I have recently replaced my rear main engine seal in my 1996 Volvo 850 (non-turbo) with 80,000 miles on it. As a reader of many posts on rear main seal problems in this forum I am aware of the excessive crankase pressure problem with these cars.

I replaced the rear main seal,replaced the oil trap(oil vapor separator (under the maifold) and was told by my tech that he had cleaned out the vacuum line leading into the flame trap holder. Still,I was noticing blowby when I pulled the dipstick with the engine running.

Yesterday, I checked my flame trap and found the tech had removed it and noticed the vacuum line was detached from the flame trap holder. I removed the vacuum hose from the vacuum tree and probed the line. FOUR INCHES OF THE TOTAL SIX INCH LINE WHERE PACKCED SOLID WITH CARBONIZED OIL WITH THE CONSISTENCY OF CONCRETE. I could not probe and clear the line with rigid and pointed coat hanger wire and broke the line.

I immediately called my volvo parts supplier and asked for the the vacuum hose and rubber connecters. He said these were special order items because not many customers ordered these parts. He did volunteer to look for some "out back". Luckily, for me, he found some left over from a previous customer's order. I installed it and drove the car fast and hard. I checked the oil dipstick with the car running and NO MORE BLOWBY! The cost of hose and connecters $2. My time to disassemble and reinstall was 30 minutes.

Conclusion:
THE COST AND TIME TO CHECK THE VACUUM LINE AND INSTALL IS MINIMAL. ALWAYS DO THIS BEFORE THE MORE EXPENSIVE JOBS. I SUSPECT DUE TO THE NARROW WIDTH OF THE HOSE IT MAY CLOG REGULARLY. IT MAY SAVE YOU THE COST OF A REAR MAIN SEAL AND OIL TRAP (VERY EXPENSIVE AND EXPENSIVE IN TECH LABOR). I WONDER IF SERVICE SHOPS ARE CONCENTRATING ON THE HIGH COST REPAIRS AND NOT THE SIMPLE AND INEXPENSIVE VACUUM LINE REPLACEMENT. (MY PARTS GUY SAID THAT THE SERVICE DEPARTMENT GENERATES HIGH DEMAND FOR REAR MAIN SEALS AND OIL TRAPS, BUT LITTLE NO DEMAND FOR THE $2 CLAMPS AND HOSE I PURCHASED. IS THIS SIMPLE IGNORANCE OR PROFIT MOTIVE AT WORK?