I wanted to share a recent experience related to crankcase service on a 5-cylinder Volvo turbo engine. I know that the PCV system has been written about before, but I wanted to take it to the next level and share some insight that people are probably overlooking.

An important part of the system includes the oil drain back to the oil pan. I recently pulled one apart that was completely plugged. You can test for this by blowing compressed air in the oil drain at the block. If the oil doesn't bubble or you can't otherwise get pressure to escape, the entire oil channel is plugged. This problem will require the removal of the oil pan to clean out, otherwise, the PCV system is non-functional and you will waste your money.

The first picture shows what the drain channel looks like in the block with the oil pan removed. You have to dig out the sludge and run some compressed air and brake clean down the channel until you are satisfied that it is clear. I ended up doing the final test by putting the shop vac up against the port on the side of the block and was able to get air free flowing so I declared the channel clean.

The second picture is the pan itself. I first sent this thing out to the machine shop to be high temperature washed and it came back very clean. However, the square drain channel was not clear so I had to do some digging to get it open. The channel runs down the pan and makes a u-turn in a j-shaped channel. You can barely see the other end where the oil drains because of the baffles. After digging out the sludge, I poured lacquer thinner in the channel and worked a piece of mechanic's wire in and out of the channel and then the other end of the j-shaped channel which is round. At the moment that you clear the channel, the lacquer thinner will drop down and pour out the other end since it is higher than the channel that returns the oil to the pan.

I did a final cleaning of the clean pan after it came back from the machine shop using Purple Power to wash the inside/outside of the pan, and then a garden hose to make sure that everything was clear and clean.

As far as I can tell, Volvo designed this oil drain with a type of trap like a sink to keep anything from going back up the channel. I can see this channel getting plugged up on higher mileage models and this needs tested (like described above) before replacing the breather box/oil separator.

 

Many thanks. I've never SEEN the oil return passage.
How hard was the clog? By that I mean easy to dig out or was it diamonds?

I was wondering about merely draining the oil and adding 7 quarts of lacquer thinner to the pan and letting it sit.

 

I used a medium screwdriver to dig down and remove most of the tar. Once you get the majority out, then you need to fill the tube with lacquer thinner and snake the passage both ends with mechanic's wire. When I finally broke through, the level dropped. Until I broke through, I believe that the thinner would have evaporated.

Bad idea filling the oil pan with lacquer thinner. It is basically like clearing a clogged drain. Once cleared, I washed it with high pressure water and soap. Its clear now.

 

 

Changing the plastic box is the easy part. Just toss in the garbage. The oil pan is another story.