I know there was a thread once about the issues of breaking
a plug and bits falling into the combustion chamber, but I
cant find it.
So, I cracked a plug a while back, bits fell into the spark
plug hole. A thread was created to determine the
consequences. I believe the response was ‘it’s ok’ and not
to worry about it.
Reviewing the notes from the motor dis-assembly the cylinder
liner that the plug problem happened to was heavily scored
and discarded. It was actually the worst liner.
In reply to a message from Repairman sent Mon 29 Jul 2013:
I can’t imagine ceramic could be good in the chamber…but I do
imagine that it blew out pretty quickly after doing its damage.
Until I worked on the XJS, I only broke a couple plugs
removing/installing my whole life. On this car I end up breaking 3
or 4 on every plug change, so I believe this is a common issue.
After I loosen all 12 plugs, I use a shop vac, air hose, and mirror
before removing them.–
John. '95 XJS 6.0L convertible. Southlake, TX
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That’s very interesting. I have never, ever, broken a spark plug while
working on any of our family cars (Jaguar and non-Jaguar) in 40 plus years
of DIY auto maintenance including work on our two 5.3L V12 Jaguars. I did
have stripped plug threads on the head in one XK engine head which was
repaired with a helicoil. You break 3 or 4 every plug change?
Regards,
Paul M. Novak
1990 Series III V12 Vanden Plas
1990 XJ-S Classic Collection convertible
1987 XJ6 Vanden Plas
1984 XJ6 Vanden Plas
1969 E-Type FHC
1957 MK VIII Saloon
Ramona, CA
P.M.Novak7@gmail.com-----Original Message-----
From: owner-xj-s@jag-lovers.org [mailto:owner-xj-s@jag-lovers.org] On Behalf
Of CJ95
Sent: Tuesday, July 30, 2013 6:00 AM
To: xj-s@jag-lovers.org
Subject: Re: [xj-s] Broken plug ceramic in the combustion chamber
In reply to a message from Repairman sent Mon 29 Jul 2013:
On this car I end up breaking 3 or 4 on every plug change, so I believe this
is a common issue.
After I loosen all 12 plugs, I use a shop vac, air hose, and mirror before
removing them.
In reply to a message from Paul M. Novak sent Tue 30 Jul 2013:
What can I say? I’m a brute mechanic. But, I didn’t make
the thread, so I’m not the only one who has broken a plug.–
John. '95 XJS 6.0L convertible. Southlake, TX
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In reply to a message from CJ95 sent Tue 30 Jul 2013:
CJ95
You are not alone. I cracked a few, which is easily done.
So check this out:
When I took my motor apart, the plugs were removed and
examined. Four of them had cracked internally but had no
visible (to my eyes) cracks externally. I know this because
they cracked upon removal and the center core of each plug
was rusted. If you crack a fresh plug, the core is shiny
My conclusion about breaking a plug is that you had better
make sure everything is removed from the cylinder or kiss
that cylinder goodbye.
Cheers–
The original message included these comments:
What can I say? I’m a brute mechanic. But, I didn’t make
the thread, so I’m not the only one who has broken a plug.
In reply to a message from Repairman sent Wed 31 Jul 2013:
Wow. I have to assume that nobody is klutzy enough to
have dropped all 4 plugs, so you may want to make sure you
are not getting detonation. Not sure how else they could
crack internally.–
The original message included these comments:
examined. Four of them had cracked internally but had no
You are not alone. I cracked a few, which is easily done.
Is this an HE-only issue? I’ve R/R my plugs myself every 2 years or more
often since 1999 and never broken a plug. Don’t even understand how it could
happen.
In reply to a message from Ed Sowell sent Wed 31 Jul 2013:
It’s easy Ed, just let me come and work on your car !
Could be an HE issue with the angled plugs
If you have the plug socket at the wrong angle(easily done)
and tighten, you can crack the plug, easier than you think.
The plug may not be physically in two pieces, but it is cracked.
As I said earlier, IF you do crack one, split it, look at
the electrode inside and see if its rusted.
On the other hand I can’t believe I’m the only one out there
that can screw plugs up, other than CJ95. My mother always
said I was special, but not THAT special.
I suspect at lot of owners are driving with cracked plugs.
Remember: Denial is not just a river
Cheers–
The original message included these comments:
Is this an HE-only issue? I’ve R/R my plugs myself every 2 years or more
often since 1999 and never broken a plug. Don’t even understand how it could
happen.
It’s easy Ed, just let me come and work on your car !
OK, you can be the under-the-car tech. Not much down there you might bust!
If you have the plug socket at the wrong angle(easily done) and tighten,
you can crack the plug, easier than you think.
Then that’s probably the reason it’s happening on the HE’s and not the
PreHE’s. There’s no problem getting the socket on straight for the PreHE.
But here’s another thought. My plug socket has a rubber insert that fits
over the plug porcelain. Does yours? It acts as a guide. Another thing it
does is hold on to the plug so it’s lifted out by the socket. Downside is
after the plug is installed and you pull up on the extension the socket most
often stays on the plug. I have to use my long-nosed pliers to pull it off.
In reply to a message from Ed Sowell sent Thu 1 Aug 2013:
My first thought was that the piston would smash the ceramic and
the compression would spit it out the exhaust with no harm.
Well, mebbe not! Bits might get into the ring grooves and raise
h… An abrasive so to speak.
Back in time to when I was young!!!
When I junk raced, some real t… poured bits of broken files and
other stuff in t the open carbs of a racer. P… off because the
car was much too fast for him and the driver much better. Hoppy was
the victim. A former flat track motorcycle racer. Wanna gusee the
genesis of his name?
Years later, I acquired a derelict 40 Ford Pickup. it was sans
engine and trans and had a smashed right front fender, the resuot
of a badly leaking brake system. It’s really ggod engione and trans
retained by the PO. The friendly junk man gave me a 53 Mercury
engine, health in question. Supposedly had a knock and as such was
scrap iron. I took it home and removed the heads. SOB, the brass
tip of a spark plug had raised h… in one hole. The tips were
removeable at that time!!And, some scary cracks from cylinder to
valve ports!!! An old time mechanic, now garage owner showed me how
to stich the cracks. He also used his old Ford special tool to
break the guides loose on the valves so I could do a valve job. A
new piston, set of rings, valve job and it ran great. I made a
transmission from a collection of blown ones at the friendly junk
man. Again from the scrap iron heap. I did buy a used radiator from
him. When messing with fixing the leaky braes I found the front
axle bent!! part of the crushed fender episode. With a bottle jack
and chain, I pulled it straight!!! I got s front clip from a guy
that rolled his 40 sedan. Supposedly, they are close but don’t fit.
I put the fenders on just fine and my hood was fine. Sold the hood
for the price I paid for the clip!
If one necks down the suction side of a shop vac, one can pull
debris out of a cylinder with no need to pull the head.
Carl–
Carl Hutchins 1983 Jaguar XJ6 with LT1 and 1994 Jeep Grand
Walnut Creek, California, United States
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In reply to a message from Ed Sowell sent Wed 31 Jul 2013:
I’m with you, Ed. I have changed at least a couple
thousand plugs over the years, and only broke a couple
till I worked on this thing.
The angles have you working around the AC compressor,
through the huge distributor, under and around the fuel
rail, and past the oil press sender. You end up using box
wrenches, deep sockets, different length extensions, and
universal joints…a different combination for many plugs,
so you can’t get in a rhythm. Combine that with the fact
that you can’t really see the plugs on the side of the car
you are working on…your reaching around the air rail,
fuel rail, and intake runners, and guessing at the angle
of the plug.
I usually snap them when I am breaking them loose taking
out the old plugs. Even with anti seize, it takes a good
bit of torque to pop them loose, and if you are twisting
at even a slight angle the porcelain pops with it.
Much easier to snap them than you would think…–
The original message included these comments:
often since 1999 and never broken a plug. Don’t even understand how it could
happen.
In reply to a message from CJ95 sent Mon 5 Aug 2013:
CJ95:
Agree the HE plugs are a bugger to get at.
But, with anti-seize and no more than 8 ft lb of torque on
installation, you should not have THAT much trouble pulling them.
Were any cross-threaded before?
In reply to a message from mike90 sent Mon 5 Aug 2013:
They are no trouble at all to remove. It’s also no
trouble at all cracking the porcelain. It’s rather funny
specifying an exact torque, as there is no way to put a
torque wrench on more than half the plugs.–
The original message included these comments:
installation, you should not have THAT much trouble pulling them.
Below you said that "there is no way to put a torque wrench on more
than half the plugs".
When I got our 1990 XJ-S convertible (5.3L V12 w/ Marelli
ignition) in 2005 I removed the spark plug wires, cruise control bellows
assembly, fuel rail with injectors, throttle pedestal, coils, and unbolted
the A/C compressor and moved it forward (not disconnecting any of the A/C
hoses) as described in Kirby’s book. This gave me clear and unrestricted
access to all 12 of the spark plugs when I did a compression check,
changed all the plugs, and cleaned out the entire “V”. At the time I had
full access to each of the spark plugs and used a torque wrench to tighten
them all up to spec (after putting some anti-seize on the threads) without
needing any complicated swivels or extenders. Granted that this took a
while to do and it was not quick nor easy. However, spark plugs do not
need to be changed very often, so it was well worth the effort. Not a
single spark plug was broken this time, or any other time I have worked on
any of my Jaguars.
I don't own a 6.0L equipped Jaguar, but I can't imagine that
it’s that much different.
Regards,
Paul M. Novak
1990 Series III V12 Vanden Plas
1990 XJ-S Classic Collection convertible
1987 XJ6 Vanden Plas
1984 XJ6 Vanden Plas
1969 E-Type FHC
1957 MK VIII Saloon
Ramona, CA
P.M.Novak7@gmail.com-----Original Message-----
From: owner-xj-s@jag-lovers.org [mailto:owner-xj-s@jag-lovers.org] On Behalf
Of CJ95
Sent: Tuesday, August 06, 2013 8:08 AM
To: xj-s@jag-lovers.org
Subject: RE: [xj-s] Broken plug ceramic in the combustion chamber
In reply to a message from mike90 sent Mon 5 Aug 2013:
They are no trouble at all to remove. It’s also no trouble at all cracking
the porcelain. It’s rather funny specifying an exact torque, as there is no
way to put a torque wrench on more than half the plugs.
The original message included these comments:
installation, you should not have THAT much trouble pulling them.
In reply to a message from CJ95 sent Tue 6 Aug 2013:
CJ95:
Funny!
I don’t have any problem getting a torque wrench on mine, however,
on my car, I don’t have:
cruise control bellows
air rail, and associated hardware
A/C compressor and related plumbing
My car is a convertible, and I have no need of A/C. The rest of
the stuff was removed to clean up the ‘V’, and reduce some weight.
It still takes a while to do (changed 3 sets in one month last
year, chasing an overfueling problem that fouled the plugs in short
order), but I can pretty much have at it.
Those unfortunate souls who must contend with the extra hardware
must lose hair each time they must refresh the plugs.
-M–
The original message included these comments:
Well, I’ll just let you come do mine next time. I change
them twice a year.
In reply to a message from Kirbert sent Tue 6 Aug 2013:
I knew that would draw fire!
I pull them once to sand blast and inspect before the
annual inspection…in hope that it will pass. It never
does pass the emmision test, so I pull and replace them
after the first inspection prior to the recheck. (this
has been covered a couple times in my prior threads)
I could pull the compressor and oil sender to replace
them, but what’s the point? I can do the whole job in 30
minutes and only loose 3 or 4 old plugs I was going to
trash anyway. Removing and replacing the compressor alone
would take twice that long…to save junk plugs. Not to
mention that any time you start yanking on 20 year old AC
pipes and lines there is a chance of loosing one. Just
not worth it to save a few junk plugs…or to actually get
a torque wrench on the end plugs.
Here in Texas it has been over 100 degrees all week. I
once tried to go without AC. With the windows down, your
eyeballs dry out and stick to your eyelids on the freeway.
If you roll the windows up, your sweat drips down into
your eyes and burns. Either way you can’t see. I
promptly fixed the AC!–
The original message included these comments:
In reply to a message from CJ95 sent Wed 7 Aug 2013:
John:
I grew up in West Texas. No AC then. Swamp coolers here and there.
We managed. Would I do it now, No way!!
Agree, saving old plugs is, kinda nutty!! Although, I do have one
of those little sand blast cleaners for them!! I’ve used it with
good effect on my one lung garden engines.
Carl–
The original message included these comments:
Here in Texas it has been over 100 degrees all week. I
once tried to go without AC. With the windows down, your
eyeballs dry out and stick to your eyelids on the freeway.
If you roll the windows up, your sweat drips down into
your eyes and burns. Either way you can’t see. I
promptly fixed the AC!