P80 PCV System Repair on a Volvo 5-cylinder (-1998)

[cn90]

I just want to post info on hose routing.

From past experience, people on volvospeed and this forum argue over routing of the hoses.

There is disagreement among forum members, VADIS and multiple threads. Some say the hose from the top of engine (#2 in diagram below) go to the front port of the trap, some say to the passenger side port of the trap.

Anyway, below is the photo showing the inside anatomy, where oil settles down to the bottom and vapor is sucked into the intake manifold. Personally I don't think it matters which way you hook it up, but just stick to the diagram and you will be fine.

I use a little trick with the dictionary word "UPFRONT": hose from "UP" (from oil cap area) goes to the "FRONT" of the trap.

HTH.

Volvo-PCV.gif (30.19 KiB) Viewed 6026 times

[jblackburn]

Correct routing is shown on the first page of the thread. Hook up the two hoses on the top backwards, oil spews out everywhere.

[cn90]

Interesting!

If you search google images using keyword "Volvo PCV hose" (or similar keywords), you will see all kinds of hose routing.
Maybe in inside anatomy of the PCV was re-designed.
I will do my PCV soon and will cut away the old canister and post some photos!

I am thinking there maybe a 1-way valve in these ports.
Maybe someone can blow into a brand new PCV port and see what happens next!

[erikv11]

It's just a hollow plastic box, no valves. You can find several pics of cut open 850 boxes on the net, might be good to see one more though.

[cn90]

Thanks erik,

In that case (hollow box), I don't see any problem with reversing the routing?

[erikv11]

Ah you misunderstand; more correctly, "hollow box with a couple baffles" as shown. The point being there are no valves of any kind, that's all.

I'm not keen on about basing an alternative routing decision on speculation, the box is too hard to get to if your guess is wrong. It makes far more sense in this case to go with what people have observed. I think it comes down to, if you are willing to disassemble and switch it back if it doesn't work out, then it doesn't hurt to try switching them.

[jblackburn]

I can tell you exactly why that won't work. Look at your diagram. Vacuum is pulled into the whole PCV system by the hose at the baffle at the top of the canister (to the turbo). Switch those two, the oil's coming up that thing instead of coming in from the top of the engine to be sucked down by gravity to the lowest point in the box, where it drains back out.

EDIT: That's the same reason that hose is connected to the intake snorkel on a non-turbo car - to provide vacuum, and a lot of it. However, in a turbocharged car, you've got positive pressure rather than vacuum being forced into the intake manifold, so that routing won't work. But guess what? A turbo creates that negative pressure the system needs to function.

Their diagram has the locations of the ports on the canister wrong, so that's why it might confuse some people. That #2 port is really in the back of the canister (back as in facing the back of the car), as you can see in my picture.

[cn90]

Ah you misunderstand; more correctly, "hollow box with a couple baffles" as shown. The point being there are no valves of any kind, that's all.

I'm not keen on about basing an alternative routing decision on speculation, the box is too hard to get to if your guess is wrong. It makes far more sense in this case to go with what people have observed. I think it comes down to, if you are willing to disassemble and switch it back if it doesn't work out, then it doesn't hurt to try switching them.

I agree with you I will stick to Volvo OEM setup.
I think jblackburn's photo is correct.

The problem is: from reading the internet threads, it is all over the place.

BTW, this is purely academic, I just want to have a good understanding of the box anatomy and inner working.

I will swing by the local Volvo dealer to speak to the Master tech to have his blessing LOL.

[rspi]

LOL, master tech at the dealer.

I like to put things back the way I found them. That's the safest thing. I doubt the car has been driven around for 30,000+ miles hooked up wrong.

What I don't get is how you can get the wrong part. Why in the heck are the boxes designed differently? Will they fit? Or not function correctly?

[cn90]

Hey,

Does anyone know how to make this PCV Tool?





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Also, thanks to jblackburn re hose routing question that I asked before.
This you tube video seems to indicate that hose routing is important.

...I got a kit from IPD and replaced it. Since I posted it I have taken it back apart and re-routed the big hose to the intake nipple and it is perfect now...94bigandy...