Originally Posted by
FirstVolvo
The short hose from the manifold attaches to the elbow of the long hose above the oil trap, the elbow connects the long hose to the oil trap. The short, small diameter hose does provide PCV vacuum during idle and because it is also connected to the long hose, which goes to the air intake tube in front of the turbo, the long hose will limit the amount of vacuum in the hose and crankcase because air can be drawn in from the air intake tube. The air pressure in the air intake tube at idle near the long hose opening in front of the turbo is probably at a very slight vacuum and what will balance out too much vacuum in the crankcase. If the hose is clogged then air couldn't be drawn in to limit the crankcase vacuum. At higher speeds and under boost (in the manifold) the vacuum must come from the long hose near the turbo. If the long hose is clogged you won't have enough vacuum at higher speeds and higher loads.
Thanks again. I woke up this morning with the thought that the long hose to the air tube would do just as you say, limit the amount of vacuum supplied by the manifold at idle. So your post must have reached me telepathically in my sleep.
I just attempted to apply a vacuum to the end of the long hose where it attaches to the PTC. If it were clogged that should be easy to do with my MityVac. However, I could not get any vacuum at all with the hand pump. So, to me, that says that if the line has blockage it is only partial. It would be nice if there was some sort of thin flexible, yet stiff along its length, tool that I could push up around the bend of the hose and along its length (like a plumbers snake) to clear away any partial blockage. Maybe some hollow tubing that would collect gunk, instead of just pushing it ahead. I'm going to see what I can come up with. Suggestions welcome!
In the meantime, the one thing I still don't understand about this system is the function of the PTC. It seems to me it must be there to limit the flow through the long tube, but why/when I don't get. Is there any chance that even though it isn't blocked, it may be closing too much at idle?
Last edited by Pennhaven; 03-23-2022 at 12:12 PM.
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