I have never heard of a PCV valve on any volvo. Other makes of car have a PCV valve and its function is pretty much the same, so I guess he may be talking about the flame trap. The other possibiility is that he is talking about the breather box/oil separator. This item IS under the manifold. Don't know about 850s, but on the 200/700/900 series it can be a bear to get out without removing the manifold (though it can be done). Maybe on the 850 you can't get it out without removing the manifold first?. I have seen other posts that say there have been problems with the breather boxes plugging up on the 850s. If you can locate the breather box, there are a couple of ways to check if it is really plugged.
- remove hose to breather. remove dip stick. Attach a hose to the end of the dipstick tube and blow hard down it! If you can hear air coning up out of the top of the breather box (where you removed ths hose) it is probably not toobadly plugged.
- attach short hose to breather box, run it straight up (or as straight as you can) and insert a funnel in the open end and pour motor oil into it. It should drain straight through. If not, the breather box may be plugged. Make sure you don't overfill with oil if you do this though (you can always drain some out via the oil drain plug if you do).
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'95 940 Wagon, '85 240 Wagon (RIP), '91 740T Sedan