Removing PCT Valve and Cleaning [1997 Volvo GLT Turbo]

[whoa]

McGuyvering it should be fine. Just do something clever to keep the PCT from leaking or pulling out. Maybe some real long zip ties or chains of zip ties around the hose? A little silicone would be fine, I think. It's vacuum there, in the intake tube, not pressure, and I doubt the temperature ever gets all that high.

The stiff hoses get brittle and gunked up, so you really want to replace those. While you're in there, the other stuff is a "might as well" thing as far as I can tell. My separator box seemed fine, as did the engine passages. The other thing is that I think crankcase pressure increases as rings, valve seats, valve guides and stem seals wear, so the PCV system becomes more critical over time, and probably liable to clog up more quickly.

I'm going to check the PTC nipple a lot more frequently than every 60K. You can just pull off the little vacuum hose and see if a drill bit hits gunk.

[1997volvo850]

For the white smoke in my exhaust: I am not losing coolant (unless the head just went on it). The smoke
appears to be less now but it does not go away after it is idling for ten minutes or so.

In your tutorial please address dealing with the fuel lines. Some tutorials talk about moving them out of
the way and others talk about doing the PCV system without moving them.

On my 850 these fuel line hoses are rigid. I'm very nervous about moving and bending these lines. What
are the chances these 13 year old lines will crack or break. Also some close ups of bleeding the gas pressure
would be great.

Also make sure to cover how to keep from destroying the injectors. Set these on a blanket? Guess it
depends on if you remove them or just move them up.

Oh yes, please use my pictures if you need to. If my MacGyver tricks don't work and I end up buying
a new air intake hose I will take detailed pictures of the install/removal of the PCT valve. Not planning to
buy it at the moment.

I like the picture of you attacking your intake manifold. Should be the cover photo for the tutorial.

Take pictures of the condition of everything you take off your car. It will be useful to say this is the condition
of the PCV system after XX K miles. I am also planning to tear apart the oil separator and see what's in there
and the true condition of the oil separator. If you do the same some pictures would be so cool! I'm very curious
whether the entire system really needs to be replaced as opposed to cleaning a few problem points.

Oh, a discussion how the PCV system works would also be so helpful. Thanks for volunteering.

Looks like my next task is to do the PCV system.

[1997volvo850]

I'm going to check the PTC nipple a lot more frequently than every 60K. You can just pull off the little vacuum hose and see if a drill bit hits gunk.

This is exactly the type of information we need in the tutorial or scheduled maintenance suggestions area. If 60K is too long
to go after XX K miles then we should definitely find a place to add some guidance for other 850 (s70/v70?) owners.

[jblackburn]

The fuel lines are flexible for exactly that reason. You can bend them up and out of the way no problem, just be careful not to un-do the kink in the fuel return line, as it's a bit hard to get back into shape to run past the fuel rail and into the return. I bent them out of the way because they just get in the way.

I left the injectors in place and just swung the entire manifold up. If you've got new seals for them, you just need to give the fuel rail steady pressure with both hands and they will all pop out of place without breaking. Setting them on a cardboard box would probably be fine, that's what I used to hold most of the parts I pulled out.

The hoses are almost a necessity to replace, as I'm sure you'll see, because with the age and heat from the engine, they become EXTREMELY brittle and just break apart when you touch them. I actually broke my idle air control hose in half (not included in the kit by the way), and had to go on a frantic search for one, luckily one of our members here was nice enough to help me out

Now that the cars are older, and as whoa mentioned, the engine internals are starting to wear and increasing crankcase pressure even more, I'd probably check on the PTC every 40-50K or so. That may depend on the amount you drive every year, I put about 20,000 miles/yr on my cars.

I'm going to try to make do with what pictures I have, if anyone has any they took during the procedure, email them to me at [email protected] and I'll include them.

[whoa]

If you remove the clips holding the fuel lines on the top (Torx) and back (10mm) of the engine, you don't need to bend the metal lines at all---though I don't really remember that being a problem with the PCV system replacement, they can be annoying during timing-belt service and certainly if you're pulling off the cam cover.

[1997volvo850]

Has anyone disassembled an old PCT valve?

From what I've read the PCT valve is supposed to stop blowback from the intake in the event of a
backfire. That would imply the valve should shut down given pressure from the air intake side of the
valve,

The vacuum hose attached to the PCT is supposed to close or restrict the passage of gas from the
crankcase to the air intake hose. I don't see anything that would appear to move around in my PCT valve.

It would be great if someone with an old one sitting around disassemble it for the good of the community.

Has anyone tried to modify the valve? Someone mentioned that the PCV system and PCT valve were
designed with a new engine in mind and that our older engines produce much more blow by than the
PCV System can handle.

This makes sense to me that an engine with 200K would produce more blow by than a new engine.
This might also explain why some folks have experienced smoke out the dipstick after completing
the PCV system overhaul.

My car has 230K on it. I'm expecting to see smoke out the dipstick after the PCV overhaul.

Would slightly increasing the size of the hole in the brass end that restricts air flow allow more
gas to escape and compensate for my old engine?

So I'm suggesting increasing the size of the PCT valve until gases stop exhausting out the dipstick.

Let me know if this sounds crazy.

[whoa]

It sounds interesting. I would wonder about the possible effect of that on vacuum---I'm not really clear as to what function the vacuum line to the PTC has, and why it's not a vacuum leak to begin with...

[1997volvo850]

It sounds interesting. I would wonder about the possible effect of that on vacuum---I'm not really clear as to what function the vacuum line to the PTC has, and why it's not a vacuum leak to begin with...

The small vacuum attached to the PCT is supposed to adjust a diaphragm in the PCT valve.
When the engine is idling the vacuum is high in order to lower the air flow with the assumption fewer blow
by gasses are being generated. When the engine is running faster the vacuum is supposed to be less
to allow more gas to escape into the air intake. [less vacuum == high air flow]

This is my understanding of it. There are a few general PCV system documents that do a good job to
outline how the whole system works. A few people here have also described how this works. Maybe I
will post the links I've found.

I would really like to understand how each hose and tube functions in the PCV system. I believe the
holes into the crankcase (top, above oil separator, to right of separator) are to suck blow by gases out
of the engine. The hole below the oil separator is supposed to allow oil that condenses in the oil separator
flow back into the engine. The hose to the PCT valve is where the remaining gases go.

Given this design it seem you shouldn't have to replace the PCV system except for the fact that the
hoses deteriorate. I believe the clogging could be eliminated with regular Seafoam treatments.Very little
oil should collect in the oil separator but should instead return to the oil pan through the lower hole in the block.

Other than this the system should clean itself. I suspect with a regular Seafoam treatments and
a hose solution that does not rot, the PCV system should last forever. What about flexible metal
hoses?

Would really like to see the valve operate...may have to use my shop vac to generate a vacuum...

My gut feeling is that this modification I suggest would not cause serious damage. After I do the PCV
system I will adjust the size of the PCT valve until NO gases are emitted from the dipstick.

I'll let you know if my car blows up...that's if I survive.

[whoa]

Except I don't think there's actually a diaphragm in there, or any moving parts at all. The thing is just hollow, with a heater on one side, the two hose nipples, and the metal plate with the hole in it.

[1997volvo850]

This is how I've seen writeups and posts on the PCT describe the function of the vacuum.

I didn't see anything moveable in my PCT valve (~ 100K old). Would be interesting to play
with a new PCT valve.

Can't imagine the vacuum tube was designed into the PCT for no reason. Descriptions indicate the
vacuum adjusts air flow. Now we need to figure out how it does it.