good call on removing the heads if you had all those issues.

timing chain guide rails replacement requires removal of the heads anyway and make sure to use proper sealant on the timing case and head gasket edges, It was originally bonded with loctite 5900.

If you had only the air pump problem - then many mechanics have repaired that fault with a liquid product made by BG I think and some people online have also used combustion chamber cleaner also.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)