Spark Plug Problem

[slbfish]

I have a spark plug problem with my 2005 c180k coupe. The mileage is 89000 and i want to change the spark plugs as they have not been done since 49000 but one seems solid. It moves a quarter of a turn and then goes solid. any suggestions???? Thanks

 

[ray_hennig]

I had that once ...

I have a spark plug problem with my 2005 c180k coupe. The mileage is 89000 and i want to change the spark plugs as they have not been done since 49000 but one seems solid. It moves a quarter of a turn and then goes solid. any suggestions???? Thanks

Same thing for me once on an M110 6 cyl engine. It was the rear-most plug.

This is NOT a recommendation - wait for the brainy boys. This is what I did:

Brute force! It was difficult to reach and my plug socket seemed to get locked between the rocker cover and the rear bulkhead. All in all it was a very tense time.

Eventually, having broken the insulator I got the plug to loosen. When I thought it was about to release, I vacuum cleaned out any debris that might have been created - I did not want bits of insulator ceramic dropping into the cylinder.

Finally, I got the old plug out and installed the new. I applied grease to the threads and then started screwing it in until it locked - then removed it again. I continued like this, even re-applying grease from time to time. Each time I went a little further and then removed it again. Finally, it reached 'home' and I could feel the washer compress. I tightened it down once and for all and all was well.

Things were fine after that and there were several plug changes before I let the car go.

All the time during the tightening process I made sure the socket was vertical and I never applied excessive force.

The interesting thing was that the old plug had what looked like molten, light-coloured metal over the end of the threads. This must have stopped the plug's easy removal.

Do wait for more informed opinion than mine and bon courage!

RayH