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How bad do my spark plugs look? M119, unknown miles on plugs
Hi all, my R129 had about ~244k miles at the time of pulling the plugs. For some context, I bought the car a few thousand miles ago with a large stack of maintenance records going back to 2003 or so. After logging all the work done into a spreadsheet, I realized there was no record of spark plugs being changed, though I'm sure the record likely got lost over the years as the car was running fine and doubt any plug would actually last 244k miles.
That being said, I got 8 new Bosch F8DC4 plugs to swap in. Upon pulling the old plugs out I did find some pretty nasty wear around the top white end. What does that indicate exactly?
The plug on cylinder #7 was actually almost finger loose and had a ton of sludge/oil around it. I was shocked the car wasn't misfiring. Could this lead to any sort of engine damage or excess wear?
You may notice cylinder #4's spark plug is not there. I unfortunately rounded out the hex socket bolt holding the ignition coil clip down and was not able to remove it to access the plug. Do you guys recommend drilling out the bolt? I'm a little worried to ruin the valve cover as I haven't had to drill out a bolt before. Any suggestions or advice are appreciated.
The plugs look all very worn out, the gap seems very large. If a Torx socket instead of a hex socket doent work, you will need something like this: https://www.amazon.de/gp/product/B074P6DSG7/?th=1
Thanks for the annotated photo! I have seen diagrams the way you showed, I guess in my head I also picture the cylinders with the front of the engine pointing north. I will take a look at some extractor tools like the one you sent as well. Thanks!
If you’re curious on approximate mileage on those plugs, measure the gap. General rule of thumb is “roughly” 0.0006-0.0001 inches of erosion per 1,000 miles on copper plugs.
Clearer and closure-up pictures of the electrode ends would be preferable, but from that photo I would agree that they just look like worn out plugs due for replacement.
Make sure to verify the gap on each of the new plugs before installing them.
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