bent piece of 4mm high-tensile fence wire.  Same idea as the common barbecue tool, but 
the jaws originated as a short piece of 9mm copper pipe split lengthwise and brazed to the wire.  This gets a good grip 
on the cable just above the rubber cap on the terminal.  This tool needs to be bent to a slight angle above the jaws.”  The 
same idea might work on the H.E., but expect to have to vary the details to make it work well. 

Another idea is to use a length of 1/4” steel tubing and some bicycle brake cable to make a “snake grabber”. 

If you have access to a wet/dry vacuum cleaner, use the hose with no attachments to clean around the plugs before 
removing them.  Just poke the hose over the end of the plug.  Compressed air can also be used.  John Bertsche adds:  “I 
came up with a cool tool for cleaning out the crud around (and in) the spark plug holes.  A turkey baster -- pull off the 
bulb, duct-tape the other part to your shop-vac hose, and you’ve got a high-intensity, pinpoint (well, almost) vacuum 
nozzle that’ll fit right into the spark plug hole.  Works great!  You can use it to scrape dirt and crud out of almost any 
nook and cranny, and it won’t scratch the aluminum.”  Note that you can purchase a set of small vacuum attachments at 
Wal-Mart intended for cleaning things like computer keyboards, and those attachments would also work well here. 

Using normal tools, it generally requires removing the cruise control actuator and unbolting the A/C compressor on the 
H.E. to replace the 1A and 1B plugs.  Matthias Fouquet-Lapar says, “Jaguar offers a tool, it's in the rear-section of the 
XJ-S parts manual.  It fits perfectly and you don't need to remove the A/C compressor.”  Steve Holst says, “I ended up 
using the official Jaguar spark plug removing tool that came with the tool kit to replace the plugs.  It worked 
wonderfully and I didn't need to move the A/C compressor one bit.  I ended up unbolting the cruise bellows only.  I'm 
very glad I gave it a try.”  This plug wrench (CAC5368) comes in the XJ-S tool kit, but it’s amazing how often used 

 
 

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cars don’t have a tool kit.  If you need to buy the plug wrench, shop carefully; they supposedly can be had for under 
$20, but Jaguar dealers have been known to ask much more than that. 

Ah, but things are never that simple.  Peyton Gill says, “The tool's socket well was too shallow for the NGK plugs I 
installed.”  Graeme Mawson concurs:  “My car is an '85 V12 with NGK plugs; the tool provided does not fit over the 
plug, i.e. the stem of the plug is too long for the barrel of the tool!  Perhaps there are two different tools!” 

After much discussion about differences between types of spark plugs, it turns out that Mawson is correct -- there are 
two different tools.  The earlier tool, CAC5368 -- used up until at least Peyton Gill’s ’86 -- will not fit a spark plug.  
However, sometime later Jaguar revised the tool so it would fit a spark plug.  The two wrenches appear to be identical 
in construction, but the later version, CBC4096, has a hole in the top of the socket that goes all the way through; when a 
spark plug is in place, you can peer in between the pivot joints and see the top of the electrode.  Brian Schreurs says, “It 
does not come with the T-handle so one would have to buy a piece of rod and cut to fit.”  The T-handle is C36612/2, a 
part number for a straight piece of steel rod. 

Apparently, the spark plug tool part number was superceded again by CCC4813.  It’s not known what that difference 
is. 

It may be possible to modify the earlier tool by simply drilling a hole through it.  You’d hope that it’s not -- you’d hope 
the tool is made of harder steel than that -- but in fact it appears pretty soft and cheap and may be drillable.  John 
Bertsche says, “The factory tool I had in the trunk fit on them fine...just wasn't up to the stupendous amounts of torque 
required to crack them loose.”  David Littlefield says, “The factory tool is very cheaply made, frankly.  Mine has a big 
sticker on it with a British flag and says "Thanks for buying British!"  I kept ending the phrase in my mind with "in 
spite of the fact that you are spending half your weekend trying to change impossibly located spark plugs with the 
incredibly cheap, POS tool we supplied you."” 

There are T-wrenches sold for 5/8” spark plugs, and a good one might actually do the job.  Unfortunately, all this 
author has found are cheap ones -- even poorer quality than the Jag OEM tool -- and the swivel invariably breaks as 
soon as torque is applied with the swivel in any position other than straight, which makes them worthless for this task.  
Mawson says, “I have bought several box type tools to undo the plugs but as indicated above they always break or 
'round off' long before all 12 plugs have been removed.  Furthermore on the V12 without removing the likes of fuel 
lines, A/C compressor, cruise control, distributor or throttle mechanism, when the tool does break (with stupendous 
amounts of torque applied) it is more than likely that other things get broken as well (usually fingers or knuckles).” 

Littlefield says, “Another suggestion for an under-the-compressor tool might be to cut down an old spark plug socket 
that has the flats on it, and maybe even enlarge the ratchet hole so it can fit further down the plug.”  Using this idea, 
Larry Barnes made a tool that actually works:  “I took a regular spark plug socket and: 

1.  Removed the rubber thing in the inside. 

2. Ground 

off 

both ends so an open-end wrench would still work on the top part, and the bottom would 

still come to the "nut" part on the spark plug.  

“I use this modified plug socket for plugs 1A and 1B only.  Works great without removing the compressor.”  On the 
H.E., make sure to start with a 5/8” spark plug socket; most spark plug sockets are 13/16”.  All in all, this is probably 
the best way to go; it is easy to find a 5/8” spark plug socket in whatever quality you desire, they don’t cost all that 
much, and most of them have an external hex on the top.  Once you get the socket suitably cut down to fit past the side 
of the A/C compressor and onto a plug, you can simply use a box-end or open-end wrench on the external hex to get 
the plug loose.  Most importantly, if you’re careful you can apply serious torque without the slightest sideways force on 
the plug; many owners have ended up with plugs broken off at the top of the threads, which is not fun to fix. 

There is one more possibility in spark plug tools.  J Harper points out that Eastwood Tools (page 701) offers a 
telescoping spark plug socket.  This thing collapses into a little hockey puck which you position over the plug, and then 
telescopes into a socket shape around the plug.  Cute. 

Even with a workable tool, you might want to move the compressor anyway.  Fouquet-Lapar, despite having the plug 
tool, says, “I still remove the compressor and the throttle pedestal, mainly to clean things up at the same time.”  
Littlefield left the compressor in place and says, “after this experience, I think I know what surgeons go through during