I need to replace the spark plugs in a 1993 Volvo 850 GLT. Is there a conservative and safe rule of thumb I can use, such as "cold engine, finger tight, then add 1/8th turn", or do I have to go out and purchase a torque wrench?
Should I purchase some conductive anti-seize compound for the threads and non-conductive grease for the wire boots, or not bother?
Thanks in advance.
With aluminum alloy heads a torque wrench is highly recommended. NEVER put a spark plug into an alloy head without an approved antiseize compound. One can of it will last decades in most home garages (I still use a can of LeMans brand that i bought in about '81. The silicone dielectric grease on the inside of the boots where they mate with the plug helps keep moisture out and makes removal next time easier.
from Randy & Valerie __ __ \ \ / / \ \/ / \__/olvo 1993 960
I use copper-based antiseize on the threads, and tighten firmly; the only spec I've ever seen was in the 30-40 ft-lb range, so it's a bit more than 1/8 turn past finger tight. I don't use a torque wrench for plugs, though.
Dielectric grease for the boots won't hurt; they can develop a firm grip on the plugs. Usually, that can be broken by twisting the boot.
Gary
Also remember that if you swing on that wrench it is very easy to strip the threads in an aluminium head. Over tighten a little every time you change the plugs and the thread will eventually go.
Spark plugs are often the most over-tightend thing - there really is no need. They don't need more than moderate hand pressure. If in doubt, use the torque wrench.
Hi, Ted - - -
If you're going to do it with any regularity, *do* get yourself a torque wrench! The "20-40" foot pounds may cause grief sooner or later. If nothing else, the porcelain insulator in the plug is "hard, but not tough," ie: somewhat on the brittle side, so subject to fracture, and you don't want bits of porcelain dropping into the combustion chamber.
My '02 S60AWD looks for 22'# (30Nm), which I consider a bit high. The wife's '98 V70XC looks for 15-18'#. Anything more than what it takes to crush down the gasket is really plenty.
A *light* coat of anti-sieze is definitely in order. I think my 8oz. can of Permatex Commercial and Aircraft Grade is over 40 years old, so the comment about the stuff lasting is valid. The silicon lube is also a "forever" purchase and makes life a good bit easier.
bob noble Reno, NV, USA
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