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It seems to me that the narrow plastic vacuum line which is suseptible to oil seepage and heat to bake and clog the line is an engineering defect. The repair maunuals state that "compressed air should be used to clear the flame trap hoses when cleaning or changing the flame trap" (Haynes). Perhaps it should be highlighted in the manual to get peoples attention.
My tech has 30 years of working on Volvos and he removed the flame trap rather than checking the small vacuum line for blockage. I here that the 70 series Volvos have the flame trap removed. Nevertheless, my parts guy says that if a Volvo originally came with a flame trap installed (as 850s did), they still re-install them during maintenance. I had to insist that my tech follow up with vacuum hose and oil vapor separator replacement after he replaced the rear main engine seal. His explanation (for resisting my request) was that new rear main seals are improved (more felt) and that should solve the problem. He is a dealer trained and employed tech who works for me after hours. I believe,as you do,that a rear main seal leak is a symptom not the cause of the problem.
My solution is to thoroughly check the flame trap,housing and connecting lines every time I change the oil and filter (3000 mile or 3 months). I also occasionally remove the oil dipstick after a hard drive with the engine running. If I see any blowing activity (blowby) from the diptick neck, I suspect a renewed clogging problem. Eternal vigilance seems to be the only answer on this issue.
Dan
Dan
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