After driving home from having my thermostat housing replaced,my check engine light came on.Thinking maybe a vacuum line was loose,I returned to have my mechanic check it out.After checking hoses,fittings,etc,he opened the oil filler cap(it was hard to remove)and immediately said it was a diaphragm in the valve cover area that he estimated would cost $500.00 to repair.This sounds bizarre to me,or is it just another strange mini problem?

Thanking all input in advance.....

2007 R56 S

 

If the internal positive crankcase ventilation (PCV) valve is seized shut, you could have a internal vacuum issue.
See the lower part of page one and read up on the valving that's apart of the valve cover:
* https://www.northamericanmotoring.co...-and-more.html

- Erik