Stuck spark plug
 

After a service at A4 Audi (Glagow's independent Audi specialist) it was reported that my number 5 plug is stuck. They had the car in last week to see if a long soak in WD40 might free it, but to no avail. :(

Next step, they say, is to take the head off and send it to an engineering shop to get it removed. This is going to take days and cost in the region of £300 just to remove and refit the head, plus the engineer shop costs. :-(

Is this a common problem and is there another approach that anyone has had any luck with?

That's a good price.

Have they tried removing the plug whilst the engine is hot?

I don't know if they've tried it with the engine hot - is that a likely fix? If so, I'll have a go myself. They seem to be terrified of breaking the plug

Spark plugs
 

The spark plugs can become very seized if they have been there a long time. If the engine isnt misfiring on cylinder 5 I would be tempted to leave it for now.

But if you wanted to try and replace it I would try and get the engine nice and warm and then try to release the spark plug with a long breaker bar....but you want to be careful not to break the spark plug, however u may be unlucky and someone may have cross threaded the spark plug.

The only other option is to remove the head and have it drilled out. But if you are going to have the head removed then you might want to think about renewing the intake manifold gaskets and changing the cambelt at the same time, I wouldnt worry about water pump and thermostat at this moment in time.

Mind you it might be worth thinking when the cambelt change is due cos you would probably be better off removing the head then.

If you do decide to take the head off and sending to a machine shop proves expensive, then I have one in my garage from an AVP engine which is spare.

I know half-remembered knowledge is more dangerous than ignorance, but the volumetric coefficient of expansion of aluminium is approx. twice that of steel so the head would grip the plug tighter when its hot. i.e. it wont "expand" the hole, it will make it smaller and, as the plug expands, it too will fit tighter in the 'ole. So, according to my theory, you should stuck it in the freezer..... :D

I am very happy to be proved wrong here +++

you are probably right
 

in which case head off or driving to the arctic are the only options possibly...lol

mgiht not be the same thing but I was once told that the platinum spark plugs get seized in the ford ka engine...could the same thing have happened here??

I replaced mine not so long ago and a few of them were really tight. In the bottom of the spark plug recess was black tar like stuff, i'm not sure if this made things worse or even how long the plugs had been in there. 8's a 96 and the plugs had Audi rings on them so who knows.

If you're going for it use a T bar to get evenish pressure if you can.

Also all that WD and sh it in the hole will now go into the hole when you do get the plug out, if petrol and gas don't come out under pressure WD isn't going in just being sprayed in there.

No the hole expands as well. For example on suspension arms when you try to press out bushes aluminium arms need less heating to get them out then steel/cast iron arms as aluminium expands less.

You can also try to freeze the plug itself using something like plumbers pipe freeze.

Or just attack with brute force and if it brakes or damages thread just drill it out and put a sleeve in. I think damaged thread repair with sleeve costs around £60. They just turn engine to position where valves are closed for that cylinder, drill out a hole, rethread it with bigger thread, blow out shavings with compressed air and put in sleeve with new plug.

If the old plug is not giving any running problems might as well leave it there.

I agree with ainarssems. Don't worry about it until its an issue. When it is an issue, go down the brute force root. Make sure you use a 6 sided plug spanner for maximum grip and a long breaker bar to exert torque slowly. If it snaps, get that cylinder to top dead centre on the compression Stroke (valves both closed) And get a piece of wood dowel the same size as the plug housing and drill a 4mm hole to start with in it with a pillar drill. You now have you drill guide. Measure the amount of plug left in the hole, mark you drill bit so you don't drill to far ( preferably not as far as the electrode) and steadily increase the size of the bit until about 10mm, then try a stud extractor. If that fails, continue drilling until you drill out the plug and the heli coil blow out any swarfe, vacume out the swarf, then blow out the swarfe and reasemble.

As Ainarssems and Conan say....

All I'd add and I know it sounds silly but try tightening it a tad first then slacken. Back and forward a bit until if feels like it'll come out.

Although if it ain't broke why fix it ;)

Stew,