drifter17aCommunity MemberDecember 8, 2021 at 8:37 pmMSelleenAdministratorDecember 8, 2021 at 8:43 pm
A common issue several Volkswagen engines had when I was working with these cars a long time ago was bad fuel injectors together with the turbo boost. Fuel does also cool down the pistons and chambers and if it’s running lean on one cylinder it will cause very high heat inside the chamber.
This can cause the temp in the cylinder to reach a very high temperature and it can cause the air-fuel mixture to self-ignite and you will get detonations.
I’m not 100% sure your exact engine type is affected by this, but I would definitely make a flow-test on the injectors before installing new pistons. I’m pretty sure there is a service bulletin for this somewhere also.old garage mechanicCommunity MemberDecember 10, 2021 at 11:19 pm
I don’t know about the first picture as the piston is up but the second picture you can see what appears to be minor cracks where it looks like a golden color and another one towards the lower right. On the bottom picture you can see some sort of build up towards where the piston rings would top out. If you have not put it back together add a little water to the water jacket. Don’t let the water in the cylinder. If there is a water leak it does not take much for it to drip down into the piston area.
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