Ben Jordan Posted February 18, 2006 Share Posted February 18, 2006 I have just been changing the spark plugs on my 3.9 V8 and as i was changing the last plug (front offside). The plug sheered in half leaving just the thread in the head I have the plug above the thread with a straight conductor wire coming out but there seems to be some bits missing, so they have probably fell onto the piston. So the head has got to come off to a ) get the thread out and b ) remove the pieces of plug. How big a job is this? And what should i know before starting? Thanks. Quote Link to comment Share on other sites More sharing options...
white90 Posted February 18, 2006 Share Posted February 18, 2006 breaking plugs is not that uncommon try tightening the threaded section left in there a tad then try undoing it again, may be worth a wd40 spray before hand. you need to get that piece out first before thinking what has fallen inside my guess is nothing has. once the threaded piece is out you could turn the engine over by hand till the piston is TDC then try looking inside with a decent torch, try the hoover to suck any debris out at leat at TDC the valves will be closed and you could try compressed air to see it you could extract any wayward bits and pieces. Quote Link to comment Share on other sites More sharing options...
geoffbeaumont Posted February 18, 2006 Share Posted February 18, 2006 I have just been changing the spark plugs on my 3.9 V8 and as i was changing the last plug (front offside). The plug sheered in half leaving just the thread in the head I have the plug above the thread with a straight conductor wire coming out but there seems to be some bits missing, so they have probably fell onto the piston.So the head has got to come off to a ) get the thread out and b ) remove the pieces of plug. How big a job is this? And what should i know before starting? Thanks. Not sure why removing the head would help with getting the thread out? Presumably, if you have enough of the plug to suspect there are bits dropped off inside, there's a hole through the bit that's in the head - can you hammer somthing into that (say a large crosshead screwdriver or even better an torx or alan key bit) and use it to unscrew the plug? You might well find the missing bits are still attached when you get it out, which would save you a lot of hassle! Taking the head off isn't difficult, but you'll need to lay in new gaskets (head gasket, valley gasket, rocker cover gasket) and new head bolts (don't even think about reusing the old ones - a world of pain awaits you there - trust me on this one... ). Get the compound type head gaskets, not the older tin ones - a bit more expensive but much better. Might as well do the other head gasket too while you're in there. Expect it to take you a couple of days, as there's all the inlet and fuel injection kit to dismantle to get to it It is possible to just slacken off the inlet manifold and remove one head without dismantling everything else, but you're unlikely to get a decent seal on the valley gasket afterwards, so this is a bad idea. Only consider it if you absolutely have to get the job done and the car back on the road as quickly as possible, and reckon on spending next weekend stripping the rest of it down to fit a new valley gasket (and the other head gasket, while your at it). So try getting the rest of the plug out first... Quote Link to comment Share on other sites More sharing options...
Ben Jordan Posted February 18, 2006 Author Share Posted February 18, 2006 The thread has snapped off flush with the top surface of the head. So there is nothing to grip. To be honest it felt like the plug had welded itself in. It did take quite a bit of pressure before breaking. Wish i left it in there now. Quote Link to comment Share on other sites More sharing options...
white90 Posted February 18, 2006 Share Posted February 18, 2006 well that scuppers my ideas. head off time,machine shop to remove if you can't then follows geoffs instructions. Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted February 18, 2006 Share Posted February 18, 2006 Is there any way you could screw a reverse-threaded extrator thingy intothe remains of the plug? Quote Link to comment Share on other sites More sharing options...
white90 Posted February 18, 2006 Share Posted February 18, 2006 or save the ££ and fit a TDI now. Quote Link to comment Share on other sites More sharing options...
Ben Jordan Posted February 18, 2006 Author Share Posted February 18, 2006 Having push rods i wont need to worry about the timing will i? I will try a thread extractor in the morning if i have one big enough. Quote Link to comment Share on other sites More sharing options...
white90 Posted February 18, 2006 Share Posted February 18, 2006 grim but it my be better to remove the head and deal with it to save metal swarf dropping into the bore Quote Link to comment Share on other sites More sharing options...
minivin Posted February 18, 2006 Share Posted February 18, 2006 Having push rods i wont need to worry about the timing will i? I will try a thread extractor in the morning if i have one big enough. don't, head off and get it on a bench, if a hardened Eezi-out cracks on you your duffed big time! If you want to do the work yourself and got a pillar drill, I'd tip the table so it's at the same angle as the head, clamp the head and find a drill bit slightly larger than the internal dimensions on the spark plug slug and drill it to give you a datum. Check the dimensions of a good spark plug to find out what the thread form is, look in a chart and find the core diameter of that thread form is, find a drill of that dimension and take a second cut. Hopefully now the threads should be just breaking through so you should be able to use a 1st tap to gently teese the last bits out, but don't try to cut the thread as you may take the lot out by cutting it half a TPI-out from what it is at present. If you screw up the threads, Wurth do a nice kit for doing a solid thread repair that is much better than Helicoils Quote Link to comment Share on other sites More sharing options...
BogMonster Posted February 18, 2006 Share Posted February 18, 2006 I nearly had the same thing. The plugs in the Thor V8s are fancy platinum tipped ones that are supposed to be good for 72k miles or something stupid, mine got changed a couple of years ago as I think the quoted service life figure is just stupid (though when you see the cost of the Thor plugs you start to realise why ... about £8 each IIRC!) I took them out for a look just to see if they looked OK a few months ago, I had awesome trouble with about four of them, they were really seized in the head and came out so far with that "skreeeeeeeek" that bolts usually make just before they snap off... I was having kittens at this point and nearly left them but I decided they would only get worse so slackened each of the troublesome ones off about a turn and hosed a load of WD40 in around them, left for a while, hosed a bit more in and wound them back in a bit, after that they came out OK. They went back in with a fair bit of copper grease on..... I guess the problem is that the plugs are (presumably) some sort of steel and the head is aluminium. And as Land Rover owners we all know what happens when you put those two together.... From now on I am going to take them out at least once a year for a look just to make sure they haven't seized in. Quote Link to comment Share on other sites More sharing options...
Ben Jordan Posted February 18, 2006 Author Share Posted February 18, 2006 What is the plan for getting the head off? Quote Link to comment Share on other sites More sharing options...
Ben Jordan Posted February 19, 2006 Author Share Posted February 19, 2006 Im going to start the job this morning, what should i be looking out for as i strip the engine? i.e. wear and parts that need replacing. The engine has covered 140,000 miles and by the looks of things it has not been serviced very well. Do cylinder heads normally outlast the engine or do they need rebuilding from time to time? What parts i.e. gaskets and studs will i need to put it all back together? Which are the best ones? And the best place to get them? Quote Link to comment Share on other sites More sharing options...
minivin Posted February 19, 2006 Share Posted February 19, 2006 Suppose the first thing is to get some rag and put it down the valley area above the cam, dropping a bolt into the bottom regions will tend to ruin yer day, don't ask how I know Quote Link to comment Share on other sites More sharing options...
Ben Jordan Posted February 19, 2006 Author Share Posted February 19, 2006 Suppose the first thing is to get some rag and put it down the valley area above the cam, dropping a bolt into the bottom regions will tend to ruin yer day, don't ask how I know Thats a good idea. Quote Link to comment Share on other sites More sharing options...
rtbarton Posted February 19, 2006 Share Posted February 19, 2006 Could you try warming the head and using an Easy-Out first of all? The aluminium will expand more than the steel so it may just slacken its grip on the plug. I know its a bit of a longshot, but any port in a storm! Quote Link to comment Share on other sites More sharing options...
geoffbeaumont Posted February 19, 2006 Share Posted February 19, 2006 I know we said it before, but if you're in to heads off territory and thinking about what else needs doing, timing gear - preferably can, tappets, maybe pushrods and rocker assemblies too, but definitely the timing gear. Trust me when I say it's not wise to ignore this advice... Quote Link to comment Share on other sites More sharing options...
geoffbeaumont Posted February 19, 2006 Share Posted February 19, 2006 Trust me when I say it's not wise to ignore this advice... ...and here's why Quote Link to comment Share on other sites More sharing options...
VERY OLD DISCO Posted February 19, 2006 Share Posted February 19, 2006 Its to late now but sometimes if you get a bit of tube just big enough to fit over the insulator, (but not so small as to bind on it) it should rest on the hexagon flats but be too small to fit over if you know what I mean, then strike it with a hammer a couple of times. This compresses the alloy seat a small amount and breaks the seal of the thread. dont break the ceramic if you can avoid it (in your case ignore this). This also work well on seized wheel nuts etc. Blue tack on the end of a piece of dowel will lift any ceramic bits, one of those magnets on a stick will lift the steel bits. any bits left in will jam between the piston and cylinder, best lift the head. Geoff Quote Link to comment Share on other sites More sharing options...
Ben Jordan Posted February 19, 2006 Author Share Posted February 19, 2006 I know we said it before, but if you're in to heads off territory and thinking about what else needs doing, timing gear - preferably can, tappets, maybe pushrods and rocker assemblies too, but definitely the timing gear. Trust me when I say it's not wise to ignore this advice... This is what i am thinking and if i do all that i might as well do the bottom end and have the engine rebuilt. All over a spark plug it's never ending Quote Link to comment Share on other sites More sharing options...
geoffbeaumont Posted February 19, 2006 Share Posted February 19, 2006 All over a spark plug it's never ending It's a Range Rover... Quote Link to comment Share on other sites More sharing options...
Ben Jordan Posted February 19, 2006 Author Share Posted February 19, 2006 It's a Range Rover... The Defender's dont seem to be much better I think the quote should be "It's a Land rover" Quote Link to comment Share on other sites More sharing options...
Ben Jordan Posted February 20, 2006 Author Share Posted February 20, 2006 Im even considering breaking it Quote Link to comment Share on other sites More sharing options...
02GF74 Posted February 20, 2006 Share Posted February 20, 2006 Im even considering breaking it every mechanics nightmare at least it sounds like you have good access to it. looking at similar plugs that cam out, do they have the crushable washer or taper? (think v8 has former). but as you have lost the hex head what I was going to suggest isn;t going to help. If you havent taken the head off; then use a punch or narrow chisel to smash the cnetral insiulator, Then with a hacksaw blade, start to saw from the inside outward to weaken the plug that is left. If you make 2 or more vertiacl cuts, you may be able to hammer hte the piece in wards so they grip less. It ouwld have beem easier iwth the hex bit on! I suspect you are not going to be able to do that so heads off. If you mess up the head; check prices of recon and ebay, I have a pair of SD1 heads, need skimming and guides that you could use to recon or as surcharge exchange if you damge your head. (dead cheap). 140,00 miles = probably needs cam + followers; if no knocks from bottom end, then you could leave that but best to overhaul it. Once you start taking bits off and replacing, the scope of the recon increases, as does the cost (no need to aks how I found that out!) The only good thing is that pasrts are realtivrly cheap - see paddocks/craddocks/ebay. Quote Link to comment Share on other sites More sharing options...
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