[xj40] Removing cylinder head

Dear all,
My owners manual suggests I remove the bonnet (hood) as a
first stage to removing the cylinder head. Is this
absolutely necessary? Is it also necessary to remove the
cams from the head also. I was planning to set everything
to TDC, mark accordingly and remove the upper timing chain
by unbolting the sprockets from the cams. Am I missing
something here? The head gasket seems due for replacement
and I don’t see the need to mess about with the cams. All
advice very welcome!
PerErs. XJ40 (1990) 4.0 litre. Manual.–
XJ 4,2 coupe 1977. XJ 40 1990.
Stockholm, Sweden
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In reply to a message from Perers sent Mon 1 Apr 2013:

It is certainly not essential to remove the bonnet when
removing the cylinder head - but it obviously does give
better access if you do. I did remove the bonnet when I
replaced the head gasket on my car, but you need at least
one other helper to hold it in position while you remove or
replace the hinge bolts - and it is heavy!!

Whilst it is equally not essential to remove the camshafts
in order to replace the head gasket, I am surprised that you
are doing that amount of work without removing and cleaning
up the valves and, since yours is a '90 model which never
had them fitted in new build, fitting exhaust valve stem
seals and replacing the inlet valve stem seals too.

BTW, after removing the camshaft sprockets do not rotate the
camshafts with the heads on or off the block, otherwise you
will probably bend one or more of the valves. This is an
‘interference’ engine.

If you do remove the camshafts, note that the inlet and
exhaust, although they look the same are not! :-)–
The original message included these comments:

My owners manual suggests I remove the bonnet (hood) as a
first stage to removing the cylinder head. Is this
absolutely necessary? Is it also necessary to remove the
cams from the head also. I was planning to set everything
to TDC, mark accordingly and remove the upper timing chain
by unbolting the sprockets from the cams. Am I missing
something here? The head gasket seems due for replacement
and I don’t see the need to mess about with the cams. All
advice very welcome!


Bryan N, '91 Sovereign 4.0 L, RHD
Cambridgeshire, United Kingdom
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In reply to a message from Bryan N sent Mon 1 Apr 2013:

Thank you Bryan,
I have suspected potential cylinder head failure as
anytime soon ( classic oil and water mix evident in the
oil filler tube). The clincher the last few outings for
the car was a slight but persistent oil leak which was
burning on hot areas and producing smoke. The valve info
is very handy to know but time us of the essence as I am
now relying on my xj coupe to get around and I’d much
rather have my lovely 40 back on the road as it copes with
this prolonged winter much much better.
Thanks again!–
XJ 4,2 coupe 1977. XJ 40 1990.
Stockholm, Sweden
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In reply to a message from Perers sent Mon 1 Apr 2013:

I made up two flat metal links that were longer than the
gas-filled struts that allowed the bonnet to stand vertical,
giving lots of room to maneuver. I removed the intake
manifold completely, and that opened a place to stand
straddling the engine. I lifted the head off and moved it
onto the well-padded right fender, then lifted it off the
fender. I did it without help that way.
The head bolts run through the cam bearing caps, so you may
as well remove the cams since they’ll be loose.
While you have the head off, you may want to replace the
valve stem seals, especially if you get a puff of blue smoke
at the first start of the day.–
The original message included these comments:

My owners manual suggests I remove the bonnet (hood) as a
first stage to removing the cylinder head. Is this
absolutely necessary? Is it also necessary to remove the
cams from the head also. I was planning to set everything
to TDC, mark accordingly and remove the upper timing chain
by unbolting the sprockets from the cams. Am I missing
something here? The head gasket seems due for replacement
and I don’t see the need to mess about with the cams. All
advice very welcome!


Pete Peterson 70E(193K) XJ40s(88-270K,89-97K, 94-122K)
Severna Park, Maryland, United States
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In reply to a message from Perers sent Mon 1 Apr 2013:

Hi,
If your car is not overheating or actually constantly
losing coolant, the head gasket could be fine and doing it’s
job perfectly.

The oil/water mix, or mayonaise like stuff in the oil
filler tube is not necessarily a sign of head gasket failure.

I had the same creamy oil/ water mix forming in the filler
tube on my Sovereign for more than 86,000 miles of ownership
and the head gasket was perfect throughout that time, with
no coolant loss or ever a sign of overheating.
The Jaguar specialist I consulted said it was a sign the
oil was doing it’s job properly and not to worry.

At some oil changes there would be very little sign of it,
and at others it would be almost blocking the filler tube.
I used to use a slim spoon taped to a stick to scoop it out
at each oil change.

Oil can leak from many places near the top of the engine too.

I’m just thinking that having read the ‘history’ about xj40
head gaskets,then seeing the oil/water in the filler tube,
you might be jumping to the wrong conclusion and performing
a lot of work that might not be necessary.
good luck.–
The original message included these comments:

I have suspected potential cylinder head failure as
anytime soon ( classic oil and water mix evident in the
oil filler tube). The clincher the last few outings for
the car was a slight but persistent oil leak which was
burning on hot areas and producing smoke. The valve info
is very handy to know but time us of the essence as I am
rather have my lovely 40 back on the road as it copes with


Casso - 1993 Jaguarsport XJR 4.0 A.
Liverpool, United Kingdom
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In reply to a message from Perers sent Mon 1 Apr 2013:

When you remove the head there are two little jobs that are very
easy to do and will save you a lot of pain later. replace the hose
that run under the inlet manifold from the pump to the block and
replace the orings on the oil cooler connection to the block just
under the the oil filter. Twenty minutes will do these jobs when
the head is off, when its back on it could take two or three hours.
Good luck. John–
John. Walsh. Purrrrr 89 vdp
bowmanville ontario, Canada
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In reply to a message from Casso sent Mon 1 Apr 2013:

I agree. The mayonnaise like stuff in the filler tube is
expected – it’s normal water condensate mixed with
detergent additives in the oil. I’ve got it in both of my
88s and my 89. My 94 has the filler cap in the cam cover
itself so it doesn’t develop the mayonnaise.
An oil leak generally develops when the cam cover gasket
gets hard and the screws loosen slightly, allowing a drip
from the right rear corner down onto the catalytic
converter. I’d replace that gasket first before tearing the
head off.–
The original message included these comments:

The oil/water mix, or mayonaise like stuff in the oil
filler tube is not necessarily a sign of head gasket failure.
I had the same creamy oil/ water mix forming in the filler
tube on my Sovereign for more than 86,000 miles of ownership
and the head gasket was perfect throughout that time, with
no coolant loss or ever a sign of overheating.
I’m just thinking that having read the ‘history’ about xj40
head gaskets,then seeing the oil/water in the filler tube,
you might be jumping to the wrong conclusion and performing
a lot of work that might not be necessary.


Pete Peterson 70E(193K) XJ40s(88-270K,89-97K, 94-122K)
Severna Park, Maryland, United States
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Hi All. Just my 2c worth.
The mayonnaise generally is indicative of short runs where the engine is not
getting up to temperature for a long enough period to dry out the
condensation that collects in the engine.
Not sure if this is the case in this instance perhaps you can advise if the
car has been on any long runs recently?
I would concur with the other replies, carry out a compression check and/or
a leak down test or a ’ Block Check’ (gases in the coolant) to see if there
are any mechanical sugggestions that point to a head gasket failure.

or
http://www.blockchek.com/store.htm

Regards Robin O’Connor
'92 XJ40 4.0 Ltr
Auckland NZ----- Original Message -----
From: “Jaguarpete” jaguarpete@aol.com
To: xj40@jag-lovers.org
Sent: Tuesday, April 02, 2013 8:24 AM
Subject: Re: [xj40] Removing cylinder head

In reply to a message from Casso sent Mon 1 Apr 2013:

I agree. The mayonnaise like stuff in the filler tube is
expected – it’s normal water condensate mixed with
detergent additives in the oil. I’ve got it in both of my
88s and my 89. My 94 has the filler cap in the cam cover
itself so it doesn’t develop the mayonnaise.
An oil leak generally develops when the cam cover gasket


Pete Peterson 70E(193K) XJ40s(88-270K,89-97K, 94-122K)
Severna Park, Maryland, United States
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Line Books and more !

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In reply to a message from Perers sent Mon 1 Apr 2013:

Having just completed the task of replacing the head gasket
on my '94 VDP I can say for me that I would not want to do
that job with the bonnet on. It only takes a few minutes to
remove and replace but well worth the time for the increased
access. It does however require two people.–
The original message included these comments:

My owners manual suggests I remove the bonnet (hood) as a
first stage to removing the cylinder head. Is this
absolutely necessary? Is it also necessary to remove the


Joe Umbertino ~ 1986 XJ6 / 1994 VDP 4.0L
Mesa, AZ, United States
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I agree - removing the hood (bonnet) is not a big deal and it improves the access immensely, especially if you are going to remove the radiator to give it a thorough cleaning, replace the rubber mounts, and de-rust and paint the lower radiator support / cross-member.

Mike Stone
1994 XJ6/XJ40
161,XXX miles
Springfield, Missouri USASent via Palm Centro� “Yesterday’s Technology Today”

-----Original Message-----

From: “Jag.Man” joeu@q.com
Subj: Re: [xj40] Removing cylinder head
Date: Mon Apr 1, 2013 4:29 pm
Size: 938 bytes
To: xj40@jag-lovers.org

In reply to a message from Perers sent Mon 1 Apr 2013:

Having just completed the task of replacing the head gasket
on my '94 VDP I can say for me that I would not want to do
that job with the bonnet on. It only takes a few minutes to
remove and replace but well worth the time for the increased
access. It does however require two people.

The original message included these comments:

My owners manual suggests I remove the bonnet (hood) as a
first stage to removing the cylinder head. Is this
absolutely necessary? Is it also necessary to remove the


Joe Umbertino ~ 1986 XJ6 / 1994 VDP 4.0L
Mesa, AZ, United States
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In reply to a message from Perers sent Mon 1 Apr 2013:

Perers,

I agree that the gunk you note in the oil filler tube is
100% normal for Jaguar XJ40s and is not indicative of a head
gasket problem. Oil ‘‘burning on hot areas’’ may simply mean
the cam cover gasket has cracked and oil is leaking onto the
exhaust manifold: another common issue on the XJ40 since the
engine is tilted toward the exhaust.

You don’t mention the mileage on your engine, but we’ll
assume it is getting up there, so there are no reasons not
to replace the head gasket preemptively aside from the cost
of the parts and the time involved. If you decide to
proceed, here are a few thoughts in addition to those
offered by others:

I have done XJ40 head gaskets three times and have never
removed the hood. It simply hasn’t been an issue for me.

I remove the air intake plumbing and throttle body and
disconnect the intake manifold and tie it back toward the
left fender but do not removed it entirely.

Before you loosen the head bolts, measure the valve
clearances and take careful notes for each valve. Later, as
you remove the valves to add stem seals, record the shim
thicknesses for each tappet. With this info you can
determine the new shims needed.

To remove the head by myself, I pad the right fender like
Pete, then I sit on the windshield (carefully) straddling
the engine. I lift the head up and over to the thick
padding on the right fender, then climb off the left side of
the car. I haven’t broken a windshield yet…

While the head is off, replace ALL the coolant hoses under
the intake manifold, the breather hose from the cam cover to
the oil filler tube, the silicone sealant on the water rail,
the O-rings on the oil cooler pipes or
cooler-bypass-fitting, the oil filter housing gaskets (or
silicone sealant if no gaskets are present), the silicone
sealant on the oil filler tube housing (the rubber bush that
seals the oil fill tube is no longer available from Jaguar
so be careful not to break it), the rubber sleeve at the
bottom of the oil dip stick tube (still available from
Jaguar but it’s just a piece of rubber tubing), the vacuum
hoses that are impossible to access when the intake manifold
is in place, and the hoses from the carbon canister purge
valve to the intake manifold and from the carbon canister
vacuum control valve to the fuel pressure regulator.

Seriously consider replacing the upper timing chain
tensioner blade, oil pressure sender and heater control
valve, and think long and hard about replacing the starter
since it will never be easier.

Lap/reseat the valves. It’s easy and only takes a cheap
suction cup lapping tool and some compound.

Clean the throttle body (see the archives for risks of
fouling the TPS with cleaning fluids). Clean the carbon
from the EGR port just inside the intake manifold. Clean
the MAF with MAF-specific cleaner spray. Use electrical
contact cleaner spray on all connectors and seal them with
dielectric grease.

Now, install the supercharger. (just kidding!)

Cheers, Don–
The original message included these comments:

I have suspected potential cylinder head failure as
anytime soon ( classic oil and water mix evident in the
oil filler tube). The clincher the last few outings for
the car was a slight but persistent oil leak which was
burning on hot areas and producing smoke. The valve info


Don B : '93 VDP Flamenco Red 189K : (ex-'88 Sovereign)
Franklin, TN, United States
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In reply to a message from Casso sent Mon 1 Apr 2013:

mine suffers the same, being the earlier seperate filler tube.
every winter is the same, with it filling up with creamy gunk. the
first year I had the car and saw this, I nearly had heart attack,
thinking head gasket, till it was pointed out that it was common on
my MY. every summer now, I remove the filler tube and wash it out.
so I would nt change a head gasket based on that. just keep the
filler tube as clean as you can and do a regular oil change!!–
The original message included these comments:

The oil/water mix, or mayonaise like stuff in the oil
filler tube is not necessarily a sign of head gasket failure.
I had the same creamy oil/ water mix forming in the filler
tube on my Sovereign for more than 86,000 miles of ownership
Casso - 1993 Jaguarsport XJR 4.0 A.
Liverpool, United Kingdom


SOVEREIGN 4.0L 1990
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In reply to a message from Casso sent Mon 1 Apr 2013:

Casso…along with all others have brought up good points…
Last year I went thru the same ordeal…the mayonnaise ‘‘effect’’ the
Gunk…The fear of Blown Head Gasket…

I thought for sure Head Gasket…Most people would of thought the
same, after seeing the inside of the Cam Cover…Mayonnaise Effect!!

But not to jump the gun…or give up…and think the worst… I ran
the car…looking for signs of over heating…etc

But NO!! not over Heating…But not heating up to normal operating
temperature…

That’s right…Engine running Cold…Would not heat up to the
proper temp range…

Replaced Thermostat…Now all of the Mayonnaise Effect Gone…

Seems the engine not up to temp…was causing
condensation…therfore giving it the Milky Effect…

So yes be sure it is the Head Gasket…

BTW…how many miles do you have on the clock?

Good Luck to you…

Cheers…Don–
The original message included these comments:

 If your car is not overheating or actually constantly

filler tube is not necessarily a sign of head gasket failure.
I had the same creamy oil/ water mix forming in the filler
no coolant loss or ever a sign of overheating.
I’m just thinking that having read the ‘history’ about xj40
head gaskets,then seeing the oil/water in the filler tube,
you might be jumping to the wrong conclusion and performing
a lot of work that might not be necessary.


Hello…Everyone… Don here 1988 XJ6 ok … Yes XJ40…:slight_smile:
Sacramento,CA, United States
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In reply to a message from DL Don sent Tue 2 Apr 2013:

Hello all,
Heaps of info here and thank you everyone. Previously I’d
made 120 km plus journeys with the car and fir about 6
months past only shorter 30 km runs. It would follow that
contribute to more condensation build up. Oh how I wished
I’d done a compression test first! That had even even on
my mind earlier. I had the new cam over gasket and semi
circular seals all set to swap when I had the stupid idea
to just check the tightness off the head bolts. The oil
leak really seemed not to be connected with the cam cover.
There was barely a trace of oil from we’re I had assumed
it would escape. This is a case of 2 and 2 makes five. I
went round the head bolts in sequence and found one to be
in need of tightening. Once tightened I found others in
the sequence in need of tightening. And so it went until
one if the bolts sheared. It must have been over stretched
or faulty. It was quite a shock! The head has to come off.
I bet I will still have the oil leak even after I get
through all of this. I am certain you’ll all be reading
this with disbelief! Ho hum. Back to it with a new set of
bolts and a gasket on order.–
XJ 4,2 coupe 1977. XJ 40 1990.
Stockholm, Sweden
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I recently changed the famous water pump to water rail hose which was leaking. The green coolant is bright and I don’t have any issues with temperature. I have also changed the thermostat lately. However, yesterday when I was changing the engine belts I noticed coolant on the bottom of the oil pan. All the coolant hoses seemed dry. I guess the leak is from the engine because the left rear side of the engine is wet. Any suggestions? :thinking:

The car drives well and the fuel consumption is good. However, idling is not super smooth, even if I have changed spark plugs, wires, rotor, distributor cap, fuel filter, fuel pump, oxygen sensor, air filter, and have had injection nozzles serviced professionally. I have also changed the valve cover seal and the spark plug O-rings. Mileage is 117000, MY 1989, 3.6.

Otto …

If you are losing coolant the first thing I would check are the hoses while they are under pressure with the engine running. If you suspect the leak is at the left rear of the engine of course that’s where the heater hoses and heater control valve are and where the water rail enters the block. So a lot of hoses and clamps. Double check that all the clamps are tight and look carefully for signs of leakage on the hoses in that area.

The very last thing I would suspect would be a failed head gasket allowing water to seep out of the engine. Much more common is a failure of the head gasket between a piston and a water gallery. In that case the piston will suck in the water. The water galleries are under so little pressure (less than 13 psi) I’ve never heard of a head gasket failing just from a gallery to the outside of the engine.

On a 31 year old engine the question is what doesn’t cause a rough idle, rather than what does. First step is to do a compression check or even better that and a leak down test. This will give you an excellent indication of the condition of the piston rings and valves. Until you’ve eliminated this as a problem you’re just chasing your tail. If the results are satisfactory then you can move on with your troubleshooting … removing and cleaning idle control valve, checking for vacuum leaks, checking cam clearances, etc, etc. I think you’ll find it’s rarely one big problem but rather several little things.

Dennis,

Based on different Jaguar forums, I got the impression that probably the leak is from the water rail gasket. However, I looked there and could not confirm this. But as you suggested, I have to check it when the engine is running.

A positive thing is that I managed to replace the engine belts. However, I noticed that I had broken plastic heads of the EAC 2630 thermal valve on the thermostat housing. Two vacuum lines are attached to these heads. However, I am not sure whether these vacuum lines are really necessary. :thinking:
[[v12-engine] EAC 2630 Thermal Valve]