Checked the spark plugs of the 225 i just bought and thought id stick the bore scope down the holes to have a look. This what you see. No.1 - This dark black dust in the centre is just some crud that fell from around the spark plug hole No.2 - Looks like No.1 so all ok No.3 - Has me worried, wet on top, cant tell what it is or why its like that. Spark plug was dry but a bit black compared to the rest. No.4 - Like 1 and 2 so OK. Piston No.3 what im asking about. Anyone seen this before? Car drives fine, idles fine, no warnings on the dash and pulls really well when in boost.
Im no mechanic, but would that be residue from oil, which would indicate oil going past the piston rings. Any smoke from the exhaust? Next thing would be a compression test I think.
Compression test is a good idea, ill do that tomorrow. No white or blue smoke out the back. I thought head gasket but again there's no smoke. I did drive the car really steady for 10 mins before cos a little hose popped off the throttle body which caused the idle to high and run bad. I plugged it back in to get home and made a bracket to hold it in better.
Leak down test is more revealing than compression test, any half decent outfit will know how to perform.
Oil passing oil scraper maybe, its possible the cylinder could still have good compression if the compression rings are still working. Another possibility is truly knackered valve stem seals above just that cylinder. BTW I had a SAAB 900 T16S years ago that eventually cracked its head on me after the head gasket had failed but didn't blow the engine. It had a nick opened up in part of the gasket that was allowing water into the cylinder that eventually caused that cylinder to overheat to the extent that it melted the spark plug and cracked the cylinder head. Only noticed it when the engine felt rough and down on power so went to pull the plugs.
