Valve guides worn – symptoms and fix?
2012 Astra 1.7 CDTI has blue smoke on overrun and high oil consumption lately. Compression good, no blow-by. Suspect valve stem seals or guides worn. How to tell difference, and is it worth doing guides only or full head refresh?
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Blue smoke on decel/overrun with good compression usually points to worn valve guides or bad stem seals letting oil down the stems. Guides wear causes excessive stem play, seals fail from heat/age. Pull the cam cover, check rocker/valve movement- if wobbly, guides are shot. I did guides + seals on mine- better than seals alone if play is bad. Ordered bronze valve guides and Viton seals from https://elartcom.eu/categories/cylinder-head-parts-123 - they have sets for Opel diesel engines, including oversized if needed after reaming. Also grabbed new valves while at it. Machine shop honed guides to spec, installed everything- smoke gone, oil use back to normal after 12k km. Quieter top end too. If you're refreshing, their page has matching parts grouped nicely- saves hunting around.