Jaguar XJ-S. Manual - part 54

 
 

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Lenny Berk did this job, and had the following suggestion:  “Removing the engine breather filter housing (two 
bolts) made my life a little easier to get the crossover pipe in.”  The breather housing is the thing on the front of the 
left head, just forward of the oil filler. 

Berk also was less than satisfied with the lubricating qualities of hose sealer when fitting the cross pipe.  
Suggestions for alternatives include water pump lubricant, intended as an additive to coolant.  Care must be taken 
when selecting a lubricant, since the wrong stuff may attack the hose material or otherwise screw up the cooling 
system. 

This author found another way to install this pipe: remove the engine breather housing, and unbolt the A/C 
compressor and shift it rearward a couple inches.  Then, fit the left end of the cross pipe to the hose on the B bank 
thermostat housing with the right end of the cross pipe up in the air.  Then swing the pipe down, inserting the fitting 
into the hose on the water pump as you do.  Finally, connect up the right end, which is easy.  Tighten the clamps 
and reinstall the breather housing and the A/C compressor. 

When installing this cross pipe, try not to insert it too far into the hose connecting it to the water pump.  Positioning 
the cross pipe a hair too low makes it considerably more difficult to get a socket on the bolts holding the front 
support plate for the A/C compressor.  With the cross pipe properly located, the bolts holding the bottom of the 
support plate to the engine are easily accessible below the pipe, and the bolts holding the compressor to the support 
plate are easily accessible above it. 

 

A/C V-BELT RUB:  If the V-belt rubs against the cross pipe, it’s because the cross pipe wasn’t installed correctly.  
There are no brackets to hold this cross pipe in position; it is held only by the hoses connected to it.  If it rubs the V-
belt, the ends of the cross pipe were not inserted far enough into the hoses connecting to the thermostat housings.  
Usually, the clamps can simply be loosened and the pipe pushed into the proper position, and the clamps 
retightened.  Note Jim Isbell’s warning above to take care not to install it too far rearward causing the small hose to 
the header tank to rub on the crankcase breather mount bolt. 

 

CROSS PIPE REPLACEMENT:  If you’ve had the cross pipe out, you’ve probably been alarmed at its condition.  
It’s cheap steel, and usually is so pitted and corroded that it’s amazing it doesn’t leak like a showerhead.  It also is 
reportedly atrociously expensive from Jaguar, and you really don’t want to be searching the junkyards because the 
ones you find there are likely to be just as corroded.  Mark Jackson suggests an alternative:  “Cathouse Spares offers 
a third-party solution.  Cathouse can provide stainless steel rails acquired from an anonymous source for about 
$AUS135 (~$US95) plus the usual costs of mail & handling.  I've seen one and it looked pretty good - had all the 
bells and whistles - just a little "choppy".  The angles from memory were mostly welded instead of smoothly bent, 
but it looked pretty spiffy anyway.”  Cathouse Spares is listed on page 689. 

Of course, it’s just plumbing.  You could conceivably make your own.  One possibility is to find suitable copper 
piping and fittings and solder or braze the whole mess together.  The fill cap might be a bit of a challenge, but 
there’s no good reason it has to be a conventional radiator cap; any opening with a suitable watertight cap should 
work.  Or perhaps you could rip a radiator cap connection off the top of a brass radiator and solder it on.  The 
trickiest part may be at the pump inlet itself, where the connection from the header tank seems to protrude down the 
center of the pump inlet connection.  It’s not known how critical this is, since all lines lead to the pump inlet sooner 
or later; perhaps a simple cross fitting would work. 

You might even be able to replace the entire cross pipe assembly with straight sections of tubing, tees, and suitable 
hoses and clamps.  Note that this is the suction side of the pump, so it might be a good idea to use hoses as short as 
possible and insert metal coils to prevent collapse. 

 

CROSS PIPE HOSES:  John Napoli decided to cut pieces from commonly available hoses to connect the cross pipe. 
 “I did find Dayton hose numbers D71458 (smaller ID hose [to heads]) and D71316 (large ID hose [to water 
pump]).  These were fairly inexpensive.  They may not be the cheapest or the best donor hoses to use, but they seem 

 
 

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ok.  The smaller hose has enough material to cut at least four hoses, and the other two, so I will have a complete set 
of spares.”  All of the cross pipe hoses are short, straight sections, so it’s probable there are dozens of readily-
available hoses that can be cannibalized similarly. 

 

WATER PUMP LUBRICATION:  On the top of the water pump is a setscrew with a locknut on it.  This setscrew is to 
prevent the outer race from rotating in the housing, and either inserts into a hole in the bearing or tightens onto a flat.  If 
it inserts into a hole, you can remove the setscrew and screw in a zerk fitting (available at any hardware or auto parts 
store -- yes, it’s even the right thread), and then you can grease the bearings with a grease gun.  Be sure to reinstall the 
setscrew when you’re done. 

 

WATER PUMP SEAL FAILURE:  In the water pump housing there is a small drain hole that leads from the space 
between the seal and the bearing out the bottom of the pump.  As a result, when the seal fails the coolant comes out the 
bottom rather than through the bearing.  This is actually fairly standard practice in water pump design. 

 

WATER PUMP REBUILD PARTS:  If you are visualizing a water pump seal as similar to, say, the simple crankshaft 
lip seal on the front of the engine, allow me to improve your mind.  A water pump seal is considerably more involved.  
It consists of a non-rotating face that is spring-loaded in the axial direction (parallel to and surrounding the shaft) to 
hold it against a rotating seat.  These two parts run against each other with spring pressure holding them in contact, so 
they are made of materials that should provide long wear as well as a good seal: a carbon face against a stainless steel 
seat in good ones, a plastic face against a brass seat in cheap ones.  And, of course, the level of polish of both surfaces 
is important, so the rotating seat is replaceable and is sold as part of the seal. 

There is an elastomer involved, but only to connect the spring-loaded face to the seal housing so that it is free to move 
axially to contact the seat but fluid won’t leak around behind it.  The elastomer is therefore not really a wear item, 
although it certainly can be the item that deteriorates! 

The housing material is sometimes specified, commonly either brass or stainless steel.  It’s hard to care; the housing 
isn’t going to be the part that fails.  I suppose it may be important in industrial applications with corrosive fluids. 

The Jag water pump seal is an industrial standard; it can be found in any industrial equipment supply store, such as 
Grainger, as a type 68 shaft seal.  In fact, Grainger offers two seals that will fit:  Catalog #1R306, which has a black 
plastic seal face and a Buna diaphragm and is rated -40° to 225°F, and #1R324, which has a carbon seal face, a Viton 
diaphragm, and is rated -20° to 350°F.  The Viton one costs ten bucks more than the Buna.  Both of these Grainger 
seals have stainless steel rotating seats.  After buying a rebuild kit to get the bearing, Sean Straw described the seal 
included as having “...the characteristic plastic seal ring material, meaning these are likely the Buna version.  The seal 
face is very different in quality vs. the Viton one I purchased.  If you're a stickler for precision, get the Viton one -- the 
differences are not just in the seal rubber - the face of both the seal and the seal washer are much better in precision on 
the Viton - it's polished, whereas the Buna is a bit more coarse looking (it doesn't look super porous, but it is obviously 
not polished).  How much of a difference it'll really make in this application is questionable, but for the cost of parts, I 
think it is worth it.” 

Straw goes on to report that the seal has an industrial standard designation:  RS 80613.  “That's the Buna version -- 
append a V for the Viton one.” 

When the author’s pump needed rebuilding, it was because that diaphragm in the seal had failed; it’s unknown just how 
prevalent this failure mode is, but why not go with the Viton seal and not worry about it any more?  225°F isn’t all that 
far from the operating temperature of this engine, not even considering its tendencies to exceed that operating 
temperature.  Meanwhile, if you ever exceed the -20º limit on the Viton seal, you’d better have a good antifreeze mix. 

The bearing is also a fairly standard item, similar to those used in many common water pumps.  In case you’re not 
familiar with water pump bearings, the outer race is a long cylinder as though there are at least two rows of balls or 
rollers inside.  The shaft itself is part of the bearing, and presumably the inner race is machined directly onto this shaft.  
Straw provided the critical dimensions for the Jaguar part: the bearing outer race is 1.500” OD and 2.1280” in length.  

 
 

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The shaft is 4.9025” long overall, with 1.7745” of this protruding from the rear of the bearing.  The portion of the shaft 
protruding from the rear has an OD of 0.6300” to fit the seal and to press fit into the impeller.  1” of the shaft protrudes 
from the front of the bearing, and this portion has an OD of 0.7500” to press fit into the pulley flange. 

Finding a bearing supplier may be difficult, however.  The easiest way to get one may be to purchase a rebuilt water 
pump for another type car from a discount auto parts store and remove the new bearing (and perhaps the seal as well) 
from it.  After rebuilding your water pump, return the disassembled pump along with your old bearing for the core 
refund. 

When used in a Chevy or some such, this bearing would be press fit into a cast iron housing.  On the Jaguar V12 water 
pump, however, apparently a press fit into aluminum wasn’t considered reliable, so in addition to the tight fit a small 
threaded stud is screwed into the side of the housing and into a recess in the side of the bearing outer race to positively 
hold it in place.  All such bearings seem to have a hole or notch that will work, possibly originally intended to line up 
with grease fittings in other applications; if you happen to find one that’s totally smooth, you could easily grind a small 
flat on it. 

Rebuild kits for this pump are available at reasonable prices.  Straw reported that the kit he received from XK’s 
Unlimited (page 694) included the bearing, seal, impeller (cast iron), two gaskets, and a replacement stud and nut for 
holding the bearing in the housing.  The author purchased a kit elsewhere and received only the bearing and seal, so 
take note and ask what is included before ordering. 

Despite all the above availability, Dan Jensen suggests you forget about rebuilding the pump yourself and simply buy 
a rebuilt pump.  It isn’t that much more money, and unless you have things like presses around it’s easy to screw up 
a DIY rebuild job.  Don’t even ask Jaguar for a new pump, though -- you can’t afford it. 

 

WATER PUMP REBUILDING:  Some, but apparently not all, water pumps have a single countersunk Pozidriv screw. 
 According to Thomas Alberts, it is a common mistake to overtighten this screw, resulting in a fracture of the aluminum 
casting surrounding it.  Apparently the casting was designed for a non-countersunk bolt, and adding the countersinking 
makes the metal too thin for serious tightening.  If you wanna make sure the pump doesn’t leak, use a good sealing 
compound; don’t overtighten this screw. 

 

WATER PUMP CORROSION:  There is apparently some history of the water pump housing getting corroded; nobody 
seems to know if it is as a result of pump cavitation, bad antifreeze mixture, or what.  Randy K. Wilson says, “The 
place at which they corrode away is at the lower part of the water pump cavity.  This is behind the impeller area, but not 
the working side of the impeller.  The area should be a fairly low flow area on the high pressure side of the pump.  But 
it’s close enough to the output side of the impeller that turbulence could be present. 

“Whatever the cause, I do see the corrosion pitting often enough.  There may be a clue in that it’s not very often when 
merely changing water pumps; I see it on engines being rebuilt.  Engines get rebuilt because they have done some high 
mileage, or have been abused/neglected.” 

 

FAN TIP RUB:  If the tips of the blades on your fan show signs of rubbing, the problem may be in the transmission 
mount -- see page 341.  If you have a metal fan, you can hear it happen: you nail it from a standing start, and get a 
deafening screech from under the hood like all hell broke loose.  A bad, or an incorrectly assembled, transmission 
mount allows the engine to pivot around on the engine mounts, causing the fan to rub. 

A fan tip rub may also be caused by a failure of the left side motor mount.  When stomping it in low gear, a lot of 
torque is applied to the drive shaft.  According to Newton, this means that the same amount of torque is applied to the 
engine/transmission assembly in the opposite direction.  The engine tries to tilt to the right, applying tension to the left 
motor mount that was really designed for compression only.  If this rubber mount is torn, the entire engine will lift right 
up off its mount, causing the fan to rub. 

 

 
 

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PLASTIC FAN CRACKING:  Issue 68 (June 1996) of Australian Jaguar Magazine:  “Graham Cummins has recently 
found that the main plastic fan on the H.E. is prone to cracking and breaking up which can cause immense damage 
under the bonnet.”  Any guesses as to how Mr. Cummins discovered this problem?  Are you gonna find it the same 
way? 

Mark D. Stoner did.  “My yellow fan decided to explode one day when shifting at full throttle from 1st to 2nd gear.  Put 
a nice dent in the top of the hood along with shredding the steel fan shroud and blowing a huge hole in the radiator.” 

Lee Opausky wrote:  “Yes, the yellow plastic fan is cracked at the front.  When questioned, the shop foreman of one 
prominent Jag dealership told me not to worry, the crack on his XJ-S is ½” wide!”  More proof that you can’t trust the 
dealers for good advice. 

Jim Isbell ordered a replacement fan, and reports that the fan he was shipped did not look like the original.  “It is 
black and has a flat center metal piece.  The old one was white (now yellow) and the center piece was dished.  The 
old one had a lower aspect ratio (short and fat) to the blades while the new one has the higher aspect ratio (long and 
skinny).  The black flat one makes up for the “dishing” by offsetting the plastic instead.”  With any luck at all, this 
means that Jaguar has recognized the problem and redesigned the fan, and this new one won’t have cracking 
problems.  By the way, some of us believe the original fan was yellow to begin with, not white. 

The black plastic fan may be an improvement, but to be safer still it may be preferable to just go ahead and replace 
the belt-driven fan with electric fans as described beginning on page 219. 

 

FAN CLUTCH TYPE -- EARLY VS. LATE:  The early XJ-S fan clutch mounts with one bolt, the later with four.  
Mike Morrin points out that his ROM (Ed 4) appeared to have the two confused.  “On page 26-3, section 26.35.21 
appears twice, once titled “FAN AND TORQUATROL UNIT (Early Cars)” and then titled “FAN AND 
TORQUATROL UNIT (Later Cars)”.  The diagrams and text for these sections appear to be transposed, as the section 
for “later cars” matches my 1975 car (as well as the illustration in the 1980 edition of the parts catalogue).” 

On second thought, maybe not.  Morrin continues: “I am now sure that the version with the 4 bolts holding the clutch 
on to the pulley is the early version used on the carburetted XJ12 (and never on the XJ-S), as I now have one of these 
(XJ12) engines with fan clutch.  My “spare” 1973 XJ12 engine has a fan clutch with 4 bolts holding the clutch to the 
pulley.  The clutch has “HOLSET HUDDERSFIELD” cast on the front of it.  The illustrations both clearly show metal 
fans.” 

So, apparently, this is what we have:  The early XJ12 had a 4-bolt fan clutch with a metal fan.  When the XJ-S was 
introduced, it came with a 1-bolt fan clutch and a metal fan.  In 1979, this was replaced with a 4-bolt fan clutch with a 
plastic fan. 

There are photos of the guts of a 1-bolt fan clutch at: 

 

http://www.jag-lovers.org/xj-s/book/FanClutch1.html

 

And there are photos of the guts of a 4-bolt fan clutch at: 

 

http://www.jag-lovers.org/xj-s/book/FanClutch.html

 

 

OPERATION -- 1-BOLT CLUTCH:  The 1-bolt fan clutch is a study in simplicity; the hub that is bolted to the pulley 
is a simple disk inside an aluminum housing filled with thick goo.  There aren’t even any bearings; the disk itself serves 
as a goo-lubricated bearing. 

 

FAN CLUTCH CHECKING -- 1-BOLT CLUTCH:    It would appear that the only plausible failure mode would be 
for one of the seals to fail and the goo to escape, and there are reports of such failures; the goo leaves a track on the 
outside of the clutch and perhaps spattered around the engine compartment.  Such a failure should be apparent when 
turning the fan by hand; either the resistance is “jerky” or inconsistent, indicating some of the goo is gone, or it spins 
effortlessly, indicating all of the goo is gone.