Removing PCT Valve and Cleaning [1997 Volvo GLT Turbo]

[jblackburn]

I can't tell you how the thing works, but I'm going to add a bit of out-loud thinking.

What I do know is there's an electrical connection for a heater only. The intake manifold is applying a constant pressure to the vacuum nipple, so there is no way that there is any flap or anything in there that closes, as that vacuum can't be regulated, except by the engine speed. More RPMs = faster suction = more vacuum pressure.

When the vacuum hose on mine kept falling off, I would still have PCV pressure. As soon as I reconnect it, voila! pressure gone.

I think it's a good idea to drill out the hose. The smallest size drill bit in my kit (don't know the number off the top of my head) fits through the small hole in the vacuum side; I'd go 2 sizes up from that and see what result that gets you.

The other idea I have is to put a branch off of that port and run it to one of the unused lines on the vacuum tree if you're in need of more suction.

Ideally, the PCV system was designed to handle the blow-by and pressures from a NEW engine. I'm not sure that it was designed to take into account the pressures that would come up down the road when the engine hits 200,000 miles and the seals, rings, etc. begin to wear out. That is why some people still have positive pressure even after replacing the entire PCV system.

[jblackburn]

Absolutely.

I talked to one of the Volvo mechanics about getting the system done 3 years ago when I got the car, and he didn't even mention cleaning the PTC until I asked about it. He said "nah, it looks fine." They're obviously not "just fine", or everyone wouldn't say it needs to be cleaned

Call back and ask whether they did or not. If they didn't clean the ports out, that's probably exactly why you've still got smoke after having it done.

[1997volvo850]

My thinking on cleaning the PCT valve is evolving as I understand this system more.

I originally took the PCT valve out of the air intake hose to clean it. It cleaned up fine and I was able to
replace it just fine.

Others suggest removing the air intake hose and then either remove the PCT to clean or clean
it in place. I could not get my air intake hose off using reasonable force so I didn't do this.

I'm thinking that a reasonably quick solution, given the heavenly properties of Seafoam, is
to simply remove the large vacuum hose from the top of the PCT valve and spray Seafoam in there.
Then examine for clear opening. I could see applying shop vac to clean her out quickly.
This would be more of the regular easy PCT maintenance, maybe every 20K? This might
extend the life of the PCV system as a whole.

What do you think?

I'll likely be working on the PCV system this weekend and will post more as I discover it.

Justin - I believe the increased vacuum as the engine power increases is what is meant as
the varying vacuum that regulates the PCT valve. All I was referring to is the PCT valve acting
differently based on level of vacuum. You've clearly explained how the vacuum level changes.

I was NOT thinking to increase the vacuum to the small vacuum hose on the side of the PCT valve.

What I am thinking is to enlarge the hole that goes into the air intake pipe thus allowing the increased volume
of blow by gas vapor from my old engine to escape more effectively. That is, drill a slightly larger hole in the bottom.
I think it's about 1/4" now. I need to calculate the area first but I'm thinking to increase to maybe 7/16".

I would love it if you try this on your car first just in case my calculations are off.

If you try this, measure gas pressure from dipstick. How long does balloon take to inflate. Then
drill. Measure pressure again. This is what I am thinking to try. Increase hole size until pressure is gone.

[jblackburn]

I'm thinking that a reasonably quick solution, given the heavenly properties of Seafoam, is
to simply remove the large vacuum hose from the top of the PCT valve and spray Seafoam in there.
Then examine for clear opening. I could see applying shop vac to clean her out quickly.
This would be more of the regular easy PCT maintenance, maybe every 20K? This might
extend the life of the PCV system as a whole.

Yeah, that was a suggestion I made in the write-up procedure thing I did. Pouring it down the hose from the top of the engine into the oil separator box would also probably be a good idea every 20-30,000 miles or so too, just to keep it cleaned out.

The entire intake hose comes out if you can get to the clamp at the back of it - a long flathead screwdriver or 7 mm wrench with extensions works great, and it's much easier than trying to get the PTC back in while in the car. It LOOKS like a pain, but it's really not too terribly hard.

That said, I refuse to touch either of the 2 hoses back there unless they fall off again. When I put in the big curvey hose from the box to the PTC, it's like a few millimeters too short, and the stupid elbow ends to the hose that connect to the PTC fell off about 10 times and dropped into the depths of the engine before I could get them to stay on. Most. annoying. thing. ever.

With the small vacuum hose connected, though (it kept blowing off the intake every time I'd put my foot down - I recommend putting a clamp there), I have no pressure problems anymore. I think as my car continues to get older, it may develop again - I get an occasional puff out the tube if the AC is running while idling. But I'm not concerned about it for now - the system is MUCH better than it was.

I think your idea of making the holes bigger would certainly help it. I don't know why the vacuum hose part is so teensy at the bottom of the valve, and it seems to me like it should be bigger in the first place to keep from clogging. That one's a very very small bit size.

The question is, in doing this, will you throw a vacuum code? I don't know the answer to that question either

[jblackburn]

Hmm, your compression numbers are a little low, but that's something I'd expect for an engine that's had 200,000 miles on it and hasn't been taken care of meticuously its entire life.

There's no reason to get rid of it at all, just keep driving it. It still runs fine, the rings are a little bit worn, but that's no reason to get rid of it.

Sure, give the seafoam another try. The good thing is that the crankcase is ventilating much better than it was an you're less likely to blow out a seal now.

My mom's still got the same 1974 BMW she was given when she was 16. The engine or transmission have never been overhauled, and it burns oil like crazy after it sits for a while, but it still runs great.