Everything was fine with my 1983 until suddenly it started missing and clicking

I finally got my 1983 xj-6 on the road for a road test. Everything run fine and dandy, then when the car got up to operating temperature, piston set 1, the piston set nearest to the front of the car starting clattering–essentially a metal, mechanical sound. I pulled the spark plug on the piston/valve set and at looked carbon dirty–just changed the plugs a few miles ago. I cleaned and re-gaped the spark plug and re-installed it. the miss stopped but the clattering continued, Now that engine has 127 K miles on it, but most all highway miles, and oil changes every 2 k miles. Car was impeccably maintained, though sat in a garage for 3 years when I bought it. My friend who works on this car with me feels it is a serious valve problem, but I feel it just may be a sticky lifter or something more minor–perhaps wishful thinking on my part. Anyway, anyone out there have any thoughts on this subject?
Chris

Tappet bucket loose? If it was a sticking valve it would have possibly collided with the piston by now.

Thank you for your response, Robin. Do you know the fix?
Chris

Depending how mechanically minded you areSome of the usuals may have stake down kits available, otherwise a plate can be drilled with a clearance hole and the head is tapped between two valves. The plate should just nip the edges of the adjacent buckets. If you google Jaguar tappet bucket stake downs and go to images you will see what I mean.

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Tappet guide ‘rising’, as Robin imply, is certainly a possibility, Chris. You don’t mention whether it is the inlet or exhaust side - remove camshaft cover as appropriate and inspect tappet guide. Compare to the other tappet guides, #1 should be at same level as the others - and undamaged. If either; unless guide is very damaged, a ‘stakedown’, as Robin describes, is a an appropriate and effective solution…

You may prefer to run a simple compression test first; if a piston is hitting the valve; the valve is bent - and you have little or no compression in #1 compared to the others. .A bent valve requires head removal - but if nothing; proceed to tappet guide However; #1 is up front and the noise might be cam chains chattering - try better location of noise?

As an aside; changing oil every 2000 miles is a bit overkill - unless done once a year…:slight_smile:

Frank
xj6 85 Sov Europe (UK/NZ)
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Thanks very much for this info, Frank. I also thought that a compression
test would be the next step. And I will proceed with that and see what
happens. I was given two Jags, a 83 xj-6, and a 87 XJ-6 from a friend in
his will. I’d rather have my friend than the Jaguars, but I really want to
make these cars work.He was my best friend who 30 years ago we met in our
local Jaguar club. He had a 1972 E type roadster and I had a 1969 E type
coupe. Those were the days when they were relatively inexpensive. Both of
these xj-6s’ were in storage for 3 years so I have my hands full… Thanks
again, Frank.
Chris

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Chris,

you don’t mention where you’re located - the catalysed versions of the XK engine (i.e. US spec) seem to be particularly prone to the tappet guide thing on the exhaust side. Before pulling the cam covers you might want to examine through the oil filler cap. First and foremost, you can easily see whether the stakedown kit has already been installed. Secondly, you might even see - and if just with a mirror and a light - whether the front exhaust valve guide ( # 6 in Jag terminology) looks different than #5 or #4.

To test for a bent valve and assumedly lost compression on #6 you can try and pull the HT wires. If a cylinder is doing serious work, pulling the wire usually results in immediate changes of the engine’s operation. If the cylinder does not contribute to the engine’s work - as caused in the event of a loss of compression - there is hardly any noticeable change.

Good luck

Jochen

75 XJ6L 4.2 auto (UK spec)

Jochen,
Thank you very much for your response and information. My 83 XJ-6 is an American Spec., actually a California Spec. car brought out to Colorado where I live. I assume the exhaust valves are on the left side of the engine facing forward…yes? Also, I pulled a spark plug on the suspicious piston/valve set (first piston set foremost to the front of the car because there seemed to be a miss there. I cleaned and re-gaped the spark plug and the misfire went away. Is this a normal occurrence with a loose tappet? Anyway I will do as you suggested in your email and hope that ii is indeed just a loose tappet and a stake down kit will do, rather than a valve job. Thanks again, Jochen.
Chris

As a final note, do post your findings.
It helps others …

Nothing personal, however it does bother me how people pop in for info then disappearing without response or resolution for others.
It’s just polite.

FWIW

So remove cam covers and inspect for any tappet damage or strangeness.
do a search as it is well covered. Check front timing chain while there.

If nothing to be seen, perform compression test.
Should be about 150-160 … but with your mileage expect less.

If nothing thus far it would be a surprise…

Thank you Demian, for this info and for all the help and patience you have
given. This Saturday, I am going to have some time and do what you and
others have suggested. Thanks again, Demian
Chris

Hoping for the best for ya…I know how that is and how frustrating it can be tracing noises.

Remember to check those gaps between shims and tappets, at least a bit as too large a gap can cause the cam to smack them down creating such noises…

In time the upside down bucket tappets will be smashed by the cam and metal pieces go into engine. Not good…

Best wishes…these things are tricky to trace…

Thank you Demian. My friend and I (my friend being much more mechanical) are going to see what’s really going on with my 83. Also, we’re going to diagnose problems with the 87. I don’t see that well up close any more, so my friend, Pat, has better eyesight and a better mechanic. I’m rather curious on the status of your S1 Sj-6? How’s that going?
Chris

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Apart from the eyesight, Chris - a second opinion is always worth while…

Frank
xj6 85 Sov Europe (UK/NZ)
**

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YUP!!!

Agree, a version of the old saw, “two heads are better than one”.

From time to time, my neighbor and I do that. "come over here and have a look at this:, He and his brother are far younger than I
Their ears are far better…

My eyes are , still, Ok, but, at times, in addition to my spec’s I find a magnifying glass helpful.

Carl

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Thanks for the responses.
Chris