97 Turbo PCV routing - which is correct?

chuckcintron · Post by **chuckcintron** » 15 Jun 2008, 18:43

OK, I've been reading all the posts regarding the PCV routing at the cannister for pre 1999 turbo models.

Here's the issue I'm having. I did the PCV job about a year ago, and have since developed more oil leaks and now clearly positive pressure blowing out of the dipstick.

We have a dilemma which I think I'm going to have to figure out by removing my cannister and cutting it in half on the bandsaw.

Who is correct? Is it FCP Groton (Volvo's VADIS) diagram:

http://www.fcpgroton.com/product-exec/p ... gory_id/65

Or is it the correction sticky, which references this procedure (and routing):

http://lakesidedp.com/uploadpics/pcv/pic12.jpg

As you can see they are in stark opposition. It's really odd that I have it according to the second version and I've now got a complete failure of the repair. Everything else was clean & clear (PTC, engine block ports, etc.) I also replaced all the hoses.

I'm going to order a new cannister and hopefully next weekend do this job again. Before I do it I'm going to bandsaw the old (well, a year old) cannister and see what is what.

-Chuck

Post by **Ozark Lee** » 15 Jun 2008, 19:47

On a '97 I can't tell you for sure. On my '96 turbo the pipes from the oil trap were backwards from what FCP shows. The line nearest to the block went to the top of the cam tower and the one closest to the front of the car went over to the intake hose.

...Lee

Post by **MadeInJapan** » 16 Jun 2008, 16:27

After you band saw it, please post back. I have gotten a lot of PM's saying on certain models my sticky doesn't hold water and so I may need to revise it but without further info, it's hard to know what to do.

chuckcintron · Post by **chuckcintron** » 16 Jun 2008, 19:55

Will do, this Saturday (*if* my wife allows me back in the garage...over 200 hours in there over the last month).

Yeah, re: my other post, yes the PTC is perfectly clean so something else is going on to cause the PCV to be clogged again. Man I hope my RMS is not toast.

-Chuck

chuckcintron · Post by **chuckcintron** » 20 Jun 2008, 21:13

Here's the PCV cannister, cut open. Sorry for all the plastic dust in the photo, didn't have time to clean it. I believe Dave's assessment was correct, but I think the theory of operation may be a bit different than first assumed.

The vacuum line that goes to the PTC assembly (on the intake accordion pipe) is supposed to go to the center hole -- the hole which is further away from the engine block when the cannister is installed. That's the instruction according to the updated PCV repair guide, sticky at the top of this forum.

However, according to Volvo that big vacuum line should go on the other port -- the one closer to the engine block.

See that integrated circular "wall"? I believe that is designed to equalize the vacuum across all the other ports in this cannister. If that wall wasn't there, for example, the suction from that top port would "short circuit" to the other port right next to it -- starving off the other ports from vacuum.

The only reason I can think of for Volvo to switch their recommendation to move the vacuum line to the non-walled top port is because they want the bottom-most vent port to see more vacuum than the original configuration would have provided. Maybe because that bottom port is prone to clog?

I have the intake manifold off right now and am waiting to put it back together until I can decide which way to pipe it. The "corrected" version, or the Volvo version???

What do you guys think? Dave?

BTW, I have NO idea why my car was blowing so much smoke out of the dipstick. This cannister was as clean as if it were new. The ports on the engine block were not clogged. My PTC was not clogged. Even so, I recleaned and reamed out everything. I even blew 100PSI compressed air into all the circuits (the top engine block port is routed to the oilpan -- I felt air blowing out of the dipstick tube).

So, if I have an unobstructed path from the dipstick to the cannister, and I'm pulling a good vacuum through the PTC I ought to not have any positive pressure coming out of the dipstick. I REALLY hope this is the case when I reassemble this Saturday morning...

Post by **tailor** » 20 Jun 2008, 21:25

What do you guys think? Dave?

Well it's not Dave, for what it is worth, prior to changing the PCV myself it was done by Volvo . It was routed as the pinned section above and I did it the same way, perhaps by fluke.
So far no problems!

Post by **MadeInJapan** » 20 Jun 2008, 21:51

Very interesting...much different design inside than I had originally been told (and have diagrams) and what I assumed. However, still I think that what is described in the pinned section is best. Yes, the round section should cause more vacuum into the side of the engine (if I'm reading your write-up correctly) and hopefully keep clogging to a minimum.

In regards to your positive pressure, it's hard to say. Obviously it's not the PCV system related. Have you done a pressure test on each of your cylinders?

chuckcintron · Post by **chuckcintron** » 21 Jun 2008, 06:19

I haven't checked the cylinder pressure. Zero smoke out of the exhaust, however. Good idea to check, though...

I'll put it back together this morning, the pinned way, and see what it looks like. Maybe it just wanted some attention.

With the design of this cannister, I don't really think there's all that much difference between the two routing choices. If either one was 'wrong', I can't really see that it would cause a failure of the PCV system. There should be a TON of vacuum being pulled through that thing, via the large vacuum line back to the PTC.

-Chuck

Post by **MadeInJapan** » 21 Jun 2008, 06:26

I agree with your assessment. Please post back as to whether your pressure equalizes or not. For the life of me I really can't think where else to look except the cylinder walls/piston rings themselves....or (new thought) clogged exhaust- but then you would have terrible idle and strange driving behavior out of the car.

chuckcintron · Post by **chuckcintron** » 21 Jun 2008, 16:55

Well, after buttoning everything back up I'm back to normal -- just slightly negative pressure at the dipstick. There must have been some internal blockage behind those ports on the block. Last time I did this job I "lightly" cleaned them out. This time I reamed them out with a coathanger wire, 12AWG solid copper wire, a long nylon wire tie and finally with 100PSI compressed air.

Looks like my P0172 may have cleared now, as well. Will know for sure after driving again tomorrow.

One other thing I did this time -- I never liked that bottom short hose that connected from the back of the cannister to the block. It came with an aluminum sleeve around it, which made it impossible to really tighten down with the hose clamps. So, I slit that sleeve with a hacksaw. Much tighter seal now.

I will do a leakdown test on the engine some time (out of curiosity), but for now I think the problem was with the PCV. Let's hope it lasts longer than a year this time!

-Chuck