[xj-s] HELP! Don't know what this loud Tapping sound is HELP!

I just purchased a XJS V12 approx a 77 model it has a very
loud tapping noise from the left bank and also blows blue
smoke from the left hand side the last owner told me the car
had been sitting for a good few months and the noise was not
there before he parked it, after sitting so long he started
it and the noise was there it comes and goes every couple of
seconds very strange the previous owner was told by a
machanic to give it a good rev up the road but he would not
do this, The funny thing is, my brother has just got him
self one as well same model V12 it does the same thing only
from the right hand side and blows blue smoke from the right
and it also hase been sitting for several months and the
previous owner said the same thing, that it was not there
before, so if anyone can help with this problem that would
be fantastic.

Regards George.–
George Simpson
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

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George, both you and your brother should do compression tests on your
engines. The aluminum heads have steel valve seat inserts and, usually
after severe overheating, one or more seats will pop out of the head. The
result is a loud clacking noise from the offending bank, and smoke from
incomplete combustion and oil leaking into the bad cylinder(s). Compression
(and leak-down) tests will verify one or more weak cylinders, if the
problems are dropped valve seat.

Jim Johnson - NCJOC
'88 XJ-S, V12, Lucas (CEI), TH400 (w/B&M), Dana 2.87
Annapolis, Maryland

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