ZX sparkplug removal

sponix · Unread post by **sponix** » 14 Jul 2004, 19:13

Time has come to replace the plugs on the ZX. It's the 1.4 that has recessed plugs in an aluminium head.
This is the first time we have removed the plugs from this car...any tips before proceeding? Is it worth, for example, soaking the things in WD40 a few weeks before we start? Should we remove the plugs with the head hot or cold? When replacing the plugs is it worth using copperease on the threads?

np · Unread post by np » 15 Jul 2004, 01:34

I`ve never had any probs changing plugs.I always change them after i`ve changed the oil,so the engine is warm.You should try changing then on a Saab 900 16V,there about 6 inches in the head.Just be carefull not to put to much strain on the ratchet when undoing/doing up,as you may cross thread the plug holes.Make sure you put them in straight and you should be alright.Also make sure the holes are nice and clean before removal.You dont want any muck falling into the holes.WD40 would proberly just burn off when the engine gets hot.I also wouldn`t put any copper grease on them when refitting.This is just from my own experience.Maybe somebody knows better???

meexi · Unread post by **meexi** » 15 Jul 2004, 03:58

instead of using the socket and ext bar to start the thread use a length of garden hose that way the pipe will spin if you start to cross thread it.
meexi

uhn113x · Unread post by **uhn113x** » 15 Jul 2004, 13:17

Hi sponix
My thoughts:
<ul><li>Neil is right - WD40 would 'proberly' just evaporate in half an hour</li>
<li>You should remove plugs in alloy heads when cold</li>
<li>I always put copper or nickel anti-seize on plug threads, especially in alloy heads. Remember, if the threads corrode together, you will remove small bits of head thread every time you take a plug out [:(]</li></ul>

sponix · Unread post by **sponix** » 15 Jul 2004, 18:44

What I'm worried about is the plugs being stuck in their respective threads. I have never had the plugs out on this car and don't know if the previous owner ever had them out or how much they were tightened..
So can I confirm the head on a 1.4 ZX *is* alloy (I haven't looked yet)
Good tip about the garden hose!
I'll try WD40 as a precaution as I suppose it won't do any harm. Hopefully if I do it a couple of times in the evening the WD40 may soak into the plug threads and make them come out easier.

Kowalski · Unread post by **Kowalski** » 15 Jul 2004, 20:51

WD40 won't get past the sealing washers, in fact the washers will keep the thread completely free of any WD40 you put down the holes. The WD40 will probably only lubricate the washers.
The copper/nickel in the anti-seize compound (e.g. copaslip) will stop galling (the head threads sticking to the plugs) but the oil/grease in it tends to end up carbonised on the threads because of the temperature. My experience has been that you should use the tiniest of smears on your plug threads because the carbon you can end up with can be more difficult to shift than just the galled threads.

sponix · Unread post by **sponix** » 23 Jul 2004, 14:34

Finally replaced them last night...
A couple of the plugs were a bit stiff to remove and make that terrible squeaky eeeek-eeeeek sound while they were removed. Phew! Cylinder head threads OK! Fitted the new ones no probs..
Noticed a label on the rocker cover which indicates that plugs should be replaced every 37,000 miles...I wonder if this is actually to prevent them seizing in the cylinder head rather than them actually wearing out??