With ( presumably ) steel spark plugs in an aluminium alloy head, is it better to try to unscrew them with the head hot, or cold ? ( Thinking about differential expansion )
I would do it all cold as when you put them back in an torque them up you should get the setting right
I've removed and re-fitted them hot and cold many times and not had any issues.
Don't forget anti-seize when you install, and try not to use the copper stuff.
If the plugs are tight removing them with head hot can help.
I put them in cold with a dab of copper grease on the threads.
I think ngk specify not use and grease or anything
quote:
I think ngk specify not use and grease or anything
quote:
Originally posted by designer
quote:
I think ngk specify not use and grease or anything
Alloy + steel + heat = galvanic corrosion
I think the use of grease can cause they to be overtightened. I never bother with copper grease but tighten with a torque wrench and never had any issues.
quote:
Originally posted by r1_pete
quote:
Originally posted by designer
quote:
I think ngk specify not use and grease or anything
Alloy + steel + heat = galvanic corrosion
Agree I've been using a little copper grease for years, on cars and bikes, never had a running issue, or an unmovable plug.
I always put on copper grease. I've only once had my car serviced by a garage, and when I came to do the next service I couldnt get one of the
plugs out (Honda VTEC). Tried hot, cold, release spray, that freezing stuff on etc etc, and eventually ended up snapping the plug and having to take
the head off and have it drilled out. The garage didnt use copper grease "because it doesn't make any difference".
Regards
Hugh
Many thanks
Erm..NGK's were the(?) first plug maker to nickel plate their plug threads for the purpose of eliminating Steel/ali corrosion and ultimate
seizing.
Typically these Do Not need anti seize on their threads .. Although I still do it out of pure cowardice after having a set of Champion plugs (those
were NOT nickel plated) Seize in my XK120 Ended up putting Threadserts into that Cyl head as result.
Moral being: IF your plugs do seize, spark plug hole damage is inevitable.
Like revenge best done cold but hot is not generally a problem
Tip (1) never use copperslip it actually causes aluminium alloy components to seize on ----
Tip (2) If your plug socket has an internal rubber sleeve extract it throw it to b****** otherwise you will tend to break plugs. With deeply
recessed plugs you pull the plugs out with a bit of rubber hose or a plug lead.
Tip (3) Some engines with tapered seat plugs especially Ford Valencia (Fiesta OVH) and BL O series are very prone to plugs shearing off
--- take care.
Tip (4) always screw plugs in by hand, if you even slightly suspect the plug is started on the wrong thread unscrewand try again, if still not
screwing straight use a plug thread repair chaser tap.
Champion plugs in VW aircooloed vengine tend to sieze in the heads whereas I've never had the problem with NGKs . Thrashing Vws to get the engine as hot as possible sometimes helps when removing so I would say hot
We use NGK sparkplugs on our V2500 IAE engine (Airbus A321) and the manuals recommend anti-seize, albeit it a much higher operating temperature. A little lube never hurts as much as no lube ;-)
Re Coppaslip and aluminium they are not compatible due to bi-metal corrosion, for alloy wheels best practice is to use an aluminium or aluminium
& zinc or Aluminium and Graphite based anti-seize compound.
Landrover had major problem with seized on alloy wheels until they issued strict instructions to use Zeta anti-seize compound not copper
based.
If you search ebay on "anti-seize aluminium " it should turn up various alternative types.
quote:
Originally posted by Bare
Moral being: IF your plugs do seize, spark plug hole damage is inevitable.
quote:
Originally posted by nick205
I've removed and re-fitted them hot and cold many times and not had any issues.
quote:
Originally posted by britishtrident
Tip (3) Some engines with tapered seat plugs especially Ford Valencia (Fiesta OVH) and BL O series are very prone to plugs shearing off --- take care.
