Hm. Say you loosen but don't remove the oil filler cap. Does the blowby push the cap off the valve cover?

Do your power brakes work (the vacuum pump empties into the crankcase, so a large vacuum leak will create lots of "blow by")?

-J

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1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.