Yes that is the breather box and if you get a replacement, get the real one from Volvo. Read about after market ones splitting at the seams.

Just order a new o ring (I get a couple of extra ones) and your 13 mm socket out. You can remove it by feel and with a good light by reaching around the throttle body and taking your time. Held on by just two bolts and a well known and irritating leak source. The o ring on my 86 did not appear to be there because it was so smashed into the groove it looked like part of the box. Suggest soaking the old box in a can of solvent and then draining it well. There will be quite a bit of gunk in there most likely. I put some seal dressing on the engine block side before installing the box.

Here is a picture of Inga's breather box and there is an o ring in one of those grooves. But dang if I could see it at first. When you remove the old o ring be sure not to scratch the seal surface, that will also cause a leak later.



The one thing you need to pay attention to is when you put the box back on. There is a PCV tube that you do not want to push down into the block. Hold the box over the two holes and lower it into place slowly and you should be just fine.

Nice to finally get rid of that little leak, and over time oil will do a number on the windings of your starter motor.

Hope this helps,

Paul