Jaguar XJ-S. Manual - part 23

 
 

87

One other solution may be to replace the nuts with new nuts with the same thread but a smaller hex.  Make sure they’re 
Grade 8 or equivalent; you don’t want cheap, soft steel nuts here. 

Martin Karo:  “Better than the crowfoot solution, Hazet makes a tool for precisely this purpose.  It has 12-point box at 
one end; the shank is then bent vertically 90 degrees, and runs up 6 to 8 inches, depending on the size; then another 90 
degree bend brings the shank back over the box end, and a 3/8" square drive hole is bored in, directly over the box end. 
 This clears over-nut obstructions, and the torque values are correct no matter what the wrench angle.  I rented one the 
last time I replaced a cylinder head, and it worked great.  To buy, however, I dunno... if it's a Hazet, you can be sure it 
ain't cheap.” 

You could, of course, make a wrench that fits Karo’s description.  Find a box end wrench that fits the nut, and heat it up 
and bend it 90° straight up.  Cut the other end off and weld on a socket, any socket, to provide a square drive 
connection. 

The purpose of torquing head nuts to a specified value is to obtain a certain amount of tension on the studs themselves.  
Whether or not the threads on the nuts are lubricated makes a huge difference in how much tension results from a given 
torque, as does whether or not the contact between the nut and the steel washer it sits on is lubricated.  Unfortunately, 
the manuals are not as clear as they might be on whether or not the specified torque is intended to mean with or without 
lubrication.  In its section on General Fitting Instructions, the ROM does say “Always oil thread lightly before 
tightening to ensure a free running thread, except in the case of self-locking nuts.”  This makes sense, since tension 
obtained from lubricated threads is more consistent than from non-lubricated threads; if the threads aren’t lubricated, 
there’s no telling how much tension you’ll end up with.  There seems to be little or no official guidance for lubricating 
the washer face, though. 

This author recommends you lubricate the head stud threads with anti-seize compound; this may not sound like oiling 
lightly, but the amount of friction in the threads when installing should be comparable.  Plus, the anti-seize compound 
will ensure the threads are not damaged when retorquing or removing the nuts later on. 

This author also recommends you apply a non-hardening sealant to the contact areas between the washer and the head 
and between the nut and the washer on the 7/16” studs only.  On ten of the fourteen 7/16” studs per head, these contact 
areas seal the coolant circuit; that’s why these nuts are cap nuts, since coolant can’t leak through the threads on a cap 
nut (and you thought Jaguar used cap nuts to make it pretty!).  While not originally intended as a lubricant, the sealant 
will provide a fairly consistent amount of friction between the nut and the washer and therefore a consistent application 
of tension to the stud.  By using a non-hardening sealant, you hopefully leave open the possibility of retorquing later on 
-- although presumably you could retorque by removing the nut completely, applying fresh sealant, and reinstalling. 

On the 3/8” studs, apply anti-seize compound between the washer and the nut.  You can leave the contact surface 
between the washer and the head dry, apply sealant, apply anti-seize compound, whatever, it shouldn’t make any 
difference. 

Needless to say, if any of the threads on studs or nuts are boogered up enough that the nut won’t spin on freely, they 
must be cleaned up or replaced before torquing. 

When torquing down the nuts, aim for the low end of the spec range, and be alert for signs of stud yielding:  the nut 
continues to turn without the torque increasing any more.  If the specified torque is attained in a smooth and progressive 
manner, there is nothing else to worry about; the head is on and secure, and there is sufficient tension on the studs to 
make sure the head gasket will remain sealed.  On the other hand, if either the threads or the washer face is assembled 
dry, you won’t know how much of your tightening torque was lost there, so you won’t know just how much tension 
actually got applied to the stud -- and therefore you won’t know how long your head gasket is going to last. 

 

 

 
 

88

Engine Work -- Front 

 

CRANKSHAFT DAMPER/PULLEY REMOVAL:  First note that, contrary to the repair manuals, it is not necessary to 
remove the crank pulley to get the water pump off. 

Also note that what looks like a bolt head in the center of the crank pulley is actually a hex fixture for turning the 
engine by hand.  Two smaller bolts must be removed to remove this hex, and the real pulley retaining bolt is 
underneath.  Then one more note:  Since you already have the belts loose or off, you can remove two more small bolts 
and remove the pulley from the crank damper entirely.  This provides much better access to the big crank damper bolt 
so you can use a box end wrench or some such. 

What size wrench fits that bolt head?  Craig Sawyers:  “That damned thread is a 7/8 inch BSF.  The AF measurement is 
1.300 inches for that thread.  I got a 7/8 BSF, 3/4 Whitworth socket to do the job.”  See page 24 for more info on 
Whitworth/BSF, including ideas on finding tools. 

If you can find a 33mm socket, it’ll fit perfectly.  Unfortunately, even numbers are the standard in larger sizes, so it’s 
pretty hard to find anything closer than 32mm or 34mm.  Hard, but not impossible; Jan Wikström says, “I have a cheap 
Taiwanese socket set from the flea market; it has every mm size from 12 to 35.  There are far more sockets than the ISO 
standard sizes, but the odd ones can come in handy.” 

Bob Christie says you can get 33mm sockets from MSC. 

Apparently 33mm is a common size for truck lug nuts.  Walter Petermann found this site that has 33mm sockets listed 
under “truck wheel sets”: 

Independent Equipment & Supply Co., Inc. 
1-800-837-4343 (Continental USA) or (740) 776-2154 
FAX:  (740) 776-2429 

http://www.indequip.com/grey3_4.htm

 

e-mail ies@indequip.com 

Wonder of wonders, they sell 33mm sockets individually; you don’t need to buy a whole set of truck lug sockets to get 
the damper bolt socket you need for your Jag.  Their prices aren’t bad, either. 

You might want to avoid the smaller drive sizes here.  Robert Warnicke says, “I broke two 1/2” drives before I finally 
removed the bolt with a pipe wrench.” 

If nothing else works, you can use a file or grinder on the hex to make a 1-1/4” or 32mm socket fit.  You can just use a 
big adjustable wrench (or Warnicke’s favorite, the pipe wrench) to get it loose, but you will still need to find a socket 
that fits to carefully torque it during reassembly -- which is of considerable importance, as described in the discussion 
of key failures below. 

To loosen and retighten the bolt, it is necessary to hold the crank still.  You can remove the starter to jam the flywheel, 
but that is definitely the hard way.  An easier way would be to use the access hole on the left side of the engine, the one 
with a rubber plug and intended to provide access to the torque convertor mounting bolts.  Michael Neal provides an 
even simpler access:  Just remove the cover from the bottom of the torque convertor housing. 

Of course, on my car I can just put it in 5th gear with the emergency brake on! 

Matthias Fouquet-Lapar suggests:  “Once you have removed the upper part of the pulley (the one which drives 3 belts), 
you can easily use its 2 screws to attach a home-made bar on the damper.”  This is perhaps the best method of all, since 
pulling this lever and the torque wrench together works really well when trying to carefully torque that bolt up on 
installation. 

Besides holding the crank still, there’s also the problem of getting the bolt loose.  One idea that solves both problems 
would be to use an impact wrench -- the way an impact wrench works, the inertia of the crank is all that’s necessary to 
hold it still.  But there’s not enough room in the car to use an impact wrench, so that will require either pulling the 
radiator or the engine. 

 
 

89

Shane Mantoszko says “use a good long-handled socket/torsion wrench, put it on the front crank nut, brace it on a 
strong part of the engine bay, disconnect the coil, and then turn your ignition key for a few quick bursts, and viola, the 
crank nut will be loose...” 

Dale Knaus says, “I used what we call a "slug wrench".  It is a box end wrench made extra heavy with a striking pad on 
the other end.  It is made to hit with a hammer to tighten and remove nuts.  I borrowed the tool from the industrial plant 
where I work; they are probably available from industrial tool supply companies.” 

Regardless of how well these methods may work getting the bolt loose, remember that you’ll still need to deal with 
reinstallation.  Since the bolt torque is critical, you’ll definitely need a suitable torque wrench and socket and you’ll 
probably need that restraining lever Fouquet-Lapar suggests.  All that being true, you might as well go ahead and 
acquire those items and see if they’ll get the bolt off to begin with. 

 

CRANKSHAFT PULLEY - SHEARED WOODRUFF KEY:  Paul Konitshek, Michael Neal and several others report 
that the woodruff keys that align the crankshaft damper/pulley are a known problem area.  The keys may become worn 
or totally sheared, allowing the pulley to reposition itself around the crank. 

The immediate effect of this slippage depends on which ignition system you have.  If you have a pre-1989 car with 
Lucas ignition, you might not even notice unless things get really bad and start chewing up parts.  Neal reports:  “It 
almost never gets to the point where the pulley comes loose.”  If it merely slips, it usually won’t become apparent until 
you try to set the ignition timing; the timing marks are now completely wrong, so you’ll get really confused.  If you 
have the later Marelli ignition system, the damper slipping will immediately screw up the ignition timing since the 
sensors are on that damper. 

Note that there are two keys used.  There is a “split cone” that is similar to those used on industrial pulleys.  The pulley 
fits onto the outside tapered surface of the cone and is aligned with one key.  The cone slides over the crank and is 
aligned with another key.  When the bolt securing the pulley is tightened to specification, the split cone compresses 
securely onto the crank like a collet in a chuck. 

Roger Bywater, who was in charge of belt drives for the V12 at Jaguar at one time, explains:  “The purpose of the 
keyway is purely for location and accurate alignment during assembly.  In almost all assemblies of this type the key is 
not intended to transmit any torque, indeed it is not strong enough, the friction of the tightened joint is meant to do that. 
 There must always be some clearance around the key so if the joint comes loose torsional vibes will always fret and 
destroy the keyway.  Many later engines do not have keyways anywhere, relying only on friction.  The Jaguar V8 
camshafts are typical with the timing sprockets just placed on the end, timing marks all lined up, and nipped up very 
tight with a central bolt - that's it.  If they come loose the sprocket can just spin round - only it never happens. 

“The answer is to make sure the friction inside and outside the cone cannot fail so the bolt needs to be tight to the point 
of yield to keep the whole assembly under tension.  Possibly the bolt tightening figure is marginal at the lower tolerance 
quoted of 125 ft-lbs so maybe the top figure of 150 ft-lbs should be the rule.  In fact the AJ6 manual quotes 203 
Newton Metres (with no tolerance) which equates to 150 ft-lbs for the same size bolt which seems to support this 
view.”  Note that the threads need to be “lightly lubricated” for the torque readings to be anywhere near correct; this 
author recommends anti-seize compound, which will also help get it apart next time. 

If the torque is supposed to be transmitted via friction between crank and cone and between cone and damper, 
obviously it’d be a good idea not to put any anti-seize compound on those mating surfaces.  In fact, you might want to 
be careful there’s no oil on them -- although hopefully it’d get squeezed out while torquing. 

So, if the torque is supposed to be transmitted via friction, how come the Jaguar V12 has a history of key failures here? 
 Neal:  “It seems only to happen if water has gotten into the nosecone on the crank.  The area is always very rusty when 
the front pulley is removed.  The woodruff key is either broken or eroded away from the rust.”  Of course, this area is 
exposed to the elements, there’s no keeping water out of it; whether or not these parts rust probably depends on whether 
the crank seal is keeping them well oiled.  Perhaps they all rust, and Neal only notices the ones that have sheared keys 
are rusty because those are the ones he has to work on. 

 
 

90

The failure history could be because the engineers at Jaguar screwed up, either underestimating how much torque this 
joint would need to transmit or overestimating how much torque the joint could handle.  However, it’s entirely possible 
that most or all of these failures came from somebody not torquing that damper bolt down adequately.  Even presuming 
they were torqued correctly at the factory (!), mechanics are always fiddling around in this area -- such as when 
replacing a leaky crank seal.  Perhaps some of the mechanics are not being as meticulous as they should be in applying 
full torque during reassembly.  Take a lesson: make very sure you torque that bolt properly!  Just zipping it on with an 
impact wrench is unacceptable. 

Neal:  “In some cases the slot in the crank is widened a bit but a new key usually secures it substantially.”  If the crank 
has been boogered up too much by the damper slipping, of course you have to install a new crank.  Yeah, right.  Even 
Bywater himself reassembled an engine with a damaged keyway in one of his AJ6 development cars by “drilling and 
pegging” the split cone during installation.  “Obviously loctite or similar would create difficulties in any future strip 
down so if everything is clean and in good order and fully tight there should be no need for it.  Where things are less 
than perfect then pragmatism must rule.”  It might help if you file the high points off the gouges on the crank and use a 
new split cone. 

 

CRANKSHAFT PULLEY - GETTING THE KEY OUT:  Sometimes the keys won’t come out, notably the key on the 
crank itself.  Suggestions include using a pair of angle cutters to grab it and walk it upwards, and using a suitable chisel 
to cut under the key to pry it out.  The suitable chisel needs to be a hair narrower than the key, and can be made from 
old lathe bits or “cut nails”.  Cut nails are made from flat stock, giving them a sort of trapezoidal shape, and are really 
hard for pounding into masonry.  Greg Guillaume:  “Here’s what I did:  Get a 1” chisel, lay it on the crank, 
perpendicular to the crank, up against the key.  Then whack away with a hammer on the opposite side of the chisel.  
The shape of the chisel is just right so it bites into the key, the 1” width hangs over the end of the crank, and you get a 
lot of room to swing the hammer.  Of course, the chisel is a little beat up, but it worked great.” 

 

CRANKSHAFT PULLEY - SPLIT CONE PROBLEMS:  Dan Jensen says, “The split cone was broken in three places. 
 Rather than pay $$ for a replacement, I just stuck it back into the damper/pulley with Hylomar sealant and gently 
replaced it.  It centered properly and has worked great for 35K miles.” 

 

CRANKSHAFT PULLEY - RUBBER DAMPER PROBLEMS:  Chris Yewdall owns a ’91 convertible, and started 
having noise when operating the roof.  “When lowering the roof with the engine running, a squealing noise is heard 
from under the hood until the roof is fully lowered.  After a few more months/miles the squeal happens most times you 
start the car for a few minutes until the revs build up as you drive away.  Eventually, the voltage on the battery charge 
guage on the dashboard drops to 12V (about 1/4 of the way up the guage) and the battery goes flat.  Occasionally, the 
alternator will charge normally or just below normal, particularly on a freeway journey.” 

Sounds sorta like a loose belt problem, but it wasn’t.  After wasting too much money on things like an alternator 
rebuild, the problem turned out to be the crank damper itself.  When he got the failed part back from the mechanic, he 
reported on it:  “On inspection, it is the bond between the inner pulley (which keys onto the crankshaft) and the rubber 
damper which has failed since the inner pulley rotates freely on the inner surface of the damper.  The rubber has 
hardened to the point where it has cracked in lines between the inner and outer pulley.  It feels more like bakelite or 
plastic and has no flex at all.  Believe me, it’s not hard to spin the outer by hand.”  The other three belts are driven by 
rigidly-mounted pulleys but the alternator belt is driven directly from the outer ring of the crank damper, so this rubber 
breaking loose causes drive problems for the alternator. A heavy alternator load, such as operating a convertible top, 
aggravates the problem. 

If you’re having trouble confirming if your damper has sheared, put a mark on the center portion and a mark in line 
with it on the outer portion.  Run the car for a while, then shut it off and check the marks.  If they are no longer aligned, 
you need a new damper. 

Interestingly, this type failure was apparently unknown on the earlier cars with Lucas alternators driven by V-belts.  
Those cars also had Lucas ignition systems, and the timing marks for setting the ignition timing were on the outside